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HLA Antigens: Antigens determined by leukocyte loci found on chromosome 6, the major histocompatibility loci in humans. They are polypeptides or glycoproteins found on most nucleated cells and platelets, determine tissue types for transplantation, and are associated with certain diseases.HLA-DR3 Antigen: An HLA-DR antigen which is associated with HLA-DRB1 CHAINS encoded by DRB1*03 alleles.HLA-DR Antigens: A subclass of HLA-D antigens that consist of alpha and beta chains. The inheritance of HLA-DR antigens differs from that of the HLA-DQ ANTIGENS and HLA-DP ANTIGENS.Antigens: Substances that are recognized by the immune system and induce an immune reaction.HLA-DR4 Antigen: An HLA-DR antigen which is associated with HLA-DRB1 CHAINS encoded by DRB1*04 alleles.HLA-DR Serological Subtypes: HLA-DR antigen subtypes that have been classified according to their affinity to specific ANTIBODIES. The DNA sequence analyses of HLA-DR ALPHA-CHAINS and HLA-DR BETA-CHAINS has for the most part revealed the specific alleles that are responsible for each serological subtype.HLA-DQ Antigens: A group of the D-related HLA antigens found to differ from the DR antigens in genetic locus and therefore inheritance. These antigens are polymorphic glycoproteins comprising alpha and beta chains and are found on lymphoid and other cells, often associated with certain diseases.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.HLA-DR2 Antigen: A broad specificity HLA-DR antigen that is associated with HLA-DRB1 CHAINS encoded by DRB1*01:15 and DRB1*01:16 alleles.Antigens, Neoplasm: Proteins, glycoprotein, or lipoprotein moieties on surfaces of tumor cells that are usually identified by monoclonal antibodies. Many of these are of either embryonic or viral origin.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.Antigens, Viral: Substances elaborated by viruses that have antigenic activity.Histocompatibility Antigens Class II: Large, transmembrane, non-covalently linked glycoproteins (alpha and beta). Both chains can be polymorphic although there is more structural variation in the beta chains. The class II antigens in humans are called HLA-D ANTIGENS and are coded by a gene on chromosome 6. In mice, two genes named IA and IE on chromosome 17 code for the H-2 antigens. The antigens are found on B-lymphocytes, macrophages, epidermal cells, and sperm and are thought to mediate the competence of and cellular cooperation in the immune response. The term IA antigens used to refer only to the proteins encoded by the IA genes in the mouse, but is now used as a generic term for any class II histocompatibility antigen.HLA-DR7 Antigen: A HLA-DR antigen that is associated with HLA-DRB1 CHAINS encoded by DRB1*07 alleles.Histocompatibility Testing: Identification of the major histocompatibility antigens of transplant DONORS and potential recipients, usually by serological tests. Donor and recipient pairs should be of identical ABO blood group, and in addition should be matched as closely as possible for HISTOCOMPATIBILITY ANTIGENS in order to minimize the likelihood of allograft rejection. (King, Dictionary of Genetics, 4th ed)Keratoconjunctivitis Sicca: Drying and inflammation of the conjunctiva as a result of insufficient lacrimal secretion. When found in association with XEROSTOMIA and polyarthritis, it is called SJOGREN'S SYNDROME.HLA-DR1 Antigen: An HLA-DR antigen associated with HLA-DRB1 CHAINS that are encoded by DRB1*01 alleles.Gold Sodium Thiomalate: A variable mixture of the mono- and disodium salts of gold thiomalic acid used mainly for its anti-inflammatory action in the treatment of rheumatoid arthritis. It is most effective in active progressive rheumatoid arthritis and of little or no value in the presence of extensive deformities or in the treatment of other forms of arthritis.Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.HLA-DRB1 Chains: A subtype of HLA-DRB beta chains that includes over one hundred allele variants. The HLA-DRB1 subtype is associated with several of the HLA-DR SEROLOGICAL SUBTYPES.Epitopes: Sites on an antigen that interact with specific antibodies.Antigens, Polyomavirus Transforming: Polyomavirus antigens which cause infection and cellular transformation. The large T antigen is necessary for the initiation of viral DNA synthesis, repression of transcription of the early region and is responsible in conjunction with the middle T antigen for the transformation of primary cells. Small T antigen is necessary for the completion of the productive infection cycle.Genes, MHC Class II: Genetic loci in the vertebrate major histocompatibility complex that encode polymorphic products which control the immune response to specific antigens. The genes are found in the HLA-D region in humans and in the I region in mice.Antigens, CD: Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation.Antigens, Fungal: Substances of fungal origin that have antigenic activity.HLA-A Antigens: Polymorphic class I human histocompatibility (HLA) surface antigens present on almost all nucleated cells. At least 20 antigens have been identified which are encoded by the A locus of multiple alleles on chromosome 6. They serve as targets for T-cell cytolytic responses and are involved with acceptance or rejection of tissue/organ grafts.HLA-B Antigens: Class I human histocompatibility (HLA) surface antigens encoded by more than 30 detectable alleles on locus B of the HLA complex, the most polymorphic of all the HLA specificities. Several of these antigens (e.g., HLA-B27, -B7, -B8) are strongly associated with predisposition to rheumatoid and other autoimmune disorders. Like other class I HLA determinants, they are involved in the cellular immune reactivity of cytolytic T lymphocytes.Antigens, Helminth: Any part or derivative of a helminth that elicits an immune reaction. The most commonly seen helminth antigens are those of the schistosomes.H-2 Antigens: The major group of transplantation antigens in the mouse.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Epitopes, T-Lymphocyte: Antigenic determinants recognized and bound by the T-cell receptor. Epitopes recognized by the T-cell receptor are often located in the inner, unexposed side of the antigen, and become accessible to the T-cell receptors after proteolytic processing of the antigen.Histocompatibility Antigens Class I: Membrane glycoproteins consisting of an alpha subunit and a BETA 2-MICROGLOBULIN beta subunit. In humans, highly polymorphic genes on CHROMOSOME 6 encode the alpha subunits of class I antigens and play an important role in determining the serological specificity of the surface antigen. Class I antigens are found on most nucleated cells and are generally detected by their reactivity with alloantisera. These antigens are recognized during GRAFT REJECTION and restrict cell-mediated lysis of virus-infected cells.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.Carcinoembryonic Antigen: A glycoprotein that is secreted into the luminal surface of the epithelia in the gastrointestinal tract. It is found in the feces and pancreaticobiliary secretions and is used to monitor the response to colon cancer treatment.Antigens, Viral, Tumor: Those proteins recognized by antibodies from serum of animals bearing tumors induced by viruses; these proteins are presumably coded for by the nucleic acids of the same viruses that caused the neoplastic transformation.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.Histocompatibility Antigens: A group of antigens that includes both the major and minor histocompatibility antigens. The former are genetically determined by the major histocompatibility complex. They determine tissue type for transplantation and cause allograft rejections. The latter are systems of allelic alloantigens that can cause weak transplant rejection.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.HLA-D Antigens: Human immune-response or Class II antigens found mainly, but not exclusively, on B-lymphocytes and produced from genes of the HLA-D locus. They are extremely polymorphic families of glycopeptides, each consisting of two chains, alpha and beta. This group of antigens includes the -DR, -DQ and -DP designations, of which HLA-DR is most studied; some of these glycoproteins are associated with certain diseases, possibly of immune etiology.Receptors, Antigen, T-Cell: Molecules on the surface of T-lymphocytes that recognize and combine with antigens. The receptors are non-covalently associated with a complex of several polypeptides collectively called CD3 antigens (ANTIGENS, CD3). Recognition of foreign antigen and the major histocompatibility complex is accomplished by a single heterodimeric antigen-receptor structure, composed of either alpha-beta (RECEPTORS, ANTIGEN, T-CELL, ALPHA-BETA) or gamma-delta (RECEPTORS, ANTIGEN, T-CELL, GAMMA-DELTA) chains.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.HLA-A2 Antigen: A specific HLA-A surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-A*02 allele family.Diabetes Mellitus, Type 1: A subtype of DIABETES MELLITUS that is characterized by INSULIN deficiency. It is manifested by the sudden onset of severe HYPERGLYCEMIA, rapid progression to DIABETIC KETOACIDOSIS, and DEATH unless treated with insulin. The disease may occur at any age, but is most common in childhood or adolescence.Haplotypes: The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX.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.Proliferating Cell Nuclear Antigen: Nuclear antigen with a role in DNA synthesis, DNA repair, and cell cycle progression. PCNA is required for the coordinated synthesis of both leading and lagging strands at the replication fork during DNA replication. PCNA expression correlates with the proliferation activity of several malignant and non-malignant cell types.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.Prostate-Specific Antigen: A glycoprotein that is a kallikrein-like serine proteinase and an esterase, produced by epithelial cells of both normal and malignant prostate tissue. It is an important marker for the diagnosis of prostate cancer.O Antigens: The lipopolysaccharide-protein somatic antigens, usually from gram-negative bacteria, important in the serological classification of enteric bacilli. The O-specific chains determine the specificity of the O antigens of a given serotype. O antigens are the immunodominant part of the lipopolysaccharide molecule in the intact bacterial cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Arthritis, Rheumatoid: A chronic systemic disease, primarily of the joints, marked by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Etiology is unknown, but autoimmune mechanisms have been implicated.Dipeptidyl Peptidase 4: A serine protease that catalyses the release of an N-terminal dipeptide. Several biologically-active peptides have been identified as dipeptidyl peptidase 4 substrates including INCRETINS; NEUROPEPTIDES; and CHEMOKINES. The protein is also found bound to ADENOSINE DEAMINASE on the T-CELL surface and is believed to play a role in T-cell activation.Antigens, CD8: Differentiation antigens found on thymocytes and on cytotoxic and suppressor T-lymphocytes. CD8 antigens are members of the immunoglobulin supergene family and are associative recognition elements in MHC (Major Histocompatibility Complex) Class I-restricted interactions.Antigens, CD15: A trisaccharide antigen expressed on glycolipids and many cell-surface glycoproteins. In the blood the antigen is found on the surface of NEUTROPHILS; EOSINOPHILS; and MONOCYTES. In addition, CD15 antigen is a stage-specific embryonic antigen.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.Antigens, Tumor-Associated, Carbohydrate: Carbohydrate antigens expressed by malignant tissue. They are useful as tumor markers and are measured in the serum by means of a radioimmunoassay employing monoclonal antibodies.Cross Reactions: Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Blood Group Antigens: Sets of cell surface antigens located on BLOOD CELLS. They are usually membrane GLYCOPROTEINS or GLYCOLIPIDS that are antigenically distinguished by their carbohydrate moieties.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.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).Hepatitis B Surface Antigens: Those hepatitis B antigens found on the surface of the Dane particle and on the 20 nm spherical and tubular particles. Several subspecificities of the surface antigen are known. These were formerly called the Australia antigen.Genetic Predisposition to Disease: A latent susceptibility to disease at the genetic level, which may be activated under certain conditions.HLA-C Antigens: Class I human histocompatibility (HLA) antigens encoded by a small cluster of structural genes at the C locus on chromosome 6. They have significantly lower immunogenicity than the HLA-A and -B determinants and are therefore of minor importance in donor/recipient crossmatching. Their primary role is their high-risk association with certain disease manifestations (e.g., spondylarthritis, psoriasis, multiple myeloma).Antibody Specificity: The property of antibodies which enables them to react with some ANTIGENIC DETERMINANTS and not with others. Specificity is dependent on chemical composition, physical forces, and molecular structure at the binding site.Mice, Inbred BALB CHLA-DQ beta-Chains: Transmembrane proteins that form the beta subunits of the HLA-DQ antigens.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Antigens, CD4: 55-kDa antigens found on HELPER-INDUCER T-LYMPHOCYTES and on a variety of other immune cell types. CD4 antigens are members of the immunoglobulin supergene family and are implicated as associative recognition elements in MAJOR HISTOCOMPATIBILITY COMPLEX class II-restricted immune responses. On T-lymphocytes they define the helper/inducer subset. CD4 antigens also serve as INTERLEUKIN-15 receptors and bind to the HIV receptors, binding directly to the HIV ENVELOPE PROTEIN GP120.Antigens, CD45: High-molecular weight glycoproteins uniquely expressed on the surface of LEUKOCYTES and their hemopoietic progenitors. They contain a cytoplasmic protein tyrosine phosphatase activity which plays a role in intracellular signaling from the CELL SURFACE RECEPTORS. The CD45 antigens occur as multiple isoforms that result from alternative mRNA splicing and differential usage of three exons.Fluorescent Antibody Technique: Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (FLUORESCENT ANTIBODY TECHNIQUE, DIRECT) or an indirect method, by formation of antigen-antibody complex which is then labeled with fluorescein-conjugated anti-immunoglobulin antibody (FLUORESCENT ANTIBODY TECHNIQUE, INDIRECT). The tissue is then examined by fluorescence microscopy.Receptors, Antigen: Molecules on the surface of B- and T-lymphocytes that recognize and combine with specific antigens.Antigen-Antibody Reactions: The processes triggered by interactions of ANTIBODIES with their ANTIGENS.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.Hepatitis B Antigens: Antigens of the virion of the HEPATITIS B VIRUS or the Dane particle, its surface (HEPATITIS B SURFACE ANTIGENS), core (HEPATITIS B CORE ANTIGENS), and other associated antigens, including the HEPATITIS B E ANTIGENS.Antibody Formation: The production of ANTIBODIES by proliferating and differentiated B-LYMPHOCYTES under stimulation by ANTIGENS.T-Lymphocytes, Cytotoxic: Immunized T-lymphocytes which can directly destroy appropriate target cells. These cytotoxic lymphocytes may be generated in vitro in mixed lymphocyte cultures (MLC), in vivo during a graft-versus-host (GVH) reaction, or after immunization with an allograft, tumor cell or virally transformed or chemically modified target cell. The lytic phenomenon is sometimes referred to as cell-mediated lympholysis (CML). These CD8-positive cells are distinct from NATURAL KILLER CELLS and NATURAL KILLER T-CELLS. There are two effector phenotypes: TC1 and TC2.Antigens, CD1: Glycoproteins expressed on cortical thymocytes and on some dendritic cells and B-cells. Their structure is similar to that of MHC Class I and their function has been postulated as similar also. CD1 antigens are highly specific markers for human LANGERHANS CELLS.Immune Sera: Serum that contains antibodies. It is obtained from an animal that has been immunized either by ANTIGEN injection or infection with microorganisms containing the antigen.Immunization: Deliberate stimulation of the host's immune response. ACTIVE IMMUNIZATION involves administration of ANTIGENS or IMMUNOLOGIC ADJUVANTS. PASSIVE IMMUNIZATION involves administration of IMMUNE SERA or LYMPHOCYTES or their extracts (e.g., transfer factor, immune RNA) or transplantation of immunocompetent cell producing tissue (thymus or bone marrow).HLA-A1 Antigen: A specific HLA-A surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-A*01 allele family.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Antigens, Differentiation: Antigens expressed primarily on the membranes of living cells during sequential stages of maturation and differentiation. As immunologic markers they have high organ and tissue specificity and are useful as probes in studies of normal cell development as well as neoplastic transformation.Antigens, 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.HLA-B7 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*07 allele family.HLA-B27 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*27 allele family.HLA-B8 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*08 allele family.Major Histocompatibility Complex: The genetic region which contains the loci of genes which determine the structure of the serologically defined (SD) and lymphocyte-defined (LD) TRANSPLANTATION ANTIGENS, genes which control the structure of the IMMUNE RESPONSE-ASSOCIATED ANTIGENS, HUMAN; the IMMUNE RESPONSE GENES which control the ability of an animal to respond immunologically to antigenic stimuli, and genes which determine the structure and/or level of the first four components of complement.HIV Antigens: Antigens associated with specific proteins of the human adult T-cell immunodeficiency virus (HIV); also called HTLV-III-associated and lymphadenopathy-associated virus (LAV) antigens.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.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.MART-1 Antigen: A melanosome-specific protein that plays a role in the expression, stability, trafficking, and processing of GP100 MELANOMA ANTIGEN, which is critical to the formation of Stage II MELANOSOMES. The protein is used as an antigen marker for MELANOMA cells.Antigens, CD80: A costimulatory ligand expressed by ANTIGEN-PRESENTING CELLS that binds to CTLA-4 ANTIGEN with high specificity and to CD28 ANTIGEN with low specificity. The interaction of CD80 with CD28 ANTIGEN provides a costimulatory signal to T-LYMPHOCYTES, while its interaction with CTLA-4 ANTIGEN may play a role in inducing PERIPHERAL TOLERANCE.Autoantigens: Endogenous tissue constituents that have the ability to interact with AUTOANTIBODIES and cause an immune response.Immunoenzyme Techniques: Immunologic techniques based on the use of: (1) enzyme-antibody conjugates; (2) enzyme-antigen conjugates; (3) antienzyme antibody followed by its homologous enzyme; or (4) enzyme-antienzyme complexes. These are used histologically for visualizing or labeling tissue specimens.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).Genes, MHC Class I: Genetic loci in the vertebrate major histocompatibility complex which encode polymorphic characteristics not related to immune responsiveness or complement activity, e.g., B loci (chicken), DLA (dog), GPLA (guinea pig), H-2 (mouse), RT-1 (rat), HLA-A, -B, and -C class I genes of man.Epstein-Barr Virus Nuclear Antigens: Nuclear antigens encoded by VIRAL GENES found in HUMAN HERPESVIRUS 4. At least six nuclear antigens have been identified.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.Antigen-Presenting Cells: A heterogeneous group of immunocompetent cells that mediate the cellular immune response by processing and presenting antigens to the T-cells. Traditional antigen-presenting cells include MACROPHAGES; DENDRITIC CELLS; LANGERHANS CELLS; and B-LYMPHOCYTES. FOLLICULAR DENDRITIC CELLS are not traditional antigen-presenting cells, but because they hold antigen on their cell surface in the form of IMMUNE COMPLEXES for B-cell recognition they are considered so by some authors.Antigens, Heterophile: Antigens stimulating the formation of, or combining with heterophile antibodies. They are cross-reacting antigens found in phylogenetically unrelated species.Interferon-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.HLA-B44 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*44 allele family.Mice, Inbred C57BLAntigens, CD19: Differentiation antigens expressed on B-lymphocytes and B-cell precursors. They are involved in regulation of B-cell proliferation.DNA Probes, HLA: DNA probes specific for the human leukocyte antigen genes, which represent the major histocompatibility determinants in humans. The four known loci are designated as A, B, C, and D. Specific antigens are identified by a locus notation and number, e.g., HLA-A11. The inheritance of certain HLA alleles is associated with increased risk for certain diseases (e.g., insulin-dependent diabetes mellitus).CD8-Positive T-Lymphocytes: A critical subpopulation of regulatory T-lymphocytes involved in MHC Class I-restricted interactions. They include both cytotoxic T-lymphocytes (T-LYMPHOCYTES, CYTOTOXIC) and CD8+ suppressor T-lymphocytes.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.Spleen: An encapsulated lymphatic organ through which venous blood filters.Hepatitis B Core Antigens: The hepatitis B antigen within the core of the Dane particle, the infectious hepatitis virion.Autoantibodies: Antibodies that react with self-antigens (AUTOANTIGENS) of the organism that produced them.Antigens, CD40: A member of the tumor necrosis factor receptor superfamily with specificity for CD40 LIGAND. It is found on mature B-LYMPHOCYTES and some EPITHELIAL CELLS, lymphoid DENDRITIC CELLS. Evidence suggests that CD40-dependent activation of B-cells is important for generation of memory B-cells within the germinal centers. Mutations of the gene for CD40 antigen result in HYPER-IGM IMMUNODEFICIENCY SYNDROME, TYPE 3. Signaling of the receptor occurs through its association with TNF RECEPTOR-ASSOCIATED FACTORS.HLA-DR5 Antigen: A broad-specificity HLA-DR antigen that is associated with HLA-DRB1 CHAINS encoded by DRB1*11 and DRB1*12 alleles.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.Isoantibodies: Antibodies from an individual that react with ISOANTIGENS of another individual of the same species.Antigen-Antibody Complex: The complex formed by the binding of antigen and antibody molecules. The deposition of large antigen-antibody complexes leading to tissue damage causes IMMUNE COMPLEX DISEASES.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)Receptors, Antigen, T-Cell, alpha-beta: T-cell receptors composed of CD3-associated alpha and beta polypeptide chains and expressed primarily in CD4+ or CD8+ T-cells. Unlike immunoglobulins, the alpha-beta T-cell receptors recognize antigens only when presented in association with major histocompatibility (MHC) molecules.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.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.H-Y Antigen: A sex-specific cell surface antigen produced by the sex-determining gene of the Y chromosome in mammals. It causes syngeneic grafts from males to females to be rejected and interacts with somatic elements of the embryologic undifferentiated gonad to produce testicular organogenesis.Immunodiffusion: Technique involving the diffusion of antigen or antibody through a semisolid medium, usually agar or agarose gel, with the result being a precipitin reaction.Molecular Weight: The sum of the weight of all the atoms in a molecule.HLA-B35 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*35 allele family.Antigens, Thy-1: A group of differentiation surface antigens, among the first to be discovered on thymocytes and T-lymphocytes. Originally identified in the mouse, they are also found in other species including humans, and are expressed on brain neurons and other cells.Forssman Antigen: A glycolipid, cross-species antigen that induces production of antisheep hemolysin. It is present on the tissue cells of many species but absent in humans. It is found in many infectious agents.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.Antigens, CD86: A costimulatory ligand expressed by ANTIGEN-PRESENTING CELLS that binds to CD28 ANTIGEN with high specificity and to CTLA-4 ANTIGEN with low specificity. The interaction of CD86 with CD28 ANTIGEN provides a stimulatory signal to T-LYMPHOCYTES, while its interaction with CTLA-4 ANTIGEN may play a role in inducing PERIPHERAL TOLERANCE.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Dendritic Cells: Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as SKIN and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process ANTIGENS, and present them to T-CELLS, thereby stimulating CELL-MEDIATED IMMUNITY. They are different from the non-hematopoietic FOLLICULAR DENDRITIC CELLS, which have a similar morphology and immune system function, but with respect to humoral immunity (ANTIBODY PRODUCTION).Complement Fixation Tests: Serologic tests based on inactivation of complement by the antigen-antibody complex (stage 1). Binding of free complement can be visualized by addition of a second antigen-antibody system such as red cells and appropriate red cell antibody (hemolysin) requiring complement for its completion (stage 2). Failure of the red cells to lyse indicates that a specific antigen-antibody reaction has taken place in stage 1. If red cells lyse, free complement is present indicating no antigen-antibody reaction occurred in stage 1.HLA-A3 Antigen: A specific HLA-A surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-A*03 allele family.CTLA-4 Antigen: An inhibitory T CELL receptor that is closely related to CD28 ANTIGEN. It has specificity for CD80 ANTIGEN and CD86 ANTIGEN and acts as a negative regulator of peripheral T cell function. CTLA-4 antigen is believed to play role in inducing PERIPHERAL TOLERANCE.HLA-A24 Antigen: A specific HLA-A surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-A*24 allele family.Ovalbumin: An albumin obtained from the white of eggs. It is a member of the serpin superfamily.Simian virus 40: A species of POLYOMAVIRUS originally isolated from Rhesus monkey kidney tissue. It produces malignancy in human and newborn hamster kidney cell cultures.Antibodies, Viral: Immunoglobulins produced in response to VIRAL ANTIGENS.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.gp100 Melanoma Antigen: A melanosome-associated protein that plays a role in the maturation of the MELANOSOME.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.Membrane Glycoproteins: Glycoproteins found on the membrane or surface of cells.Immunoelectrophoresis: A technique that combines protein electrophoresis and double immunodiffusion. In this procedure proteins are first separated by gel electrophoresis (usually agarose), then made visible by immunodiffusion of specific antibodies. A distinct elliptical precipitin arc results for each protein detectable by the antisera.HLA-DP Antigens: A group of the D-related HLA antigens (human) found to differ from the DR antigens in genetic locus and therefore inheritance. These antigens are polymorphic glycoproteins comprising alpha and beta chains and are found on lymphoid and other cells, often associated with certain diseases.HLA-DQ alpha-Chains: Transmembrane proteins that form the alpha subunits of the HLA-DQ antigens.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Receptors, TNF-Related Apoptosis-Inducing Ligand: Tumor necrosis factor receptor family members that are widely expressed and play a role in regulation of peripheral immune responses and APOPTOSIS. The receptors are specific for TNF-RELATED APOPTOSIS-INDUCING LIGAND and signal via conserved death domains that associate with specific TNF RECEPTOR-ASSOCIATED FACTORS in the CYTOPLASM.Isoantigens: Antigens that exist in alternative (allelic) forms in a single species. When an isoantigen is encountered by species members who lack it, an immune response is induced. Typical isoantigens are the BLOOD GROUP ANTIGENS.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Tumor 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.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Antigens, CD95: A tumor necrosis factor receptor subtype found in a variety of tissues and on activated LYMPHOCYTES. It has specificity for FAS LIGAND and plays a role in regulation of peripheral immune responses and APOPTOSIS. Multiple isoforms of the protein exist due to multiple ALTERNATIVE SPLICING. The activated receptor signals via a conserved death domain that associates with specific TNF RECEPTOR-ASSOCIATED FACTORS in the CYTOPLASM.Serologic Tests: Diagnostic procedures involving immunoglobulin reactions.Minor Histocompatibility Antigens: Allelic alloantigens often responsible for weak graft rejection in cases when (major) histocompatibility has been established by standard tests. In the mouse they are coded by more than 500 genes at up to 30 minor histocompatibility loci. The most well-known minor histocompatibility antigen in mammals is the H-Y antigen.Antigens, CD79: A component of the B-cell antigen receptor that is involved in B-cell antigen receptor heavy chain transport to the PLASMA MEMBRANE. It is expressed almost exclusively in B-LYMPHOCYTES and serves as a useful marker for B-cell NEOPLASMS.Histocompatibility: The degree of antigenic similarity between the tissues of different individuals, which determines the acceptance or rejection of allografts.CA-19-9 Antigen: Sialylated Lewis blood group carbohydrate antigen found in many adenocarcinomas of the digestive tract, especially pancreatic tumors.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.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Hybridomas: Cells artificially created by fusion of activated lymphocytes with neoplastic cells. The resulting hybrid cells are cloned and produce pure MONOCLONAL ANTIBODIES or T-cell products, identical to those produced by the immunologically competent parent cell.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Hemagglutination Tests: Sensitive tests to measure certain antigens, antibodies, or viruses, using their ability to agglutinate certain erythrocytes. (From Stedman, 26th ed)Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Antigens, CD2: Glycoprotein members of the immunoglobulin superfamily which participate in T-cell adhesion and activation. They are expressed on most peripheral T-lymphocytes, natural killer cells, and thymocytes, and function as co-receptors or accessory molecules in the T-cell receptor complex.Lewis Blood-Group System: A group of dominantly and independently inherited antigens associated with the ABO blood factors. They are glycolipids present in plasma and secretions that may adhere to the erythrocytes. The phenotype Le(b) is the result of the interaction of the Le gene Le(a) with the genes for the ABO blood groups.Cytotoxicity Tests, Immunologic: The demonstration of the cytotoxic effect on a target cell of a lymphocyte, a mediator released by a sensitized lymphocyte, an antibody, or complement.Peptide Fragments: Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.HLA-DP beta-Chains: Transmembrane proteins that form the beta subunits of the HLA-DP antigens.Ki-67 Antigen: A CELL CYCLE and tumor growth marker which can be readily detected using IMMUNOCYTOCHEMISTRY methods. Ki-67 is a nuclear antigen present only in the nuclei of cycling cells.Melanoma: A malignant neoplasm derived from cells that are capable of forming melanin, which may occur in the skin of any part of the body, in the eye, or, rarely, in the mucous membranes of the genitalia, anus, oral cavity, or other sites. It occurs mostly in adults and may originate de novo or from a pigmented nevus or malignant lentigo. Melanomas frequently metastasize widely, and the regional lymph nodes, liver, lungs, and brain are likely to be involved. The incidence of malignant skin melanomas is rising rapidly in all parts of the world. (Stedman, 25th ed; from Rook et al., Textbook of Dermatology, 4th ed, p2445)Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Hepatitis B e Antigens: A closely related group of antigens found in the plasma only during the infective phase of hepatitis B or in virulent chronic hepatitis B, probably indicating active virus replication; there are three subtypes which may exist in a complex with immunoglobulins G.Antibodies, Helminth: Immunoglobulins produced in a response to HELMINTH ANTIGENS.HLA-G Antigens: Class I human histocompatibility (HLA) surface antigens encoded by alleles on locus B of the HLA complex. The HLA-G antigens are considered non-classical class I antigens due to their distinct tissue distribution which differs from HLA-A; HLA-B; and HLA-C antigens. Note that several isoforms of HLA-G antigens result from alternative splicing of messenger RNAs produced from the HLA-G*01 allele.Antigens, CD28: Costimulatory T-LYMPHOCYTE receptors that have specificity for CD80 ANTIGEN and CD86 ANTIGEN. Activation of this receptor results in increased T-cell proliferation, cytokine production and promotion of T-cell survival.Antigens, T-Independent: Antigens which may directly stimulate B lymphocytes without the cooperation of T lymphocytes.Immunodominant Epitopes: Subunits of the antigenic determinant that are most easily recognized by the immune system and thus most influence the specificity of the induced antibody.Herpesvirus 4, Human: The type species of LYMPHOCRYPTOVIRUS, subfamily GAMMAHERPESVIRINAE, infecting B-cells in humans. It is thought to be the causative agent of INFECTIOUS MONONUCLEOSIS and is strongly associated with oral hairy leukoplakia (LEUKOPLAKIA, HAIRY;), BURKITT LYMPHOMA; and other malignancies.ABO Blood-Group System: The major human blood type system which depends on the presence or absence of two antigens A and B. Type O occurs when neither A nor B is present and AB when both are present. A and B are genetic factors that determine the presence of enzymes for the synthesis of certain glycoproteins mainly in the red cell membrane.Hypersensitivity, Delayed: An increased reactivity to specific antigens mediated not by antibodies but by cells.Immunoassay: A technique using antibodies for identifying or quantifying a substance. Usually the substance being studied serves as antigen both in antibody production and in measurement of antibody by the test substance.CA-125 Antigen: Carbohydrate antigen most commonly seen in tumors of the ovary and occasionally seen in breast, kidney, and gastrointestinal tract tumors and normal tissue. CA 125 is clearly tumor-associated but not tumor-specific.Antigens, Nuclear: Immunologically detectable substances found in the CELL NUCLEUS.Cancer Vaccines: Vaccines or candidate vaccines designed to prevent or treat cancer. Vaccines are produced using the patient's own whole tumor cells as the source of antigens, or using tumor-specific antigens, often recombinantly produced.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.Epitope Mapping: Methods used for studying the interactions of antibodies with specific regions of protein antigens. Important applications of epitope mapping are found within the area of immunochemistry.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Hepatitis delta Antigens: Antigens produced by various strains of HEPATITIS D VIRUS.Vaccines, Synthetic: Small synthetic peptides that mimic surface antigens of pathogens and are immunogenic, or vaccines manufactured with the aid of recombinant DNA techniques. The latter vaccines may also be whole viruses whose nucleic acids have been modified.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.Binding Sites, Antibody: Local surface sites on antibodies which react with antigen determinant sites on antigens (EPITOPES.) They are formed from parts of the variable regions of FAB FRAGMENTS.Antigens, CD58: Glycoproteins with a wide distribution on hematopoietic and non-hematopoietic cells and strongly expressed on macrophages. CD58 mediates cell adhesion by binding to CD2; (ANTIGENS, CD2); and this enhances antigen-specific T-cell activation.Gene Frequency: The proportion of one particular in the total of all ALLELES for one genetic locus in a breeding POPULATION.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Antigens, CD1d: A major histocompatibily complex class I-like protein that plays a unique role in the presentation of lipid ANTIGENS to NATURAL KILLER T-CELLS.Bacterial Proteins: Proteins found in any species of bacterium.Prostatic Neoplasms: Tumors or cancer of the PROSTATE.Vaccination: Administration of vaccines to stimulate the host's immune response. This includes any preparation intended for active immunological prophylaxis.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.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.Polysaccharides, Bacterial: Polysaccharides found in bacteria and in capsules thereof.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.