Alteration of granuloma angiotensin I-converting enzyme activity by regulatory T lymphocytes in murine schistosomiasis.

Granulomatous inflammatory lesions in murine schistosomiasis mansoni undergo a spontaneous diminution at the chronic phase of the disease concurrent with an increase in angiotensin I-converting enzyme (ACE) activity. The objective of this investigation was to determine whether T cells influence ACE activity within the granulomas. Cyclophosphamide and cimetidine treatments of mice, which augment delayed-type hypersensitivity reactions, enhanced liver granuloma size and decreased granuloma ACE activity. The suppression of liver granuloma by the adoptive transfer of spleen cells from chronically infected, immunomodulated mice into recipients with acute infection increased ACE activity of granulomas and granuloma macrophages. The increased ACE activity was dependent upon the transfer of Thy 1.2+ splenic lymphocytes. The level of the ACE activity was proportionate to the number of administered spleen cells. Thus, the level of ACE activity within the egg-induced granuloma is dependent upon T lymphocytes present in the spleen and granulomas of infected animals.