Trichosanthin, an initiator of the alternative complement activation pathway.

Trichosanthin (TCS), a protein purified from the plant Trichosanthes Kirilowii Maxim, activates normal human serum complement via the alternative pathway, as shown by TCS-induced C3 conversion in normal serum and its prevention by depletion of factor B, but not with the addition of EGTA. Injection of TCS to BALB/c mice consumed the complement alternative pathway (APC) activity in serum, implying in vivo activation of the alternative pathway by TCS. Elevation of peripheral blood leucocyte count as well as protein exudation and neutrophil accumulation in the peritoneal cavities could be induced by peritoneal injection of TCS. The main effect of complement activation by TCS was demonstrated to be induction of neutrophil accumulation.