IDENTIFICATION OF DEFENSIN BINDING TO C1 COMPLEMENT

In human serum we found strong defensin binding to the complexes of activated C1 complement (C (1) over bar) and C1 inhibitor (C1i). Purified C1q, activated C1 tetramer ((r) over bar(2) (s) over bar(2)) and C1i did not bind defensin. When (r) over bar(2) (s) over bar(2) was dissociated by EDTA, only the activated C1s (C (1) over bar s) bound defensin. Binding of defensins to C (1) over bar 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.