An ultrastructural study of hepatic granulomas and schistosome egg shells in murine hepatosplenic schistosomiasis mansoni

At 8, 11, 33, and 52 weeks after exposure to cereariae of Schistosoma mansoni, mice with overt hepatosplenic disease were sacrificed and their livers were taken for light and electron microscopic study. Hepatic granulomas were encountered at all intervals. The three major cellular components (eosinophils, fibroblasts, and macrophages) were intermingled without apparent order and were interspersed with the more sparse cellular elements (neutrophils, lymphocytes, and plasma cells). Both eosinophils and fibroblasts displayed phagosomes, but never in the large numbers observed in macrophage derivatives. In addition to abundant phagosomes, these cells (the epithelioid and multinueleated giant cells) were characterized by a well-developed rough endoplasmic reticulum, many free cytoplasmic ribosomes, and plasma membranes that were focally thrown into numerous slender tentacles which interdigitated extensively and formed elaborate imbricated or spiraled configurations. While the macrophage derivatives seemed to function prineipally by phagocytosis, they also appeared eapable of extracellular digestion, since schistosome egg shells disintegrated in proximity to intact epithelioid or multinueleated giant cells. Intact schistosome egg shells appeared fenestrated and displayed on their outer aspeets unmerous microspicules that projected toward and frequently contacted the encompassing inflammatory elements. It was suggested that the shell fenestrations might facilitate diffusion of antigenic materials from the schistosome eggs to the surrounding granuloma phagocytes, and that the shell microspicules might function as mechanical irritants to contiguous cells.