Identification of defensin binding to C1 complement

Abstract
In human serum we found strong defensin binding to the complexes of activated C1 complement (C ) and C1 inhibitor (C1i). Purified C1q, activated C1 tetramer ( 2 2) and C1i did not bind defensin. When ( 2 2) was dissociated by EDTA, only the activated C1s (C s) bound defensin. Binding of defensins to C complement represents a newly recognized bridge between the complement- and phagocyte-mediated host defenses, and a potential mechanism for protecting infected tissue from cytotoxic injury by defensin.