Delayed hypersensitivity granuloma formation around Schistosoma mansoni eggs in vitro. I. Definition of the model

An in vitro model of granuloma formation was established in order to study the cellular interactions involved in the formation of delayed hypersensitivity granulomas and the cellular interactions responsible for host modulation of that response in chronic infections of schistosomiasis. This model utilizes Schistosoma mansoni eggs from adult worm pairs that have been cultured in vitro as an antigenic source and spleen cells from either normal or actively infected C57BL/6 mice as the cell donors. The results establish a consistent sequence of events characterized by initial adherence of mononuclear cells to the egg; subsequent blast transformation by these cells; recruitment of additional mononuclear cell populations, including lymphocytes and macrophages; and recruitment of eosinophils and fibroblasts, which are capable of synthesizing collagen. The immunologic nature of this reaction has been established through analyses after presensitization either by natural infection or through the use of soluble egg antigen. These studies have demonstrated the immunologic specificity of the reaction, its dependence on an initial T lymphocyte-mediated event, and recruitment of other cell populations. Preliminary studies show that modulation in vitro reflects the in vivo kinetics of granuloma modulation.