RESUMO
To investigate the immunomodulatory effect of the Th1 mediated cytokine IFN-alpha on schistosomiasis, this cytokine was weekly injected into mice experimentally infected with S. mansoni, beginning from day 0 [group II], week 3 [group III], week 6 [group IV] and week 10 [group V] post-infection. TGF beta 1 serum levels were estimated on a weekly basis and beginning one week after initiation of IFN-alpha therapy, while all animals were sacrified on week 14 to be used for egg counts in liver and small intestine, oogram study for determination of the maturity of deposited eggs, and histopathological examination of stained liver sections. IFN-alpha treated groups were characterized by a more intense oviposition in the intestine [liver/intestine ratio less than 1], with higher egg numbers the earlier IFN-alpha was administered. Oograms of the intestine indicated the level of immature eggs to be statistically significantly higher in group II, III and IV than in the control group I [p < 0.05]. In IFN-alpha medicated mice, the mean numbers and diameters of hepatic granulomas were less than in GI, in addition to a lower representation of fibrocellular and fibrous granulomas among them [all parameters p < 0.05], especially in Gs IV and V. The inflammatory cell population in the form of eosinophils, histiocytes and giant cells was more pronounced in Gs III, IV and V. TGF-beta 1 serum levels showed a progressive rise, however more pronounced in the untreated control. A statistically positive significant was established between TGF-beta 1 levels and number, size and percentage of fibrotic hepatic granulomas in all groups