A novel mechanism for complement activation at the surface of B cells following antigen binding.
Coligation of CD21 with BCR on the surface of B cells provides a costimulatory signal essential for efficient Ab responses to T-dependent Ags. To achieve this, Ag must be directly linked to C3 fragments, but how this occurs in vivo is not fully understood. Using BCR transgenic mice, we demonstrated that C3 was deposited on the surface of B cells following both high- and moderate-affinity Ag binding. This was dependent on the specific binding of IgM to the BCR-bound Ag and can occur independently of soluble immune complex formation. Based on these data, we propose a novel model in which immune complexes can form directly on the surface of the B cell following Ag binding. This model has implications for our understanding of B lymphocyte activation.
Manderson
Anthony P
AP
Cancer and Vascular Biology Group, Division of Immunology and Genetics, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
Quah
Ben
B
Botto
Marina
M
Goodnow
Chris C
CC
Walport
Mark J
MJ
Parish
Chris R
CR
D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology*; D000941:Antigens / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology* / Q000502:physiology; D003167:Complement Activation / Q000276:immunology*; D003176:Complement C3 / Q000378:metabolism; D007075:Immunoglobulin M / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D011947:Receptors, Antigen, B-Cell / Q000276:immunology
D000936:Antigen-Antibody Complex; D000941:Antigens; D003176:Complement C3; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell