title: Suppression of humoral immune responses by synthetic C3a peptides.
abstract: Synthetic oligopeptides based on the COOH-terminal sequence of native human C3a were examined for the ability to suppress antigen-specific and polyclonal antibody responses. The synthetic peptides were found to qualitatively mimic the suppressive actions of human C3a, but proved to be less active on a molar basis. Comparison of the activity of the peptides with native C3a indicates that the most potent peptide is C3a 57-77 with C3a 65-77, C3a 70-77, C3a[Ala 71,72]70-77, and C3a 73-77 being less active, respectively. These results indicate that the region of the C3a molecule responsible for immunosuppression is located in the COOH region.
mesh_terms: D000706:Anaphylatoxins / Q000494:pharmacology*; D000818:Animals; D000917:Antibody Formation; D000921:Antibody-Producing Cells / Q000276:immunology; D003176:Complement C3 / Q000031:analogs & derivatives / Q000502:physiology*; D015926:Complement C3a; D006462:Hemolytic Plaque Technique; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*
chemical_list: D000706:Anaphylatoxins; D003176:Complement C3; D007166:Immunosuppressive Agents; D009842:Oligopeptides; D010455:Peptides; D015926:Complement C3a