Inability of the C3a anaphylatoxin to promote cellular lysis

Investigation of the biological effects of the cleavage product, C3a, derived from the third component of complement has generally focused on the effects it exerts as an anaphylatoxin, that is, smooth muscle contraction and histamine release from mast cells and basophils. Therefore, reports that C3a exerts cytoxic effects on various cell types, and exhibits concentration-dependent specificity for malignant cells, excited great interest. The cytolytic activity mediated by macrophages which were activated in vitro may be attributed to their ability to generate C3a. The far-reaching implications of such a cytolytic role for C3a led us to pursue these observations further. We report here that we have been unable to duplicate the results reported by Ferluga et al. On the contrary, we find that C3a actually reduces spontaneous release of label below normal background levels.