It was previously found that antiserum to the anti-complementary protein (CoF) in Naja naja venom cross-reacted with a cobra serum protein with many of the characteristics of C3. Cobra serum but not human C3b inactivator destroyed the activity of CoF.
In the present study, the serum and venom of several types of Brazilian snakes were investigated with respect to 1) reactivity with anti-CoF, 2) ability of the venoms to convert human serum C3, 3) ability of the serum to inactivate CoF, and 4) serum alternative pathway activity.
The serum, but not the venoms, of Bothrops jararaca, B. jararacussu, B. moogeni, and Crothalus terrificus contained a protein reactive with anti-CoF but failed to destroy the alternative pathway activity of CoF for human serum. The anti-CoF-reactive serum protein in each of the Brazilian snake serums converted to a more cathodal form on incubation of the serum with Escherichia coli 055:B5 endotoxin (ET), CoF, zymosan (Z), and BSA-rabbit anti-BSA-specific precipitates (AgAb) but not on heating at 52°C for 30 min nor incubation with hydrazine.