Complement and Feline Leukemia

Our interest in complement and leukemia has emerged from studies by Kassel et al. (J. Exp. Med., 138:925, 1973) and Hardy et al. (unpublished results) that infusion of normal plasma in mice, cats, and dogs causes massive dstruction of leukemic cells. Evidence in the mouse indicates that the anti-leukemic factor is a component of the complement system, C5. We have therefore begun to assay C and C component levels in cat serum. With functionally pure C1 and C2 and intermediate cells (EAC1, EAC4, EAC1,4) prepared from cat serum, the measurement of C1, C4 and C2 can be accomplished when the source of terminal C components, C3 to C9 is guinea pig serum in EDTA. With cat serum in EDTA, lysis does not occur. The blocking effect appears to be due to a potent inhibitor present in cat serum. This inhibitor is anti-complementary to guinea pig and human serum.