IDENTIFICATION OF DEFENSIN BINDING TO C1 COMPLEMENT

In human serum we found strong defensin binding to the complexes of ac tivated C1 complement (C (1) over bar) and C1 inhibitor (C1i). Purifie d 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 disso ciated by EDTA, only the activated C1s (C (1) over bar s) bound defens in. Binding of defensins to C (1) over bar complement represents a new ly recognized bridge between the complement- and phagocyte-mediated ho st defenses, and a potential mechanism for protecting infected tissue from cytotoxic injury by defensin.