title: The complement system and adaptive immunity.
abstract: The complement system covalently attaches C3d to microbial antigens which binds to CR2 on B lymphocytes, leading to a markedly enhanced adaptive immune response to that antigen. The enhancement is mediated by the cross-linking of the CR2-CD19 complex to mIg which augments the activation of several intracellular signalling pathways. Two additional receptors of the B lymphocyte, FcgammaRIIB and CD22, have opposing effects when cross-linked to mIg, the former suppressing signalling by recruiting the inositol phosphatase, SHIP, and the latter by activating the phosphotyrosine phosphatase, SHP-1. Two principles emerge from these studies: innate immunity guides the adaptive immune response, and activation of the B lymphocyte is determined by co-receptors which evaluate the biological characteristics of antigen.
authors.affiliation: Wellcome Trust Immunology Unit, University of Cambridge School of Clinical Medicine, Hills Road, Cambridge, CB2 2SP, UK.
authors.forename: D T
authors.initials: DT
authors.lastname: Fearon
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000502:physiology; D018941:Antigens, CD19 / Q000502:physiology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology; D015815:Cell Adhesion Molecules; D003176:Complement C3 / Q000502:physiology; D003165:Complement System Proteins / Q000502:physiology*; D006801:Humans; D007109:Immunity; D037102:Lectins; D008213:Lymphocyte Activation; D017464:Receptors, Complement 3d / Q000502:physiology; D017452:Receptors, IgG / Q000502:physiology; D051918:Sialic Acid Binding Ig-like Lectin 2
chemical_list: D015703:Antigens, CD; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; D015815:Cell Adhesion Molecules; D003176:Complement C3; D037102:Lectins; D017464:Receptors, Complement 3d; D017452:Receptors, IgG; D051918:Sialic Acid Binding Ig-like Lectin 2; D003165:Complement System Proteins