Evolution of the schistosomal hepatic lesions in mice after curative chemotherapy.

Mice with 64-day-old Schistosoma mansoni infection (+/- 27 worms, 8-12 pairs) were treated simultaneously with oxamniquine and hycanthone. The cure rate was 100%, and changes occurring thereafter in the liver were sequentially followed by means of histologic, ultrastructural, and immunofluorescence methods. Soon after treatment, hepatitic changes cleared up and periovular granulomas diminished in size. The predominant Type III collagen in granulomas was reduced, and the Type I showed no apparent increase, whereas Type IV did not seem to participate in the process. Collagen fibrils in periovular granulomas changed in texture from dense and more oriented to loose and disorganized. Fibroblasts, at first with marked signs of hyperfunction, became less so at a time when collagen fragments appeared within secondary lysosomes in macrophages and fibroblasts. Schistosomal ovular antigens remained sequestered inside the fibrotic granulomas up to the final, 39th day after treatment. Thus, specific treatment of schistosomiasis showed a beneficial effect upon the hepatic lesions from the very beginning and promoted changes in the periovular granulomas that indicated a rapid, although incomplete, resorption of fibrosis.