Propionibacterium acnes (P.acnes) is isolated in high incidence from biopsied specimens obtained from patients with sarcoidosis. In some reports, P.acnes successfully produced localized granulomatous changes in experimental animals, but not systemic granulomatous changes. The present study was undertaken to analyze the formation of granulomatous lesions, especially the immunological mechanism of epithelioid granuloma formation, induced by sensitization with Corynebacterium parvum (C.parvum) and muramyl dipeptide (MDP). Intratracheal administration of MDP to guinea pigs presensitized with C.parvum produced epithelioid granulomas in the lungs and regional lymph nodes, but not in the liver and spleen. These granulomas in the lungs gradually invated regional lymph nodes and were observed a relatively long time, as the patients with sarcoidosis. An increase in lymphocytes was found in bronchoalveolar lavage fluid of sensitized animals in accordance with granuloma formation in the lungs. This result suggests that lymphocytes play a major role in producing epithelioid granulomas. Serum angiotensin converting enzyme activity was elevated in guinea pigs, in which granuloma formation was recognized. These data suggest that activation of macrophages and lymphocytes is necessary to produce epithelioid granulomas and persists for a long time in experimental animals.
experimental animal model
angiotensin converting enzyme