The molecular basis of granuloma formation in schistosomiasis. III. In vivo effects of a T cell-derived suppressor effector factor and IL-2 on granuloma formation.

Granuloma formation in schistosomiasis is characterized by the formation of a large lesion in acutely infected animals which subsequently decreases in size as disease progresses into the chronic phase. These in vivo studies confirm and extend previous in vitro observations on the regulation of granulomatous hypersensitivity by a T cell-derived suppressor effector factor (TseF). TseF regulation of granuloma formation in vivo and DTH are shown to be both antigenically and genetically restricted. This suppression is accompanied by a suppression of the ability of cells derived from TseF recipients to function in an in vitro assay of granuloma formation. Antigenic recognition, defined by cellular proliferation in response to antigenic stimulation, is uneffected by TseF administration. Administration of IL-2 reduces TseF function in acutely infected mice and results in increased liver granuloma size. However, the ability of cells derived from these animals to form granulomas in vitro is uneffected. Cells obtained from chronically infected IL-2 recipients do not produce TseF in vitro and granuloma size is increased in these animals. Animals receiving both IL-2 and TseF continue to demonstrate decreased granuloma formation, indicating that IL-2 does not effect the ability of preformed TseF to function. These observations suggest that TseF modulates granuloma formation in vivo and may interact with IL-2 in a dynamic process which determines the intensity of the granulomatous response.