Modulation of the immune response by plasma protease inhibitors III. Alpha 1-antichymotrypsin inhibits human natural killing and antibody-dependent cell-mediated cytotoxicity.

The effects of alpha 1-antichymotrypsin (AChy), a serum protease inhibitor, on two parameters of the cellular immune response, natural killing (NK) and antibody-dependent cell-mediated cytotoxicity (ADCC), were tested. Both NK and ADCC were inhibited by the protein in a dose-dependent fashion. Our results suggest that this protease inhibitor binds to the surface of NK and ADCC target cells and neutralizes the lytic signal passed between the effector and target.