In murine schistosomiasis mansoni, granulomatous inflammation is an immune response that involves egg antigen presentation to T cells in the context of class II major histocompatibility complex determinants and subsequent inflammatory lymphokine production by delayed-hypersensitivity (TDH) lymphocytes. In the present study, monoclonal antibodies directed against L3T4, I-A, and Lyt-2 molecules were injected intraperitoneally into S. mansoni-infected mice to study the role of these membrane antigens in the process of granuloma formation. A dramatic suppression of the hepatic granuloma size and antigen-induced interleukin-2 (IL-2) production by spleen cells was seen in mice that received anti-L3T4 monoclonal antibody treatment. The total number of cells, especially the L3T4+ T cells, was greatly diminished in the spleens. Furthermore, histopathological study of the granulomas in stained liver sections demonstrated the paucity of eosinophils and macrophages, absence of epithelioid cells and multinucleated giant cells, and minimal collagen deposition within the lesions. Damaged hepatocytes were also seen surrounding these il-formed granulomas. In contrast, anti-I-A monoclonal antibody treatment partially suppressed IL-2 production, although granuloma size and cellular composition remained the same. Mice that received anti-Lyt-2 monoclonal antibody did not show any changes in either IL-2 production or hepatic granulomatous inflammation. The data presented in this paper indicate a crucial role for L3T4 molecules present on a subset of class II major histocompatibility complex-restricted TDH cells in IL-2 production and the generation of the granulomatous response.

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