Experimental Hypersensitivity Pneumonitis in Mice Induced by Trichosporon cutaneum: Histologic and Immunologic Features and Effect of in Vivo Depletion of T Cell Subsets

An animal model of hypersensitivity pneumonitis (HP) was developed in C57Black/6J mice by repeated intratracheal inoculations with particulate Trichosporon cutaneum, a causative agent of Japanese summer-type HP. We observed severe alveolitis and bronchiolitis with infiltration of lymphocytes, macrophages, and neutrophils in the lung lesions. Granuloma formation was occasionally seen. Bronchoalveolar lavage (BAL) of the experimental animals showed an increase in the number of lymphocytes, macrophages, neutrophils, and in the total cell yield. Phenotypic analysis of the BAL lymphocytes by flow cytometry revealed that 43.1 ± 3.1% of lymphocytes were Thy1.2+ (CD3+) cells and that the L3T4 + (CD4+) cells (36.3 ± 3.5%) predominated over the Lyt2+ (CD8+) cells (18.5 ± 1.2%). As for the humoral immune response, the specific IgA antibody activities in the BAL fluids well reflected the specific pulmonary inflammatory responses. Studies of lymphocyte depletion were performed by in vivo administration of anti-CD4 and...