A role for Lyb-2 in B cell activation mediated by a B cell stimulatory factor.
The Lyb-2 system of the mouse is involved in regulation of a proliferative step in the differentiation of B cells responding to T-dependent antigen. The present study concerns the role of Lyb-2 in an early phase of B cell activation with respect to B cell receptor functions for activation factors. It is shown that interaction of monoclonal anti (alpha)-Lyb-2 antibody with Lyb-2 on the B cell surface induces B cell proliferation by synergistic action with B cell growth factor II-containing factor or interleukin 1. In contrast, alpha-Lyb-2 antibody could not synergize with the Con A-induced culture supernatant of T cell hybridoma FS6-14.13 (FS6) containing B cell stimulatory factor-1 (BSF-1; formerly called BCGF I), and the effect of combining the two was only additive on B cell proliferation. Absorption studies showed that BSF-1 in FS6 could be absorbed by unstimulated B cells, about 95% of which were at Go phase of the cell cycle, but not by thymocytes, and more importantly that alpha-Lyb-2 antibody blocked the absorption in an Lyb-2-specific manner, possibly by competing with BSF-1. It is thus likely that alpha-Lyb-2 antibody may interact with a BSF-1 receptor on B cells or a molecule closely associated with it. Interestingly, alpha-Lyb-2 antibody mimicked the action of BSF-1 in a costimulator assay with affinity-purified goat alpha-mouse IgM antibody, but could not replace all the activities ascribed to BSF-1. Possible mechanisms involved are discussed.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface / Q000502:physiology*; D001402:B-Lymphocytes / Q000276:immunology*; D002453:Cell Cycle; D002454:Cell Differentiation; D006133:Growth Substances / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D015847:Interleukin-4; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000494:pharmacology*; D051379:Mice
D000911:Antibodies, Monoclonal; D000944:Antigens, Differentiation, B-Lymphocyte; D000954:Antigens, Surface; D006133:Growth Substances; D007375:Interleukin-1; D008222:Lymphokines; D015847:Interleukin-4