Mitogens: Substances that stimulate mitosis and lymphocyte transformation. They include not only substances associated with LECTINS, but also substances from streptococci (associated with streptolysin S) and from strains of alpha-toxin-producing staphylococci. (Stedman, 25th ed)Pokeweed Mitogens: Proteins isolated from the roots of the pokeweed, Phytolacca americana, that agglutinate some erythrocytes, stimulate mitosis and antibody synthesis in lymphocytes, and induce activation of plasma cells.Phytohemagglutinins: Mucoproteins isolated from the kidney bean (Phaseolus vulgaris); some of them are mitogenic to lymphocytes, others agglutinate all or certain types of erythrocytes or lymphocytes. They are used mainly in the study of immune mechanisms and in cell culture.Concanavalin A: A MANNOSE/GLUCOSE binding lectin isolated from the jack bean (Canavalia ensiformis). It is a potent mitogen used to stimulate cell proliferation in lymphocytes, primarily T-lymphocyte, cultures.Lymphocyte Activation: Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.Lymphocytes: White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.T-Lymphocytes: Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.B-Lymphocytes: Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.Lectins: Proteins that share the common characteristic of binding to carbohydrates. Some ANTIBODIES and carbohydrate-metabolizing proteins (ENZYMES) also bind to carbohydrates, however they are not considered lectins. PLANT LECTINS are carbohydrate-binding proteins that have been primarily identified by their hemagglutinating activity (HEMAGGLUTININS). However, a variety of lectins occur in animal species where they serve diverse array of functions through specific carbohydrate recognition.Mitogen-Activated Protein Kinases: A superfamily of PROTEIN-SERINE-THREONINE KINASES that are activated by diverse stimuli via protein kinase cascades. They are the final components of the cascades, activated by phosphorylation by MITOGEN-ACTIVATED PROTEIN KINASE KINASES, which in turn are activated by mitogen-activated protein kinase kinase kinases (MAP KINASE KINASE KINASES).Spleen: An encapsulated lymphatic organ through which venous blood filters.Mycoplasma arthritidis: A species of gram-negative bacteria causing purulent POLYARTHRITIS in RATS.Platelet-Derived Growth Factor: Mitogenic peptide growth hormone carried in the alpha-granules of platelets. It is released when platelets adhere to traumatized tissues. Connective tissue cells near the traumatized region respond by initiating the process of replication.Lymphokines: Soluble protein factors generated by activated lymphocytes that affect other cells, primarily those involved in cellular immunity.ThymidineImmunoglobulins: Multi-subunit proteins which function in IMMUNITY. They are produced by B LYMPHOCYTES from the IMMUNOGLOBULIN GENES. They are comprised of two heavy (IMMUNOGLOBULIN HEAVY CHAINS) and two light chains (IMMUNOGLOBULIN LIGHT CHAINS) with additional ancillary polypeptide chains depending on their isoforms. The variety of isoforms include monomeric or polymeric forms, and transmembrane forms (B-CELL ANTIGEN RECEPTORS) or secreted forms (ANTIBODIES). They are divided by the amino acid sequence of their heavy chains into five classes (IMMUNOGLOBULIN A; IMMUNOGLOBULIN D; IMMUNOGLOBULIN E; IMMUNOGLOBULIN G; IMMUNOGLOBULIN M) and various subclasses.Growth Substances: Signal molecules that are involved in the control of cell growth and differentiation.Hemolytic Plaque Technique: A method to identify and enumerate cells that are synthesizing ANTIBODIES against ANTIGENS or HAPTENS conjugated to sheep RED BLOOD CELLS. The sheep red blood cells surrounding cells secreting antibody are lysed by added COMPLEMENT producing a clear zone of HEMOLYSIS. (From Illustrated Dictionary of Immunology, 3rd ed)Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Interleukin-2: A soluble substance elaborated by antigen- or mitogen-stimulated T-LYMPHOCYTES which induces DNA synthesis in naive lymphocytes.Receptors, Mitogen: Glycoprotein molecules on the surface of B- and T-lymphocytes, that react with molecules of antilymphocyte sera, lectins, and other agents which induce blast transformation of lymphocytes.Immunoglobulin M: A class of immunoglobulin bearing mu chains (IMMUNOGLOBULIN MU-CHAINS). IgM can fix COMPLEMENT. The name comes from its high molecular weight and originally being called a macroglobulin.Endothelial Growth Factors: These growth factors are soluble mitogens secreted by a variety of organs. The factors are a mixture of two single chain polypeptides which have affinity to heparin. Their molecular weight are organ and species dependent. They have mitogenic and chemotactic effects and can stimulate endothelial cells to grow and synthesize DNA. The factors are related to both the basic and acidic FIBROBLAST GROWTH FACTORS but have different amino acid sequences.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Rosette Formation: The in vitro formation of clusters consisting of a cell (usually a lymphocyte) surrounded by antigenic cells or antigen-bearing particles (usually erythrocytes, which may or may not be coated with antibody or antibody and complement). The rosette-forming cell may be an antibody-forming cell, a memory cell, a T-cell, a cell bearing surface cytophilic antibodies, or a monocyte possessing Fc receptors. Rosette formation can be used to identify specific populations of these cells.MAP Kinase Signaling System: An intracellular signaling system involving the MAP kinase cascades (three-membered protein kinase cascades). Various upstream activators, which act in response to extracellular stimuli, trigger the cascades by activating the first member of a cascade, MAP KINASE KINASE KINASES; (MAPKKKs). Activated MAPKKKs phosphorylate MITOGEN-ACTIVATED PROTEIN KINASE KINASES which in turn phosphorylate the MITOGEN-ACTIVATED PROTEIN KINASES; (MAPKs). The MAPKs then act on various downstream targets to affect gene expression. In mammals, there are several distinct MAP kinase pathways including the ERK (extracellular signal-regulated kinase) pathway, the SAPK/JNK (stress-activated protein kinase/c-jun kinase) pathway, and the p38 kinase pathway. There is some sharing of components among the pathways depending on which stimulus originates activation of the cascade.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Epidermal Growth Factor: A 6-kDa polypeptide growth factor initially discovered in mouse submaxillary glands. Human epidermal growth factor was originally isolated from urine based on its ability to inhibit gastric secretion and called urogastrone. Epidermal growth factor exerts a wide variety of biological effects including the promotion of proliferation and differentiation of mesenchymal and EPITHELIAL CELLS. It is synthesized as a transmembrane protein which can be cleaved to release a soluble active form.Leukocyte Count: The number of WHITE BLOOD CELLS per unit volume in venous BLOOD. A differential leukocyte count measures the relative numbers of the different types of white cells.Antibody-Producing Cells: Cells of the lymphoid series that can react with antigen to produce specific cell products called antibodies. Various cell subpopulations, often B-lymphocytes, can be defined, based on the different classes of immunoglobulins that they synthesize.Cell Line: Established cell cultures that have the potential to propagate indefinitely.p38 Mitogen-Activated Protein Kinases: A mitogen-activated protein kinase subfamily that regulates a variety of cellular processes including CELL GROWTH PROCESSES; CELL DIFFERENTIATION; APOPTOSIS; and cellular responses to INFLAMMATION. The P38 MAP kinases are regulated by CYTOKINE RECEPTORS and can be activated in response to bacterial pathogens.Vascular Endothelial Growth Factors: A family of angiogenic proteins that are closely-related to VASCULAR ENDOTHELIAL GROWTH FACTOR A. They play an important role in the growth and differentiation of vascular as well as lymphatic endothelial cells.Lymphocyte Cooperation: T-cell enhancement of the B-cell response to thymic-dependent antigens.Antibody Formation: The production of ANTIBODIES by proliferating and differentiated B-LYMPHOCYTES under stimulation by ANTIGENS.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Immunity, Cellular: Manifestations of the immune response which are mediated by antigen-sensitized T-lymphocytes via lymphokines or direct cytotoxicity. This takes place in the absence of circulating antibody or where antibody plays a subordinate role.Enzyme Activation: Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.Mitogen-Activated Protein Kinase 1: A proline-directed serine/threonine protein kinase which mediates signal transduction from the cell surface to the nucleus. Activation of the enzyme by phosphorylation leads to its translocation into the nucleus where it acts upon specific transcription factors. p40 MAPK and p41 MAPK are isoforms.Fibroblast Growth Factors: A family of small polypeptide growth factors that share several common features including a strong affinity for HEPARIN, and a central barrel-shaped core region of 140 amino acids that is highly homologous between family members. Although originally studied as proteins that stimulate the growth of fibroblasts this distinction is no longer a requirement for membership in the fibroblast growth factor family.Superantigens: Microbial antigens that have in common an extremely potent activating effect on T-cells that bear a specific variable region. Superantigens cross-link the variable region with class II MHC proteins regardless of the peptide binding in the T-cell receptor's pocket. The result is a transient expansion and subsequent death and anergy of the T-cells with the appropriate variable regions.Mitogen-Activated Protein Kinase 3: A 44-kDa extracellular signal-regulated MAP kinase that may play a role the initiation and regulation of MEIOSIS; MITOSIS; and postmitotic functions in differentiated cells. It phosphorylates a number of TRANSCRIPTION FACTORS; and MICROTUBULE-ASSOCIATED PROTEINS.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Hepatocyte Growth Factor: Multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. Its receptor is PROTO-ONCOGENE PROTEINS C-MET.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Dose-Response Relationship, Immunologic: A specific immune response elicited by a specific dose of an immunologically active substance or cell in an organism, tissue, or cell.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Vascular Endothelial Growth Factor A: The original member of the family of endothelial cell growth factors referred to as VASCULAR ENDOTHELIAL GROWTH FACTORS. Vascular endothelial growth factor-A was originally isolated from tumor cells and referred to as "tumor angiogenesis factor" and "vascular permeability factor". Although expressed at high levels in certain tumor-derived cells it is produced by a wide variety of cell types. In addition to stimulating vascular growth and vascular permeability it may play a role in stimulating VASODILATION via NITRIC OXIDE-dependent pathways. Alternative splicing of the mRNA for vascular endothelial growth factor A results in several isoforms of the protein being produced.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Kinetics: The rate dynamics in chemical or physical systems.Fibroblasts: Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.Monocytes: Large, phagocytic mononuclear leukocytes produced in the vertebrate BONE MARROW and released into the BLOOD; contain a large, oval or somewhat indented nucleus surrounded by voluminous cytoplasm and numerous organelles.Streptodornase and Streptokinase: A mixture of the enzymes (streptokinase and streptodornase) produced by hemolytic streptococci. It is used topically on surface lesions and by instillation in closed body cavities to remove clotted blood or fibrinous or purulent accumulations. It is also used as a skin test antigen in evaluating generalized cell-mediated immunodeficiency. (Dorland, 27th ed) EC 3.-.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Immune Adherence Reaction: A method for the detection of very small quantities of antibody in which the antigen-antibody-complement complex adheres to indicator cells, usually primate erythrocytes or nonprimate blood platelets. The reaction is dependent on the number of bound C3 molecules on the C3b receptor sites of the indicator cell.Antigens: Substances that are recognized by the immune system and induce an immune reaction.Mice, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations, or by parent x offspring matings carried out with certain restrictions. All animals within an inbred strain trace back to a common ancestor in the twentieth generation.Mitogen-Activated Protein Kinase Kinases: A serine-threonine protein kinase family whose members are components in protein kinase cascades activated by diverse stimuli. These MAPK kinases phosphorylate MITOGEN-ACTIVATED PROTEIN KINASES and are themselves phosphorylated by MAP KINASE KINASE KINASES. JNK kinases (also known as SAPK kinases) are a subfamily.Mice, Inbred BALB CThymus Gland: A single, unpaired primary lymphoid organ situated in the MEDIASTINUM, extending superiorly into the neck to the lower edge of the THYROID GLAND and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat.Tuberculin: A protein extracted from boiled culture of tubercle bacilli (MYCOBACTERIUM TUBERCULOSIS). It is used in the tuberculin skin test (TUBERCULIN TEST) for the diagnosis of tuberculosis infection in asymptomatic persons.Tetradecanoylphorbol Acetate: A phorbol ester found in CROTON OIL with very effective tumor promoting activity. It stimulates the synthesis of both DNA and RNA.Receptors, Antigen, B-Cell: IMMUNOGLOBULINS on the surface of B-LYMPHOCYTES. Their MESSENGER RNA contains an EXON with a membrane spanning sequence, producing immunoglobulins in the form of type I transmembrane proteins as opposed to secreted immunoglobulins (ANTIBODIES) which do not contain the membrane spanning segment.Lymphocyte Culture Test, Mixed: Measure of histocompatibility at the HL-A locus. Peripheral blood lymphocytes from two individuals are mixed together in tissue culture for several days. Lymphocytes from incompatible individuals will stimulate each other to proliferate significantly (measured by tritiated thymidine uptake) whereas those from compatible individuals will not. In the one-way MLC test, the lymphocytes from one of the individuals are inactivated (usually by treatment with MITOMYCIN or radiation) thereby allowing only the untreated remaining population of cells to proliferate in response to foreign histocompatibility antigens.3T3 Cells: Cell lines whose original growing procedure consisted being transferred (T) every 3 days and plated at 300,000 cells per plate (J Cell Biol 17:299-313, 1963). Lines have been developed using several different strains of mice. Tissues are usually fibroblasts derived from mouse embryos but other types and sources have been developed as well. The 3T3 lines are valuable in vitro host systems for oncogenic virus transformation studies, since 3T3 cells possess a high sensitivity to CONTACT INHIBITION.Calcium-Calmodulin-Dependent Protein Kinases: A CALMODULIN-dependent enzyme that catalyzes the phosphorylation of proteins. This enzyme is also sometimes dependent on CALCIUM. A wide range of proteins can act as acceptor, including VIMENTIN; SYNAPSINS; GLYCOGEN SYNTHASE; MYOSIN LIGHT CHAINS; and the MICROTUBULE-ASSOCIATED PROTEINS. (From Enzyme Nomenclature, 1992, p277)T-Lymphocytes, Regulatory: CD4-positive T cells that inhibit immunopathology or autoimmune disease in vivo. They inhibit the immune response by influencing the activity of other cell types. Regulatory T-cells include naturally occurring CD4+CD25+ cells, IL-10 secreting Tr1 cells, and Th3 cells.Fibroblast Growth Factor 7: A fibroblast growth factor that is a specific mitogen for EPITHELIAL CELLS. It binds a complex of HEPARAN SULFATE and FIBROBLAST GROWTH FACTOR RECEPTOR 2B.Leukocytes, Mononuclear: Mature LYMPHOCYTES and MONOCYTES transported by the blood to the body's extravascular space. They are morphologically distinguishable from mature granulocytic leukocytes by their large, non-lobed nuclei and lack of coarse, heavily stained cytoplasmic granules.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Immunosuppression: Deliberate prevention or diminution of the host's immune response. It may be nonspecific as in the administration of immunosuppressive agents (drugs or radiation) or by lymphocyte depletion or may be specific as in desensitization or the simultaneous administration of antigen and immunosuppressive drugs.Dysgammaglobulinemia: An immunologic deficiency state characterized by selective deficiencies of one or more, but not all, classes of immunoglobulins.Phytolacca americana: A plant species of the family PHYTOLACCACEAE. The root has been used in traditional medicine and contains POKEWEED MITOGENS, triterpene glycosides, and antiviral protein.T-Lymphocytes, Helper-Inducer: Subpopulation of CD4+ lymphocytes that cooperate with other lymphocytes (either T or B) to initiate a variety of immune functions. For example, helper-inducer T-cells cooperate with B-cells to produce antibodies to thymus-dependent antigens and with other subpopulations of T-cells to initiate a variety of cell-mediated immune functions.Mice, Inbred C3HLeukemia, Lymphoid: Leukemia associated with HYPERPLASIA of the lymphoid tissues and increased numbers of circulating malignant LYMPHOCYTES and lymphoblasts.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.Extracellular Signal-Regulated MAP Kinases: A mitogen-activated protein kinase subfamily that is widely expressed and plays a role in regulation of MEIOSIS; MITOSIS; and post mitotic functions in differentiated cells. The extracellular signal regulated MAP kinases are regulated by a broad variety of CELL SURFACE RECEPTORS and can be activated by certain CARCINOGENS.Cyclosporins: A group of closely related cyclic undecapeptides from the fungi Trichoderma polysporum and Cylindocarpon lucidum. They have some antineoplastic and antifungal action and significant immunosuppressive effects. Cyclosporins have been proposed as adjuvants in tissue and organ transplantation to suppress graft rejection.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Immune Tolerance: The specific failure of a normally responsive individual to make an immune response to a known antigen. It results from previous contact with the antigen by an immunologically immature individual (fetus or neonate) or by an adult exposed to extreme high-dose or low-dose antigen, or by exposure to radiation, antimetabolites, antilymphocytic serum, etc.Muscle, Smooth, Vascular: The nonstriated involuntary muscle tissue of blood vessels.Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Bombesin: A tetradecapeptide originally obtained from the skins of toads Bombina bombina and B. variegata. It is also an endogenous neurotransmitter in many animals including mammals. Bombesin affects vascular and other smooth muscle, gastric secretion, and renal circulation and function.Agammaglobulinemia: An immunologic deficiency state characterized by an extremely low level of generally all classes of gamma-globulin in the blood.Cell SeparationInterferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Cytokines: Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.Receptors, Interleukin-2: Receptors present on activated T-LYMPHOCYTES and B-LYMPHOCYTES that are specific for INTERLEUKIN-2 and play an important role in LYMPHOCYTE ACTIVATION. They are heterotrimeric proteins consisting of the INTERLEUKIN-2 RECEPTOR ALPHA SUBUNIT, the INTERLEUKIN-2 RECEPTOR BETA SUBUNIT, and the INTERLEUKIN RECEPTOR COMMON GAMMA-CHAIN.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.MAP Kinase Kinase 5: A mitogen-activated protein kinase kinase with specificity for MITOGEN-ACTIVATED PROTEIN KINASE 7.Flavonoids: A group of phenyl benzopyrans named for having structures like FLAVONES.Mice, Inbred C57BLTumor Cells, Cultured: Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.Cell Survival: The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.Antigens, Surface: Antigens on surfaces of cells, including infectious or foreign cells or viruses. They are usually protein-containing groups on cell membranes or walls and may be isolated.Intercellular Signaling Peptides and Proteins: Regulatory proteins and peptides that are signaling molecules involved in the process of PARACRINE COMMUNICATION. They are generally considered factors that are expressed by one cell and are responded to by receptors on another nearby cell. They are distinguished from HORMONES in that their actions are local rather than distal.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Culture Media: Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.Staphylococcal Protein A: A protein present in the cell wall of most Staphylococcus aureus strains. The protein selectively binds to the Fc region of human normal and myeloma-derived IMMUNOGLOBULIN G. It elicits antibody activity and may cause hypersensitivity reactions due to histamine release; has also been used as cell surface antigen marker and in the clinical assessment of B lymphocyte function.Fibroblast Growth Factor 10: A fibroblast growth factor that is a mitogen for KERATINOCYTES. It activates FIBROBLAST GROWTH FACTOR RECEPTOR 2B and is involved in LUNG and limb development.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Ribosomal Protein S6 Kinases, 90-kDa: A family of ribosomal protein S6 kinases that are structurally distinguished from RIBOSOMAL PROTEIN S6 KINASES, 70-KDA by their apparent molecular size and the fact they contain two functional kinase domains. Although considered RIBOSOMAL PROTEIN S6 KINASES, members of this family are activated via the MAP KINASE SIGNALING SYSTEM and have been shown to act on a diverse array of substrates that are involved in cellular regulation such as RIBOSOMAL PROTEIN S6 and CAMP RESPONSE ELEMENT-BINDING PROTEIN.Mycoplasma: A genus of gram-negative, mostly facultatively anaerobic bacteria in the family MYCOPLASMATACEAE. The cells are bounded by a PLASMA MEMBRANE and lack a true CELL WALL. Its organisms are pathogens found on the MUCOUS MEMBRANES of humans, ANIMALS, and BIRDS.Immunologic Deficiency Syndromes: Syndromes in which there is a deficiency or defect in the mechanisms of immunity, either cellular or humoral.Transforming Growth Factor alpha: An EPIDERMAL GROWTH FACTOR related protein that is found in a variety of tissues including EPITHELIUM, and maternal DECIDUA. It is synthesized as a transmembrane protein which can be cleaved to release a soluble active form which binds to the EGF RECEPTOR.Immunoglobulin A: Represents 15-20% of the human serum immunoglobulins, mostly as the 4-chain polymer in humans or dimer in other mammals. Secretory IgA (IMMUNOGLOBULIN A, SECRETORY) is the main immunoglobulin in secretions.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Proto-Oncogene Proteins c-sis: Cellular DNA-binding proteins encoded by the sis gene (GENES, SIS). c-sis proteins make up the B chain of PLATELET-DERIVED GROWTH FACTOR. Overexpression of c-sis causes tumorigenesis.Proto-Oncogene Proteins: Products of proto-oncogenes. Normally they do not have oncogenic or transforming properties, but are involved in the regulation or differentiation of cell growth. They often have protein kinase activity.Endothelium, Vascular: Single pavement layer of cells which line the luminal surface of the entire vascular system and regulate the transport of macromolecules and blood components.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Receptors, Growth Factor: Cell surface receptors that bind growth or trophic factors with high affinity, triggering intracellular responses which influence the growth, differentiation, or survival of cells.Receptors, Cell Surface: Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.Blotting, Northern: Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Interleukin-1: A soluble factor produced by MONOCYTES; MACROPHAGES, and other cells which activates T-lymphocytes and potentiates their response to mitogens or antigens. Interleukin-1 is a general term refers to either of the two distinct proteins, INTERLEUKIN-1ALPHA and INTERLEUKIN-1BETA. The biological effects of IL-1 include the ability to replace macrophage requirements for T-cell activation.Receptors, Platelet-Derived Growth Factor: Specific receptors on cell membranes that react with PLATELET-DERIVED GROWTH FACTOR, its analogs, or antagonists. The alpha PDGF receptor (RECEPTOR, PLATELET-DERIVED GROWTH FACTOR ALPHA) and the beta PDGF receptor (RECEPTOR, PLATELET-DERIVED GROWTH FACTOR BETA) are the two principle types of PDGF receptors. Activation of the protein-tyrosine kinase activity of the receptors occurs by ligand-induced dimerization or heterodimerization of PDGF receptor types.Indomethacin: A non-steroidal anti-inflammatory agent (NSAID) that inhibits the enzyme cyclooxygenase necessary for the formation of prostaglandins and other autacoids. It also inhibits the motility of polymorphonuclear leukocytes.Palatine Tonsil: A round-to-oval mass of lymphoid tissue embedded in the lateral wall of the PHARYNX. There is one on each side of the oropharynx in the fauces between the anterior and posterior pillars of the SOFT PALATE.Insulin, Regular, Pork: Regular insulin preparations that contain the SUS SCROFA insulin peptide sequence.Protein Kinase C: An serine-threonine protein kinase that requires the presence of physiological concentrations of CALCIUM and membrane PHOSPHOLIPIDS. The additional presence of DIACYLGLYCEROLS markedly increases its sensitivity to both calcium and phospholipids. The sensitivity of the enzyme can also be increased by PHORBOL ESTERS and it is believed that protein kinase C is the receptor protein of tumor-promoting phorbol esters.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)Yersinia pseudotuberculosis: A human and animal pathogen causing mesenteric lymphadenitis, diarrhea, and bacteremia.Fibroblast Growth Factor 1: A 17-kDa single-chain polypeptide growth factor that plays a significant role in the process of WOUND HEALING and is a potent inducer of PHYSIOLOGIC ANGIOGENESIS. It binds to HEPARIN, which potentiates its biological activity and protects it from proteolysis. The growth factor is an extremely potent inducer of DNA synthesis in a variety of cell types from mesoderm and neuroectoderm lineages, and also has chemotactic and mitogenic activities. It was originally named acidic fibroblast growth factor based upon its chemical properties and to distinguish it from basic fibroblast growth factor (FIBROBLAST GROWTH FACTOR 2).MAP Kinase Kinase 1: An abundant 43-kDa mitogen-activated protein kinase kinase subtype with specificity for MITOGEN-ACTIVATED PROTEIN KINASE 1 and MITOGEN-ACTIVATED PROTEIN KINASE 3.Hypersensitivity, Delayed: An increased reactivity to specific antigens mediated not by antibodies but by cells.DNA Replication: The process by which a DNA molecule is duplicated.Apoptosis: One of the mechanisms by which CELL DEATH occurs (compare with NECROSIS and AUTOPHAGOCYTOSIS). Apoptosis is the mechanism responsible for the physiological deletion of cells and appears to be intrinsically programmed. It is characterized by distinctive morphologic changes in the nucleus and cytoplasm, chromatin cleavage at regularly spaced sites, and the endonucleolytic cleavage of genomic DNA; (DNA FRAGMENTATION); at internucleosomal sites. This mode of cell death serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth.Butadienes: Four carbon unsaturated hydrocarbons containing two double bonds.Protein-Tyrosine Kinases: Protein kinases that catalyze the PHOSPHORYLATION of TYROSINE residues in proteins with ATP or other nucleotides as phosphate donors.Phosphatidylinositol 3-Kinases: Phosphotransferases that catalyzes the conversion of 1-phosphatidylinositol to 1-phosphatidylinositol 3-phosphate. Many members of this enzyme class are involved in RECEPTOR MEDIATED SIGNAL TRANSDUCTION and regulation of vesicular transport with the cell. Phosphatidylinositol 3-Kinases have been classified both according to their substrate specificity and their mode of action within the cell.AIDS-Related Complex: A prodromal phase of infection with the human immunodeficiency virus (HIV). Laboratory criteria separating AIDS-related complex (ARC) from AIDS include elevated or hyperactive B-cell humoral immune responses, compared to depressed or normal antibody reactivity in AIDS; follicular or mixed hyperplasia in ARC lymph nodes, leading to lymphocyte degeneration and depletion more typical of AIDS; evolving succession of histopathological lesions such as localization of Kaposi's sarcoma, signaling the transition to the full-blown AIDS.Heparin: A highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from six to twenty thousand. Heparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Its function is unknown, but it is used to prevent blood clotting in vivo and vitro, in the form of many different salts.Clone Cells: A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed)Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Cytotoxicity, Immunologic: The phenomenon of target cell destruction by immunologically active effector cells. It may be brought about directly by sensitized T-lymphocytes or by lymphoid or myeloid "killer" cells, or it may be mediated by cytotoxic antibody, cytotoxic factor released by lymphoid cells, or complement.Up-Regulation: A positive regulatory effect on physiological processes at the molecular, cellular, or systemic level. At the molecular level, the major regulatory sites include membrane receptors, genes (GENE EXPRESSION REGULATION), mRNAs (RNA, MESSENGER), and proteins.Pasteurella multocida: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria normally found in the flora of the mouth and respiratory tract of animals and birds. It causes shipping fever (see PASTEURELLOSIS, PNEUMONIC); HEMORRHAGIC BACTEREMIA; and intestinal disease in animals. In humans, disease usually arises from a wound infection following a bite or scratch from domesticated animals.Protein-Serine-Threonine Kinases: A group of enzymes that catalyzes the phosphorylation of serine or threonine residues in proteins, with ATP or other nucleotides as phosphate donors.Lymph Nodes: They are oval or bean shaped bodies (1 - 30 mm in diameter) located along the lymphatic system.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Proto-Oncogene Proteins c-met: Cell surface protein-tyrosine kinase receptors for HEPATOCYTE GROWTH FACTOR. They consist of an extracellular alpha chain which is disulfide-linked to the transmembrane beta chain. The cytoplasmic portion contains the catalytic domain and sites critical for the regulation of kinase activity. Mutations of the gene for PROTO-ONCOGENE PROTEINS C-MET are associated with papillary renal carcinoma and other neoplasia.Mice, Inbred CBACell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Bromodeoxyuridine: A nucleoside that substitutes for thymidine in DNA and thus acts as an antimetabolite. It causes breaks in chromosomes and has been proposed as an antiviral and antineoplastic agent. It has been given orphan drug status for use in the treatment of primary brain tumors.JNK Mitogen-Activated Protein Kinases: A subgroup of mitogen-activated protein kinases that activate TRANSCRIPTION FACTOR AP-1 via the phosphorylation of C-JUN PROTEINS. They are components of intracellular signaling pathways that regulate CELL PROLIFERATION; APOPTOSIS; and CELL DIFFERENTIATION.Receptors, Vascular Endothelial Growth Factor: A family of closely related RECEPTOR PROTEIN-TYROSINE KINASES that bind vascular endothelial growth factors. They share a cluster of seven extracellular Ig-like domains which are important for ligand binding. They are highly expressed in vascular endothelial cells and are critical for the physiological and pathological growth, development and maintenance of blood and lymphatic vessels.CD4-Positive T-Lymphocytes: A critical subpopulation of T-lymphocytes involved in the induction of most immunological functions. The HIV virus has selective tropism for the T4 cell which expresses the CD4 phenotypic marker, a receptor for HIV. In fact, the key element in the profound immunosuppression seen in HIV infection is the depletion of this subset of T-lymphocytes.Protein Kinase Inhibitors: Agents that inhibit PROTEIN KINASES.Nocardia: A genus of gram-positive, aerobic bacteria whose species are widely distributed and are abundant in soil. Some strains are pathogenic opportunists for humans and animals.Saururaceae: A plant family of the order Piperales, subclass Magnoliidae class Magnoliopsida. Members contain sauristolactam, and aristololactam BII.Imidazoles: Compounds containing 1,3-diazole, a five membered aromatic ring containing two nitrogen atoms separated by one of the carbons. Chemically reduced ones include IMIDAZOLINES and IMIDAZOLIDINES. Distinguish from 1,2-diazole (PYRAZOLES).Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.Antigens, CD3: Complex of at least five membrane-bound polypeptides in mature T-lymphocytes that are non-covalently associated with one another and with the T-cell receptor (RECEPTORS, ANTIGEN, T-CELL). The CD3 complex includes the gamma, delta, epsilon, zeta, and eta chains (subunits). When antigen binds to the T-cell receptor, the CD3 complex transduces the activating signals to the cytoplasm of the T-cell. The CD3 gamma and delta chains (subunits) are separate from and not related to the gamma/delta chains of the T-cell receptor (RECEPTORS, ANTIGEN, T-CELL, GAMMA-DELTA).Rats, Inbred BUFAntigens, Differentiation, T-Lymphocyte: Antigens expressed on the cell membrane of T-lymphocytes during differentiation, activation, and normal and neoplastic transformation. Their phenotypic characterization is important in differential diagnosis and studies of thymic ontogeny and T-cell function.Pyridines: Compounds with a six membered aromatic ring containing NITROGEN. The saturated version is PIPERIDINES.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Endothelium: A layer of epithelium that lines the heart, blood vessels (ENDOTHELIUM, VASCULAR), lymph vessels (ENDOTHELIUM, LYMPHATIC), and the serous cavities of the body.Immunoglobulin delta-Chains: The class of heavy chains found in IMMUNOGLOBULIN D. They have a molecular weight of approximately 64 kDa and they contain about 500 amino acid residues arranged in four domains and an oligosaccharide component covalently bound to the Fc fragment constant region.Lymphocyte Subsets: A classification of lymphocytes based on structurally or functionally different populations of cells.Genes, fos: Retrovirus-associated DNA sequences (fos) originally isolated from the Finkel-Biskis-Jinkins (FBJ-MSV) and Finkel-Biskis-Reilly (FBR-MSV) murine sarcoma viruses. The proto-oncogene protein c-fos codes for a nuclear protein which is involved in growth-related transcriptional control. The insertion of c-fos into FBJ-MSV or FBR-MSV induces osteogenic sarcomas in mice. The human c-fos gene is located at 14q21-31 on the long arm of chromosome 14.Nitriles: Organic compounds containing the -CN radical. The concept is distinguished from CYANIDES, which denotes inorganic salts of HYDROGEN CYANIDE.IgA Deficiency: A dysgammaglobulinemia characterized by a deficiency of IMMUNOGLOBULIN A.MAP Kinase Kinase Kinases: Mitogen-activated protein kinase kinase kinases (MAPKKKs) are serine-threonine protein kinases that initiate protein kinase signaling cascades. They phosphorylate MITOGEN-ACTIVATED PROTEIN KINASE KINASES; (MAPKKs) which in turn phosphorylate MITOGEN-ACTIVATED PROTEIN KINASES; (MAPKs).Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Molecular Weight: The sum of the weight of all the atoms in a molecule.Receptors, Fibroblast Growth Factor: Specific molecular sites or structures on cell membranes that react with FIBROBLAST GROWTH FACTORS (both the basic and acidic forms), their analogs, or their antagonists to elicit or to inhibit the specific response of the cell to these factors. These receptors frequently possess tyrosine kinase activity.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Peptides: Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are linear polypeptides that are normally synthesized on RIBOSOMES.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Lysophospholipids: Derivatives of PHOSPHATIDIC ACIDS that lack one of its fatty acyl chains due to its hydrolytic removal.Cell Movement: The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.Insulin-Like Growth Factor I: A well-characterized basic peptide believed to be secreted by the liver and to circulate in the blood. It has growth-regulating, insulin-like, and mitogenic activities. This growth factor has a major, but not absolute, dependence on GROWTH HORMONE. It is believed to be mainly active in adults in contrast to INSULIN-LIKE GROWTH FACTOR II, which is a major fetal growth factor.Genes, jun: Retrovirus-associated DNA sequences (jun) originally isolated from the avian sarcoma virus 17 (ASV 17). The proto-oncogene jun (c-jun) codes for a nuclear protein which is involved in growth-related transcriptional control. Insertion of c-jun into ASV-17 or the constitutive expression of the c-jun protein produces tumorgenicity. The human c-jun gene is located at 1p31-32 on the short arm of chromosome 1.Immunocompetence: The ability of lymphoid cells to mount a humoral or cellular immune response when challenged by antigen.Leukocytes: White blood cells. These include granular leukocytes (BASOPHILS; EOSINOPHILS; and NEUTROPHILS) as well as non-granular leukocytes (LYMPHOCYTES and MONOCYTES).Tumor Necrosis Factor-alpha: Serum glycoprotein produced by activated MACROPHAGES and other mammalian MONONUCLEAR LEUKOCYTES. It has necrotizing activity against tumor cell lines and increases ability to reject tumor transplants. Also known as TNF-alpha, it is only 30% homologous to TNF-beta (LYMPHOTOXIN), but they share TNF RECEPTORS.Antibodies: Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).Cell Adhesion: Adherence of cells to surfaces or to other cells.Tissue Extracts: Preparations made from animal tissues or organs (ANIMAL STRUCTURES). They usually contain many components, any one of which may be pharmacologically or physiologically active. Tissue extracts may contain specific, but uncharacterized factors or proteins with specific actions.Thrombin: An enzyme formed from PROTHROMBIN that converts FIBRINOGEN to FIBRIN.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Ribosomal Protein S6 Kinases: A family of protein serine/threonine kinases which act as intracellular signalling intermediates. Ribosomal protein S6 kinases are activated through phosphorylation in response to a variety of HORMONES and INTERCELLULAR SIGNALING PEPTIDES AND PROTEINS. Phosphorylation of RIBOSOMAL PROTEIN S6 by enzymes in this class results in increased expression of 5' top MRNAs. Although specific for RIBOSOMAL PROTEIN S6 members of this class of kinases can act on a number of substrates within the cell. The immunosuppressant SIROLIMUS inhibits the activation of ribosomal protein S6 kinases.Protein Kinases: A family of enzymes that catalyze the conversion of ATP and a protein to ADP and a phosphoprotein.Immunoblotting: Immunologic method used for detecting or quantifying immunoreactive substances. The substance is identified by first immobilizing it by blotting onto a membrane and then tagging it with labeled antibodies.Stimulation, Chemical: The increase in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.Cyclin D1: Protein encoded by the bcl-1 gene which plays a critical role in regulating the cell cycle. Overexpression of cyclin D1 is the result of bcl-1 rearrangement, a t(11;14) translocation, and is implicated in various neoplasms.Killer Cells, Natural: Bone marrow-derived lymphocytes that possess cytotoxic properties, classically directed against transformed and virus-infected cells. Unlike T CELLS; and B CELLS; NK CELLS are not antigen specific. The cytotoxicity of natural killer cells is determined by the collective signaling of an array of inhibitory and stimulatory CELL SURFACE RECEPTORS. A subset of T-LYMPHOCYTES referred to as NATURAL KILLER T CELLS shares some of the properties of this cell type.Cell Line, Tumor: A cell line derived from cultured tumor cells.