UNIMPAIRED DOWN-MODULATION OF THE HEPATIC GRANULOMATOUS RESPONSE IN CD8 T-CELL-DEFICIENT AND GAMMA-INTERFERON-DEFICIENT MICE CHRONICALLY INFECTED WITH SCHISTOSOMA-MANSONI

The granulomatous response to schistosome eggs is a CD4 T-cell-depende nt, Th2-cytokine-dominated immunopathologic response. As infection pro ceeds to chronicity, both granuloma formation and egg-induced cytokine production become domnregulated, and previous experiments have implic ated CD8 T cells in this process. One mechanism by which CD8 T cells c ould suppress immunopathology is through the production of the counter regulatory cytokine gamma interferon (IFN-gamma), but no in vivo evide nce exists to directly support this hypothesis. In this study, we anal yzed hepatic granuloma formation and egg-induced cytokine production i n Schistosoma mansoni-infected gene knockout mice deficient in either CD8 lymphocytes or IFN-gamma. Surprisingly, we found that neither immu nologic component plays an essential function in the control of granul oma and cytokine responses during either the acute or chronic stage of infection. Thus, other mechanisms may be more important in the regula tion of immunopathology in schistosomiasis.