INDUCTION OF HEPATIC EGG GRANULOMA HYPORESPONSIVENESS IN MURINE SCHISTOSOMIASIS-MANSONI BY INTRAVENOUS-INJECTION OF SMALL DOSES OF SOLUBLE EGG ANTIGEN

This work was designed to test whether hyporesponsiveness to schistoso mal egg antigen (SEA) was associated with reduction in size of hepatic granulomas. Multiple small doses of SEA (10 mu gx4) were injected int ravenously (i.v.) into C57B1/6 mice either at 7 or 30 days prior to ce rcarial exposure. Eight weeks postinfection, hepatic histopathology an d granuloma diameter were studied. SEA-induced lympho-proliferative re sponse, splenic cytokines (IL-2, IL-4 and IL-5) and serum antischistos omal IgG were assessed. Worm burden and tissue egg load were counted. Compared to infected controls, the SEA-treated groups showed decrease in granuloma diameter, remarkable increase in the percentage of degene rated ova within hepatic granulomas and a:melioration of histopatholog ical changes. SEA lymphoproliferative response, and levels of IL-2 and IL-4, were lower in SEA-treated groups than infected controls. The le vels of IL-5 and antishistosomal IgG were comparable to the infected c ontrols. The intensity of infection was not influenced by i.v. injecti on of SEA. The present data show that i.v. administration of multiple small doses of SEA induced granulomatous hyporesponsiveness with ameli oration of hepatic pathology end acceleration of egg destruction.