Cutting edge: recruitment of the CD19/CD21 coreceptor to B cell antigen receptor is required for antigen-mediated expression of Bcl-2 by resting and cycling hen egg lysozyme transgenic B cells.
Recruitment of the CD19/CD21 coreceptor is thought to lower the threshold for effective signaling through the B cell Ag receptor. We provide evidence supporting a second role for coreceptor recruitment, and that is to enhance the survival/proliferative potential of the responding B cells. We show that B cell Ag receptor signaling in the absence of coreceptor recruitment induces cellular accumulation of the anti-apoptotic protein Bcl-xL, whereas CD19-mediated signals are required for Bcl-2 accumulation. The expression of both anti-apoptotic proteins correlates with the enhanced responsiveness of both resting and cycling B cells to growth-promoting signals delivered through CD40. These results provide further evidence for the necessity of coreceptor recruitment during Ag-dependent B cell activation and indicate that Ags derived from inflammatory sites function as better thymus-dependent Ags than their counterparts not coated with complement fragments.
Roberts
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Department of Microbiology and Immunology, University of Kentucky Medical Center, Lexington 40536, USA.
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D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000502:physiology; D018941:Antigens, CD19 / Q000378:metabolism* / Q000502:physiology; D016175:B-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D005260:Female; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D007399:Interphase / Q000235:genetics / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009113:Muramidase / Q000235:genetics* / Q000276:immunology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D011940:Receptor Aggregation / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism* / Q000502:physiology; D017464:Receptors, Complement 3d / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000276:immunology; D019076:Transgenes / Q000276:immunology*
D000888:Antibodies, Anti-Idiotypic; D018941:Antigens, CD19; D007148:Immunoglobulin mu-Chains; D019253:Proto-Oncogene Proteins c-bcl-2; D011947:Receptors, Antigen, B-Cell; D017464:Receptors, Complement 3d; D009113:Muramidase