ROLE OF PLATELETS AND COMPLEMENT IN THE CLEARANCE OF EPIMASTIGOTE FORMS OF TRYPANOSOMA-CRUZI

1. Trypanosoma cruzi epimastigote forms are very rapidly removed from the circulation of normal and CS-deficient mice. Depletion of C3 by co bra venom factor results in a significant delay in parasite clearance. 2. During parasite clearance there is a significant decrease in the n umber of circulating platelets and parasite clearance is considerably delayed in thrombocytopenic animals. 3. In vitro incubation of epimast igote forms with normal mouse serum leads to the formation of parasite clumps provided that platelets are present. Inactivation of factor B or depletion of C3 prevents this phenomenon. 4. When epimastigotes are incubated with normal mouse serum they absorb one or more factors req uired for their aggregation with platelets. 5. It is suggested that in mice T. cruzi epimastigote forms are removed from circulation by the alternative pathway of complement activation and that both C3 and plat elets are required for parasite clearance.