Detection of alpha 2-macroglobulin, alpha 1-protease inhibitor, and neutral protease-antiprotease complexes within liver granulomas of Schistosoma mansoni-infected mice.

In schistosomiasis mansoni the parasite egg-induced granulomatous tissue inflammations resolve by fibrosis. Intralesional collagen synthesis and deposition are influenced by collagenase, elastase activity that is diminished at the chronic stage of the disease. To determine the cause of diminished neutral protease activity, the authors determined levels of the antiprotease/alpha 2-macroglobulin (alpha 2M) and alpha 1-protease inhibitor (alpha 1Pi) in extracts or secretions of liver granulomas of infected mice. By ELISA, both antiproteases were detected in granuloma-derived substances, as well as supernatants of cultured, adherent granuloma macrophages. In all samples, alpha 2M was the predominant inhibitor. Antiprotease levels were similar in granuloma-derived samples obtained from acutely and chronically infected mice. However, supernatants of cultured adherent macrophages isolated from granulomas of mice with acute infection contained levels of protease inhibitors several times higher than those of similar preparations obtained from chronically infected animals. Gel filtration of samples on Sephacryl S-200 columns did not separate collagenase and elastase from protease inhibitors. By chromatofocusing, a few inhibitor-free collagenase as well as enzyme-free alpha 2M and alpha 1Pi-active peaks were eluted. The bulk of the material that eluted at the acidic region contained protease-antiprotease activity indicating the presence of enzyme-inhibitor complexes. The intragranulomatous presence of antiproteases complexed with protease enzymes emphasizes their importance in the possible enhancement of fibrosis.