title: Regulation of humoral immunity by complement.
abstract: The complement system of innate immunity is important in regulating humoral immunity largely through the complement receptor CR2, which forms a coreceptor on B cells during antigen-induced activation. However, CR2 also retains antigens on follicular dendritic cells (FDCs). Display of antigen on FDCs is critical for clonal selection and affinity maturation of activated B cells. This review will discuss the role of complement in adaptive immunity in general with a focus on the interplay between CR2-associated antigen on B cells with CR2 expressed on FDCs. This latter interaction provides an opportunity for memory B cells to sample antigen over prolonged periods. The cocrystal structure of CR2 with its ligand C3d provides insight into how the complement system regulates access of antigen by B cells with implications for therapeutic manipulations to modulate aberrant B cell responses in the case of autoimmunity.
authors.affiliation: Immune Disease Institute and Program in Molecular and Cellular Medicine, Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, 02115 MA, USA. carroll@idi.harvard.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Carroll
authors.forename: David E
authors.initials: DE
authors.lastname: Isenman
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D000941:Antigens / Q000276:immunology; D018941:Antigens, CD19 / Q000276:immunology; D015551:Autoimmunity / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D003167:Complement Activation / Q000276:immunology; D015933:Complement C3d / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D020566:Dendritic Cells, Follicular / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D056724:Immunity, Humoral / Q000276:immunology*; D007113:Immunity, Innate; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D018345:Mice, Knockout; D017464:Receptors, Complement 3d / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D060225:Tetraspanin 28 / Q000276:immunology
chemical_list: D000941:Antigens; D018941:Antigens, CD19; D017464:Receptors, Complement 3d; D060225:Tetraspanin 28; D015933:Complement C3d