HISTOPATHOLOGY OF PARACOCCIDIOIDOMYCOTIC INFECTION IN ATHYMIC AND EUTHYMIC MICE - A SEQUENTIAL STUDY

We report the comparative and sequential histologic analysis of lesion s developed by Paracoccidioides brasiliensis-infected athymic and euth ymic BALB/c mice, using conventional and specific stain to characteriz e the morphology of fungi and inflammatory cells as well as the extrac ellular matrix patterns. In both groups, neutrophils and macrophages w ere the predominant cells; macrophage transition to giant and epitheli oid cells was observed. Degenerated fungi and fungal dust were associa ted with local neutrophil infiltration and the presence of pseudoxanto matous macrophages. Paracoccidioides brasiliensis are always found wit hin an extracellular matrix microenvironment. The main differences bet ween lesions developed by nu/+ and nude (nu/nu) mice resided in the mo re pronounced encapsulating tendency in the former ones. In both group s of animals, lesions in several organs were associated with extensive hemopoiesis. At the first week of infection, there was evidence of fu ngal destruction and control of its proliferation in both mouse groups . At the fourth and seventh weeks, nu/+ mice maintained the control of the infection, as shown by the scarce numbers of budding yeast cells, while experimental nu/nu mice showed a tumorlike progression of the d isease with a striking increase in fungal load in many organs (e.g., o mental and mesenteric milky spots, lymph nodes, spleen), some of which present their structure replaced by granulomatous lesions.