Granuloma formation is an essential host response to many intracellular pathogens and some particulate antigens. T lymphocytes, especially CD4+ T-cells, are required for the initial formation and ongoing maintenance of the inflammatory response. In the absence of CD4+ T-cells, most infections which normally provoke a granulomatous response are more widely disseminated or lethal since the protective lesions are either malformed or absent. The role of T-cell receptor mediated antigen specificity in infectious states is reviewed with a special emphasis upon recent work on S. mansoni induced granulomas.