title: Identification of a novel human B cell activation antigen involved in B cell growth factor-dependent proliferation.
abstract: The B6.4 mAb we present here identifies a novel activation Ag of B cell lineage. The B6.4 mAb was generated by immunizing mice with B cell growth factor (BCGF)-responding BA3 cells, and selected by its capability to block BCGF-induced proliferation of BA3 cells. The inhibitory effect of this antibody on BCGF-dependent proliferation was further confirmed by using normal activated B cells in the presence of exogenous BCGF derived from T cells or B cells. Furthermore, it did not affect IL-2-dependent proliferation of B cells. The expression of the B6.4 Ag, as analyzed by FACS, is restricted to in vitro activated B cells, and remains undetectable on resting B or T cells, PHA-activated T cells, and monocytes. The B6.4 Ag is also expressed on some lymphoblastoid B cell lines and most of the lymphomas and CLL of B cell origin; however, it did not express on pre-B cell ALL and plasma cell leukemias. The B6.4 Ag has a Mr of 35,000 Da, as determined by SDS-PAGE of radiolabeled immunoprecipitates from activated B cells. The B6.4 Ag is detectable on B cells as early as 8 h after activation, and precedes that of the IL-2R or transferrin R. All of these results suggest that the B6.4 Ag is an early activation Ag of B cells and is functionally related to a receptor of BCGF, but not IL-2.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000276:immunology / Q000302:isolation & purification; D001402:B-Lymphocytes / Q000145:classification / Q000166:cytology / Q000276:immunology*; D002460:Cell Line; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000502:physiology; D015847:Interleukin-4; D007378:Interleukins / Q000502:physiology*; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D011233:Precipitin Tests; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000939:Epitopes; D007166:Immunosuppressive Agents; D007378:Interleukins; D015847:Interleukin-4