Heterogeneity of the granulomatous response in the liver, colon, ileum, and ileal Peyer's patches to schistosome eggs in murine schistosomiasis mansoni.

Abstract

Murine schistosomiasis mansoni is a parasitic disease in which granulomas form around schistosome eggs in the liver and intestines. In the present study, we compared the size of the granulomatous lesions in various organs during both the acute and chronic phase of infection.With chronic infection, there was a spontaneous decrease in the size of the granulomatous response to newly generated schistosome eggs (modulation) in the liver, colon, and ileal Peyer’s patches. Modulation occurred earlier during the course of infection in the colon and Peyer’s patches compared with the liver. Granulomas in the ileum were smaller than granulomas in other organs and did not modulate with chronic infection.Cyclophosphamide or Cimetidine treatment of acutely infected mice increased granuloma size in the liver, colon, and Peyer’s patches without affecting granuloma size in the ileum.Transfer of spleen cells from chronically infected mice into animals with acute infections resulted in decreased granuloma size in the liver, colon, and ileal Peyer’s patches without affecting ileal granuloma size. Granulomas in the colon and Peyer’s patches were maximally suppressed by as few as 1 × 107 spleen cells, whereas 4 × 107 cells were required to induce a similar response in the liver. Suppression was abolished by prior treatment of spleen cells with anti-Thy 1.2 and complement.We conclude that 1) natural modulation of the granulomatous response occurs in the liver, colon, and ileal Peyer’s patches; 2) granulomas in the liver, colon, and ileal Peyer’s patches of both acute and chronically infected mice are partially under suppressor T lymphocyte regulation; 3) granulomas in the ileal mucosa are markedly suppressed throughout the course of infection by a mechanism that does not involve a cyclophosphamide or Cimetidine sensitive lymphocyte; and 4) early modulation of colon and Peyer’s patch granulomas during the course of infection may be related to selective homing of/or increased sensitivity to suppressor cells.