Paracoccidioidomycosis in silica-treated rats

An attempt is made to evaluate the importance of macrophages in the early local reaction to infection caused by the fungus Paracoccidioides brasiliensis. With this purpose, an attempt was made to impair macrophagic activity in the site of the fungal inoculum, by means of previous injections of silica. Twenty male rats were intraperitoneally infected with yeast cells of the fungus. Ten of the rats were injected intraperitoneally with silica particles twice, namely 24 and 4 h before the infection. All the animals were killed 4 wk after fungal inoculum. The results showed that the disease was aggravated in rats pre-treated with silica, clearly demonstrated by the 100% metastatic pulmonary involvement, in contrast with only 40% observed in the non-treated controls.