Experimental pulmonary candidiasis in modified rabbits. II. Immunohistochemical evidence of participation of immune complexes in the formation of fungal lesions in C. albicans-sensitized hosts.

Pulmonary lesions induced by an intratracheal inoculation of Candida albicans into rabbits in untreated control, bovine serum albumin (BSA)-sensitized and C. albicans-sensitized groups were examined immunohistochemically to clarify the localization of IgG, IgM and C3. In the control group no inflammatory cells were immunoreactive for IgG and only a few macrophages for IgM and C3, whereas in the BSA- and C. albicans-sensitized groups there were a small number of IgG-positive polymorphonuclear leukocytes and IgM- and C3-positive macrophages in the lesions, the latter group being more prominent. Furthermore, epithelioid granulomatous lesions at the late stage in the C. albicans-sensitized animals showed scattered epithelioid cells containing IgG as well as abundant IgG- and IgM-positive plasma cells. These immunohistochemical results were considered to support the estimation that immune complexes contributed to the modification of fungal lesions in the C. albicans-sensitized hosts, although non-immunological defense mechanisms seemed to be more important in the elimination of the fungus.