The Schistosoma mansoni egg granuloma: quantitation of cell populations.

Granulomas were induced by the intravenous injection of eggs of Schistosoma mansoni into the lungs of mice which were either unsensitised, sensitised by prior intraperitoneal injection of eggs, or naturally infected with S. mansoni. At various time intervals after egg injection (8, 16 and 32 days in unsensitised mice; 4, 8 and 16 days in sensitised mice; and 8 days in mice infected for 4, 8 16 and 24 wk) the lungs were removed from groups of mice and were placed in a Waring blender at low speed. Complete intact granulomas were isolated, the lesions were dispersed with collagenase and pronase and the cell populations quantified and classified as eosinophils, neutrophils and mononuclear cells less than or equal to 12 or greater than 12 micron in diameter. Small mononuclear cells consisting almost exclusively of lymphocytes were the predominant cells initially, but eosinophils became the most common cell type, reaching a peak of 71% of cells in sensitised animals 16 days after injection. Large mononuclear cells remained relatively constant at about 30% of the total cells. Neutrophils neverreached more than 10% of cells. Sensitisation by a prior intraperitoneal injection of eggs led to an acceleration of granuloma formation. In infected mice, the granulomas with the largest cell counts were seen 8 wk after infection while the smaller granulomas in the mice infected for 16 or 24 wk confirm the previously reported modulation of this immunopathological reaction.