Structure and function of chemotactic factor, C5a, and its receptor

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C5a is a potent chemotactic peptide derived from complement C5. C5a is immediately inactivated to C5a des Arg by carboxypeptidase N after activation of complement. Physiological C5a action occur through C5a receptor on phagocytic cells. In this study, we determined epitopes on C5a to understand the role of C5a using series of anti C5a monoclonal antibodies and N-terminal or C-terminal oligopeptides from C5a. Bindings between C5a des Arg and anti C5a monoclonal antibody were not inhibited by either N-terminal or C-terminal oligopeptides. However C-terminal oligopeptides without Arg could inhibit binding between C5a des Arg and some anti C5a monoclonal antibodies. These results demonstrate that some anti C5a monoclonal antibodies can recognize C-terminal peptide only without Arg.