Phagocytosis: A Defense Mechanism against Infection with Trypanosoma Cruzi

Abstract

In mice, depression of reticuloendothelial activity by intravenous injection of silica particles resulted in a decreased resistance to infection with virulent blood forms (trypomastigotes) of Trypanosoma cruzi. In these animals, both the mortality rate and the levels of parasitemia were significantly increased over those of control mice given only the parasites. Accordingly, stimulation of the reticuloendothelial system (RES) with diethylstilbestrol (DES) before infection reduced considerably both the mortality rate and the levels of parasitemia, and prolonged the survival time after infection. Although in low percentages (16 to 25%), survival after the 60-day observation period was observed only among mice which had been treated with DES. Virulent trypomastigote forms of T. cruzi were found inside mouse peritoneal macrophages shortly after intraperitoneal (i.p.) injection. Many of the parasites were killed within these cells both in vivo and in vitro. The data reported in this paper indicate that, in the mouse, the RES is involved in the resistance against infection with virulent blood forms of T. cruzi, possibly through the capacity of macrophages to destroy the parasite.