title: Anaphylatoxin-mediated regulation of human and murine immune responses.
abstract: C3a and C5a derived from the human complement components C3 and C5, respectively, were found to possess immunoregulatory activities. C3a was found to be capable of suppressing both antigen-specific and polyclonal antibody responses. In contrast, C3a was unable to suppress antigen- or mitogen-induced B or T cell proliferative responses. Helper T cells were found to be the target of C3a-mediated immunosuppression. Suppression occurred via the generation of suppressor T cells. In contrast to the results obtained with C3a, C5a was found to augment both antigen-specific and non-specific in vitro humoral immune responses. Moreover, C5a potentiated antigen- and alloantigen-induced T cell proliferative responses. As opposed to C3ades Arg-77, C5ades Arg retained all of the immunoregulatory activity associated with the intact molecule. Helper T cells are required for C5a-mediated potentiation of the Fc fragment-mediated polyclonal antibody response. Substitution for T cells by a soluble T cell-replacing factor rendered lymphocytes refractory to the enhancing properties of C5a.
mesh_terms: D000706:Anaphylatoxins / Q000276:immunology*; D000818:Animals; D000917:Antibody Formation; D003176:Complement C3 / Q000276:immunology*; D015926:Complement C3a; D003182:Complement C5 / Q000276:immunology*; D015936:Complement C5a; D006801:Humans; D007111:Immunity, Cellular; D007165:Immunosuppression Therapy; D008214:Lymphocytes / Q000276:immunology*; D051379:Mice; D010455:Peptides / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000706:Anaphylatoxins; D003176:Complement C3; D003182:Complement C5; D010455:Peptides; D015926:Complement C3a; D015936:Complement C5a