Complement inhibitor(s) released by leukocytes. I. Pretreatment of sheep erythrocytes with supernatants of mouse spleen and thymus cells inhibit whole complement activity and C2 utilization

Sheep erythrocytes pretreated with supernatants of mouse spleen or thymus cells become resistant to lysis by guinea pig complement. The inhibitory activity (IA) reduces the utilization of C2 by EAC14. Because IA binds to the surface of sheep erythrocytes and does not inhibit C1 irreversibly, it is probably a hitherto undescribed inhibitor of complement.