Relative imbalance between T regulatory cells and activated T cells in mice with differential morbidity in chronic Schistosoma mansoni infections.

Chronic (20-week) Schistosoma mansoni infections of CBA/J male mice present as two distinct forms of morbidity. Most mice develop moderate splenomegaly syndrome (MSS) resembling the intestinal form of chronic human schistosomiasis mansoni, while approximately 20% of mice develop hypersplenomegaly syndrome (HSS), more consistent with the severe hepatosplenic form of chronic human schistosomiasis mansoni. Here, we report the relative proportions of natural T regulatory cells (Treg) and activated CD4(+) T cells (Tact) for both splenic and granulomatous cell populations of MSS and HSS mice. Proportions of both Treg and Tact are greater in HSS than MSS mice. However, the ratios of Treg to Tact in both splenic and granulomatous cell populations from MSS mice are significantly higher than those of HSS mice. For both HSS and MSS mice, in vitro proliferation of their CD3(+) splenic cells induced by soluble egg antigens is inversely correlated with the ratio of Treg to Tact. Also, spleen or granuloma cells from MSS mice produced higher mean levels of IFN-gamma than those from HSS mice. Differential IFN-gamma productive capacities dictated by Treg : Tact ratios may contribute to the development of differential morbidities in this model of chronic experimental schistosomiasis mansoni.