Commercial cobra factor is prepared from the venom of either Naja naja, the Indian cobra, or Naja haje, the Egyptian cobra, and is not marked as to source. Cobra factor from Naja haje (CVFh), although able to generate C3-cleaving activity, does not support passive lysis. Cobra venom from Naja naja (CVFn), upon incubation with normal human serum, depletes C3 through C9, and causes conversion of C3 and B as observed in immunoelectrophoresis. CVFh also causes conversion of C3 and B and depletes C3; but C5 through C9 are spared. CVFh and CVFn were found to be equally resistant to C3bINAhu.

When CVFn was incubated with normal human or guinea pig serum, an activity was generated which was detectable as a zone of hemolysis in agarose plates containing guinea pig erythrocytes and EDTA, when placed near a well containing human or rat, but not guinea pig, CEDTA.

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