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Leukemia, Hairy Cell: A neoplastic disease of the lymphoreticular cells which is considered to be a rare type of chronic leukemia; it is characterized by an insidious onset, splenomegaly, anemia, granulocytopenia, thrombocytopenia, little or no lymphadenopathy, and the presence of "hairy" or "flagellated" cells in the blood and bone marrow.Leukemia: A progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow. Leukemias were originally termed acute or chronic based on life expectancy but now are classified according to cellular maturity. Acute leukemias consist of predominately immature cells; chronic leukemias are composed of more mature cells. (From The Merck Manual, 2006)Cladribine: An antineoplastic agent used in the treatment of lymphoproliferative diseases including hairy-cell leukemia.Leukemia, Myeloid, Acute: Clonal expansion of myeloid blasts in bone marrow, blood, and other tissue. Myeloid leukemias develop from changes in cells that normally produce NEUTROPHILS; BASOPHILS; EOSINOPHILS; and MONOCYTES.Pentostatin: A potent inhibitor of ADENOSINE DEAMINASE. The drug induces APOPTOSIS of LYMPHOCYTES, and is used in the treatment of many lymphoproliferative malignancies, particularly HAIRY CELL LEUKEMIA. It is also synergistic with some other antineoplastic agents and has immunosuppressive activity.Leukemia, Lymphocytic, Chronic, B-Cell: A chronic leukemia characterized by abnormal B-lymphocytes and often generalized lymphadenopathy. In patients presenting predominately with blood and bone marrow involvement it is called chronic lymphocytic leukemia (CLL); in those predominately with enlarged lymph nodes it is called small lymphocytic lymphoma. These terms represent spectrums of the same disease.Leukemia, Lymphoid: Leukemia associated with HYPERPLASIA of the lymphoid tissues and increased numbers of circulating malignant LYMPHOCYTES and lymphoblasts.Leukemia, B-Cell: A malignant disease of the B-LYMPHOCYTES in the bone marrow and/or blood.Leukemia, Experimental: Leukemia induced experimentally in animals by exposure to leukemogenic agents, such as VIRUSES; RADIATION; or by TRANSPLANTATION of leukemic tissues.Leukemia, Myelogenous, Chronic, BCR-ABL Positive: Clonal hematopoetic disorder caused by an acquired genetic defect in PLURIPOTENT STEM CELLS. It starts in MYELOID CELLS of the bone marrow, invades the blood and then other organs. The condition progresses from a stable, more indolent, chronic phase (LEUKEMIA, MYELOID, CHRONIC PHASE) lasting up to 7 years, to an advanced phase composed of an accelerated phase (LEUKEMIA, MYELOID, ACCELERATED PHASE) and BLAST CRISIS.Leukemia Virus, Murine: Species of GAMMARETROVIRUS, containing many well-defined strains, producing leukemia in mice. Disease is commonly induced by injecting filtrates of propagable tumors into newborn mice.Splenectomy: Surgical procedure involving either partial or entire removal of the spleen.Leukemia, Prolymphocytic: A chronic leukemia characterized by a large number of circulating prolymphocytes. It can arise spontaneously or as a consequence of transformation of CHRONIC LYMPHOCYTIC LEUKEMIA.Interferon Type I: Interferon secreted by leukocytes, fibroblasts, or lymphoblasts in response to viruses or interferon inducers other than mitogens, antigens, or allo-antigens. They include alpha- and beta-interferons (INTERFERON-ALPHA and INTERFERON-BETA).Precursor Cell Lymphoblastic Leukemia-Lymphoma: A neoplasm characterized by abnormalities of the lymphoid cell precursors leading to excessive lymphoblasts in the marrow and other organs. It is the most common cancer in children and accounts for the vast majority of all childhood leukemias.Bone Marrow: The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.Coformycin: A ribonucleoside antibiotic synergist and adenosine deaminase inhibitor isolated from Nocardia interforma and Streptomyces kaniharaensis. It is proposed as an antineoplastic synergist and immunosuppressant.Leukemia, T-Cell: A malignant disease of the T-LYMPHOCYTES in the bone marrow, thymus, and/or blood.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.Leukemia, Monocytic, Acute: An acute myeloid leukemia in which 80% or more of the leukemic cells are of monocytic lineage including monoblasts, promonocytes, and MONOCYTES.Sialic Acid Binding Ig-like Lectin 2: A lectin and cell adhesion molecule found in B-LYMPHOCYTES. It interacts with SIALIC ACIDS and mediates signaling from B-CELL ANTIGEN RECEPTORS.Moloney murine leukemia virus: A strain of Murine leukemia virus (LEUKEMIA VIRUS, MURINE) arising during the propagation of S37 mouse sarcoma, and causing lymphoid leukemia in mice. It also infects rats and newborn hamsters. It is apparently transmitted to embryos in utero and to newborns through mother's milk.Gene Expression Regulation, Leukemic: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in leukemia.Leukemia L1210Remission Induction: Therapeutic act or process that initiates a response to a complete or partial remission level.Lymphoma: A general term for various neoplastic diseases of the lymphoid tissue.Leukemia Virus, Bovine: The type species of DELTARETROVIRUS that causes a form of bovine lymphosarcoma (ENZOOTIC BOVINE LEUKOSIS) or persistent lymphocytosis.Leukemia Virus, Feline: A species of GAMMARETROVIRUS causing leukemia, lymphosarcoma, immune deficiency, or other degenerative diseases in cats. Several cellular oncogenes confer on FeLV the ability to induce sarcomas (see also SARCOMA VIRUSES, FELINE).Antineoplastic Agents: Substances that inhibit or prevent the proliferation of NEOPLASMS.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.Immunophenotyping: Process of classifying cells of the immune system based on structural and functional differences. The process is commonly used to analyze and sort T-lymphocytes into subsets based on CD antigens by the technique of flow cytometry.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Leukemia, Radiation-Induced: Leukemia produced by exposure to IONIZING RADIATION or NON-IONIZING RADIATION.Antigens, CD20: Unglycosylated phosphoproteins expressed only on B-cells. They are regulators of transmembrane Ca2+ conductance and thought to play a role in B-cell activation and proliferation.Myeloid-Lymphoid Leukemia Protein: Myeloid-lymphoid leukemia protein is a transcription factor that maintains high levels of HOMEOTIC GENE expression during development. The GENE for myeloid-lymphoid leukemia protein is commonly disrupted in LEUKEMIA and combines with over 40 partner genes to form FUSION ONCOGENE PROTEINS.Neoplasm, Residual: Remnant of a tumor or cancer after primary, potentially curative therapy. (Dr. Daniel Masys, written communication)Chlorambucil: A nitrogen mustard alkylating agent used as antineoplastic for chronic lymphocytic leukemia, Hodgkin's disease, and others. Although it is less toxic than most other nitrogen mustards, it has been listed as a known carcinogen in the Fourth Annual Report on Carcinogens (NTP 85-002, 1985). (Merck Index, 11th ed)Leukemia P388: An experimental lymphocytic leukemia originally induced in DBA/2 mice by painting with methylcholanthrene.Lymphoproliferative Disorders: Disorders characterized by proliferation of lymphoid tissue, general or unspecified.2-Chloroadenosine: 2-Chloroadenosine. A metabolically stable analog of adenosine which acts as an adenosine receptor agonist. The compound has a potent effect on the peripheral and central nervous system.Deoxyadenosines: Adenosine molecules which can be substituted in any position, but are lacking one hydroxyl group in the ribose part of the molecule.Splenic Neoplasms: Tumors or cancer of the SPLEEN.Leukemia, Biphenotypic, Acute: An acute leukemia exhibiting cell features characteristic of both the myeloid and lymphoid lineages and probably arising from MULTIPOTENT STEM CELLS.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.Bone Marrow Examination: Removal of bone marrow and evaluation of its histologic picture.Neoplasms, Second Primary: Abnormal growths of tissue that follow a previous neoplasm but are not metastases of the latter. The second neoplasm may have the same or different histological type and can occur in the same or different organs as the previous neoplasm but in all cases arises from an independent oncogenic event. The development of the second neoplasm may or may not be related to the treatment for the previous neoplasm since genetic risk or predisposing factors may actually be the cause.Antigens, Differentiation, B-Lymphocyte: Membrane antigens associated with maturation stages of B-lymphocytes, often expressed in tumors of B-cell origin.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.Friend murine leukemia virus: A strain of Murine leukemia virus (LEUKEMIA VIRUS, MURINE) producing leukemia of the reticulum-cell type with massive infiltration of liver, spleen, and bone marrow. It infects DBA/2 and Swiss 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.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.Splenomegaly: Enlargement of the spleen.Interferon-alpha: One of the type I interferons produced by peripheral blood leukocytes or lymphoblastoid cells. In addition to antiviral activity, it activates NATURAL KILLER CELLS and B-LYMPHOCYTES, and down-regulates VASCULAR ENDOTHELIAL GROWTH FACTOR expression through PI-3 KINASE and MAPK KINASES signaling pathways.HL-60 Cells: A promyelocytic cell line derived from a patient with ACUTE PROMYELOCYTIC LEUKEMIA. HL-60 cells lack specific markers for LYMPHOID CELLS but express surface receptors for FC FRAGMENTS and COMPLEMENT SYSTEM PROTEINS. They also exhibit phagocytic activity and responsiveness to chemotactic stimuli. (From Hay et al., American Type Culture Collection, 7th ed, pp127-8)Leukemia-Lymphoma, Adult T-Cell: Aggressive T-Cell malignancy with adult onset, caused by HUMAN T-LYMPHOTROPIC VIRUS 1. It is endemic in Japan, the Caribbean basin, Southeastern United States, Hawaii, and parts of Central and South America and sub-Saharan Africa.Cytarabine: A pyrimidine nucleoside analog that is used mainly in the treatment of leukemia, especially acute non-lymphoblastic leukemia. Cytarabine is an antimetabolite antineoplastic agent that inhibits the synthesis of DNA. Its actions are specific for the S phase of the cell cycle. It also has antiviral and immunosuppressant properties. (From Martindale, The Extra Pharmacopoeia, 30th ed, p472)Acid Phosphatase: An enzyme that catalyzes the conversion of an orthophosphoric monoester and water to an alcohol and orthophosphate. EC 3.1.3.2.Leukemia, Megakaryoblastic, Acute: An acute myeloid leukemia in which 20-30% of the bone marrow or peripheral blood cells are of megakaryocyte lineage. MYELOFIBROSIS or increased bone marrow RETICULIN is common.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.AKR murine leukemia virus: A strain of Murine leukemia virus (LEUKEMIA VIRUS, MURINE) isolated from spontaneous leukemia in AKR strain mice.Lymphoma, B-Cell: A group of heterogeneous lymphoid tumors generally expressing one or more B-cell antigens or representing malignant transformations of B-lymphocytes.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.Fusion Proteins, bcr-abl: Translation products of a fusion gene derived from CHROMOSOMAL TRANSLOCATION of C-ABL GENES to the genetic locus of the breakpoint cluster region gene on chromosome 22. Several different variants of the bcr-abl fusion proteins occur depending upon the precise location of the chromosomal breakpoint. These variants can be associated with distinct subtypes of leukemias such as PRECURSOR CELL LYMPHOBLASTIC LEUKEMIA-LYMPHOMA; LEUKEMIA, MYELOGENOUS, CHRONIC, BCR-ABL POSITIVE; and NEUTROPHILIC LEUKEMIA, CHRONIC.Immunotoxins: Semisynthetic conjugates of various toxic molecules, including RADIOACTIVE ISOTOPES and bacterial or plant toxins, with specific immune substances such as IMMUNOGLOBULINS; MONOCLONAL ANTIBODIES; and ANTIGENS. The antitumor or antiviral immune substance carries the toxin to the tumor or infected cell where the toxin exerts its poisonous effect.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.Leukemia, Myeloid, Chronic-Phase: The initial phase of chronic myeloid leukemia consisting of an relatively indolent period lasting from 4 to 7 years. Patients range from asymptomatic to those exhibiting ANEMIA; SPLENOMEGALY; and increased cell turnover. There are 5% or fewer blast cells in the blood and bone marrow in this phase.Neoplasm Proteins: Proteins whose abnormal expression (gain or loss) are associated with the development, growth, or progression of NEOPLASMS. Some neoplasm proteins are tumor antigens (ANTIGENS, NEOPLASM), i.e. they induce an immune reaction to their tumor. Many neoplasm proteins have been characterized and are used as tumor markers (BIOMARKERS, TUMOR) when they are detectable in cells and body fluids as monitors for the presence or growth of tumors. Abnormal expression of ONCOGENE PROTEINS is involved in neoplastic transformation, whereas the loss of expression of TUMOR SUPPRESSOR PROTEINS is involved with the loss of growth control and progression of the neoplasm.Ribonucleosides: Nucleosides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)Acute Disease: Disease having a short and relatively severe course.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.Precursor B-Cell Lymphoblastic Leukemia-Lymphoma: A leukemia/lymphoma found predominately in children and adolescents and characterized by a high number of lymphoblasts and solid tumor lesions. Frequent sites involve LYMPH NODES, skin, and bones. It most commonly presents as leukemia.Blood Cell Count: The number of LEUKOCYTES and ERYTHROCYTES per unit volume in a sample of venous BLOOD. A complete blood count (CBC) also includes measurement of the HEMOGLOBIN; HEMATOCRIT; and ERYTHROCYTE INDICES.Recurrence: The return of a sign, symptom, or disease after a remission.Interleukin-3 Receptor alpha Subunit: A low affinity interleukin-3 receptor subunit that combines with the CYTOKINE RECEPTOR COMMON BETA SUBUNIT to form a high affinity receptor for INTERLEUKIN-3.Neoplastic Stem Cells: Highly proliferative, self-renewing, and colony-forming stem cells which give rise to NEOPLASMS.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.Lymphoma, Non-Hodgkin: Any of a group of malignant tumors of lymphoid tissue that differ from HODGKIN DISEASE, being more heterogeneous with respect to malignant cell lineage, clinical course, prognosis, and therapy. The only common feature among these tumors is the absence of giant REED-STERNBERG CELLS, a characteristic of Hodgkin's disease.Spleen: An encapsulated lymphatic organ through which venous blood filters.Deltaretrovirus: A genus in the family RETROVIRIDAE consisting of exogenous horizontally-transmitted viruses found in a few groups of mammals. Infections caused by these viruses include human B- or adult T-cell leukemia/lymphoma (LEUKEMIA-LYMPHOMA, T-CELL, ACUTE, HTLV-I-ASSOCIATED), and bovine leukemia (ENZOOTIC BOVINE LEUKOSIS). The type species is LEUKEMIA VIRUS, BOVINE.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.