Kinetics and mechanisms of pulmonary granuloma formation around Schistosoma japonicum eggs injected into mice

Abstract

Granuloma formation in schistosomiasis japonica differs in several respects from those observed in Schistosoma mansoni infections. We have utilized the lung granuloma model in mice sensitized with subcutaneous injection of Schistosoma japonicum eggs to study the kinetics and mechanisms of this response. Animals injected subcutaneously with a range of 50–50,000 S. japonicum eggs elicited a significant pulmonary granulomatous response around ova subsequently injected intravenously. The pulmonary granulomas were formed of macrophages, lymphocytes, and eosinophils. Both antithymocyte globulin and antieosinophil sera reduced significantly the size of the granulomas and depleted the corresponding cell. Nude athymic mice developed markedly reduced pulmonary granulomas as did mice treated with niridazole or hydrocortisone. Sensitization to the egg antigens was demonstrable as both immediate and arthus-type footpad responses. Our data show that cell-mediated pulmonary granulomas can form around S. japonicum eggs in animals previously sensitized by the subcutaneous route. This model may provide further insights into the pathogenesis of S. japonicum granuloma.