A lipolytic enzyme in reactive histiocytes of guinea pigs with experimental encephalomyelitis.

A lipolytic enzyme has been demonstrated by means of a cytochemical technique and by direct chemical assay in granulomatous tissues of guinea pigs with encephalomyelitis and demyelinization resulting from the injection of an emulsion comprised of brain tissue and adjuvants, including Mycobacterium butyricum. Combined histologic and cytochemical studies showed that the lipolytic enzyme was present in the cytoplasm of a large proportion of the reactive histiocytes in the granulomatous tissue around the site of injection in the diseased animals, and that the enzyme-containing histiocytes were even more numerous in the inflamed regional lymph nodes. In control experiments, when emulsions lacking either brain tissue or M. butyricum were injected in previously normal guinea pigs, the experimental condition did not develop; under these circumstances the lipolytic enzyme was found in only a small proportion of the cells of the granulomatous tissue around the injection sites, and it was almost negligible in the regional lymph nodes of these animals. It was absent from the cells of the lymph nodes of normal animals, and from the cells of talcum and aluminum hydroxide granulomas produced experimentally in guinea pigs. The lipolytic enzyme may be a factor in the pathogenesis of the experimental encephalomyelitis and demyelinization.