MICE LACKING THE GAMMA-INTERFERON RECEPTOR HAVE AN IMPAIRED GRANULOMATOUS REACTION TO SCHISTOSOMA-MANSONI INFECTION

The egg-induced granulomatous reaction in Schistosoma mansoni-infected individuals develops within the portal system of the liver and is the major pathological finding in schistosomiasis. We have infected mice lacking the gamma interferon (IFN-gamma) receptor with S. mansoni larv ae and studied the development of hepatic granulomas in these mutant m ice in comparison to that in control wild-type mice. In the absence of IFN-gamma activity, a dramatic reduction in the size and architecture of the granuloma was observed. Granulomas from mutant mice were small er than those from the control group and showed a significant reductio n in the number of infiltrating inflammatory cells. Moreover, they app ear to prematurely progress to the chronic phase of the reaction at a time when the control group still has acute inflammation. Our data sug gests a pivotal role for IFN-gamma in the early events of the granulom atous reaction in vivo.