ABSTRACT
The first century of study of the endemic mycotic diseases is coming to a close. While nomenclature of the organisms varied during Vie early years, the systemic infections that we now know are caused by the four primary endemic fungi; Coccidioides immitis, Blastomyces dermatitidis, Histoplasma capsulatum, and Paracoccidioides brasiliensis, which were first reported in 1891, 1894, 1901, and 1908, respectively [1-4]. The diseases caused by these pathogenic fungi are primarily acquired by inhalation of the infectious particle from the mycelial phase of the organisms growing in the soil of indigenous areas. Once inhaled, these organisms undergo a morphological conversion into the parasitic phase, which, for B. dermatitidis, H. capsulatum, and P. brasiliensis, is typically budding yeast. The C. immitis parasitic cycle is more complex and has multiple forms ranging from the 3-to 5-,...m endospore to the 60-to 80-,...m spherule [5]. This dimorphic life cycle is interwoven in that, the parasitic phase cells can convert back into the mycelial form when culture conditions are changed or the organism is seeded to the soil. Increased temperature and/or CO2 concentration appear to be the primary factors in the saprobic to parasitic phase conversion [6,7]. During this primary conversion, the host is exposed to antigens from both saprobic and parasitic phase cells. Thereafter, with rare exception, the host is primarily responding to the parasitic phase cells and derived antigens. This review will attempt to coalesce current observations on induction of protective cell-mediated immunity against the endemic fungi, with special emphasis on C. immitis and H. capsulatum, and with contributions from other fungal model systems, notably Cryptococcus neoformans and Candida albicans.
