title: B7, a B-cell-restricted antigen that identifies preactivated B cells.
abstract: After activation with antigen or mitogen, a number of cell surface proteins appear that are not expressed on resting B cells. To date, a number of B lineage restricted and associated activation antigens have been reported that appear at distinct intervals after in vitro activation. In this report, we describe a new B lineage restricted activation antigen (B7) that appears within 24 hr of in vitro stimulation. The expression of B7 antigen, which is detected on a minor subpopulation of B cells isolated from peripheral blood and lymphoid tissues, is strongly induced following stimulation with either anti-immunoglobulin or Epstein-Barr virus. In contrast, B7 was not detected on resting or activated T cells or monocytes. The B7 antigen was expressed on a subset of B cell lines and B cell neoplasms, but was not detected on leukemias and lymphomas of T cell or myeloid origin. B7 was distinguished from other B cell restricted and associated activation antigens by its unique pattern of expression on a variety of hemopoietic cell lines. The biochemical characterization of B7, that it is a single chain protein of 60 kDa, further distinguishes it from other B cell activation antigens. The functional importance of the B7 antigen was demonstrated when splenic B cells were fractionated into the B7+ and B7- populations. The peak of proliferation in response to anti-Ig, appeared earlier within the B7+ population. These studies suggest that B7 antigen identifies a subpopulation of B cells that are preactivated or primed in vivo, and have an accelerated response to subsequent activation via cross-linking of surface Ig.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000276:immunology; D000951:Antigens, Neoplasm / Q000032:analysis; D001402:B-Lymphocytes / Q000032:analysis / Q000145:classification* / Q000166:cytology; D002454:Cell Differentiation; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000166:cytology; D014407:Tumor Cells, Cultured / Q000032:analysis
chemical_list: D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm