title: Immortalized B lymphocytes produce B-cell growth factor.
abstract: The activation, clonal expansion and terminal differentiation of small resting B lymphocytes primed by an antigen (or antibodies to its receptors) appear to follow an orderly developmental sequence triggered at each stage by distinct soluble cytokines, primarily produced by T lymphocytes. For man, the only known B-cell mitogen independent of accessory cells for its action is the Epstein-Barr virus (EBV). Lymphocytes transformed by EBV are released from the usual constraints on B-cell growth, proliferating continuously in the absence of any exogenous cytokine. The resultant cell lines are of special interest as they possess certain features compatible with a preneoplastic state of Burkitt's lymphoma, one of two human cancers with which the virus is intimately associated. We report here that following EBV-transformation, B lymphoblasts release a soluble factor which mimics the B-cell stimulatory product(s) of mitogen-conditioned T lymphocytes. Furthermore, the virally-transformed cells utilize this activity to sustain their own growth. The ectopic production of an otherwise normal growth factor may represent a critical event in the malignant evolution of human lymphomas harbouring the EBV genome.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology*; D002051:Burkitt Lymphoma; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D004261:DNA Replication; D006133:Growth Substances / Q000096:biosynthesis* / Q000276:immunology; D006801:Humans; D015847:Interleukin-4; D007945:Leukemia, Lymphoid; D008222:Lymphokines / Q000096:biosynthesis* / Q000276:immunology; D014066:Palatine Tonsil / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D006133:Growth Substances; D008222:Lymphokines; D015847:Interleukin-4