Complement's participation in acquired immunity.
The preliminary evidence for the involvement of complement in promoting primary humoral responses dates back over a quarter of a century. However, it is only in the course of the past decade or so that the detailed mechanisms underlying complement's influence have been characterized in depth. It is now clear that complement serves as a regulator of several B cell functions, including specific antibody production, antigen uptake, processing and presentation, and shaping of the B cell repertoire. Of key importance, in this respect, is the role played by the B cell-signaling triad consisting of the B cell receptor for antigen (BCR), a complex composed of the iC3b/C3d fragment-binding complement type 2 receptor (CR2, CD21) and its signaling element CD19 and the IgG-binding receptor FcgammaRIIb (CD32). The positive or negative outcome of signaling through this triad is determined by the context in which antigen is seen, be it alone or in association with natural or induced antibodies and/or C3-complement fragments. The aim of this review is to describe the present status of our understanding of complement's participation in acquired immunity and the regulation of autoimmune responses.
Nielsen
Claus Henrik
CH
Institute for Inflammation Research, Rigshospitalet, University Hospital Copenhagen, Denmark.
Leslie
Robert Graham Quinton
RG
D000818:Animals; D000917:Antibody Formation; D017951:Antigen Presentation / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology; D018941:Antigens, CD19 / Q000276:immunology; D015551:Autoimmunity / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D003167:Complement Activation; D003179:Complement C3b / Q000276:immunology; D003181:Complement C4 / Q000276:immunology; D015938:Complement Membrane Attack Complex / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology; D006168:Guinea Pigs; D006801:Humans; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D021962:Membrane Microdomains / Q000502:physiology; D051379:Mice; D011947:Receptors, Antigen, B-Cell / Q000276:immunology; D017464:Receptors, Complement 3d / Q000276:immunology; D015398:Signal Transduction
D000942:Antigens, Bacterial; D018941:Antigens, CD19; D003181:Complement C4; D015938:Complement Membrane Attack Complex; D046911:Macromolecular Substances; D011947:Receptors, Antigen, B-Cell; D017464:Receptors, Complement 3d; D003179:Complement C3b; D003165:Complement System Proteins