Experimental hypersensitivity pneumonitis in the mouse: histologic and immunologic features and their modulation with cyclosporin A.

A murine model of hypersensitivity pneumonitis (HP) was established with transnasally administered Thermoactinomyces vulgaris (Tv) bacilli. Bronchoalveolar lavage (BAL) of experimental animals revealed marked increase in the total cell, lymphocyte, and macrophage numbers; the findings were similar to those in human HP. The BAL lymphocytes were mostly Thy 1.2 positive. Lyt-1 positive cells predominated Lyt-2 positive cells. Anti-Tv IgG antibodies and delayed-type hypersensitivity footpad reactions against Tv were detected in animals with HP. Cyclosporin A (CyA), a potent immunosuppressive drug, had marked effects on the development of HP in this model. When CyA was administered throughout the course of Tv inoculations, the granulomatous pneumonitis was markedly suppressed, and an increase in BAL lymphocytes, Thy 1.2 positive cells, was suppressed. When CyA was administered only during the first half period of the Tv treatment, suppression of the disease was minimal; when CyA was administered in the latter half, both the HP lesions and the increase in BAL cell lymphocyte numbers were significantly suppressed. These results indicate that a series of transnasal administration of Tv in mice may provide a good model for human HP.