Immunohistochemical demonstration of TGF-ß and decorin in paracoccidioidal granulomas

Different patterns of granulomas have been observed in 6- to 8-week-old mice after ip inoculation with 5 x 10(6) yeast cells of Paracoccidioides brasiliensis. Transforming growth factor-ß (TGF-ß) is a cytokine that has been shown to participate in fibrosis and granuloma formation; its activities seem to be modulated by the small proteoglycan decorin. In the present study, TGF-ß and decorin expression in epiploon granulomas was assessed by immunohistochemistry in susceptible (B10.A) and resistant (A/J) mice after 15, 30, 120 and 150 days of P. brasiliensis ip infection. The epiploon was collected, fixed in Methacarn solution and embedded in paraffin, and 5-æm thick sections were used for immunohistochemical analysis employing the streptavidin-biotin-peroxidase technique. The former mouse strain developed fatal disease with many disseminated lesions increasing in size and number during the infection and the latter developed mild disease with the presence of encapsulated granulomas. In the epiploon, TGF-ß was present on macrophages, giant cells, lymphocytes and fibroblasts, and absent on neutrophils. It was also detected in areas of fibrosis and necrosis, as well as disperse in amorphous extracellular matrix, mostly in resistant mice. Decorin was present circumscribing macrophages and giant cells containing fungi, but absent on these cells. In both mouse strains, decorin was found at the periphery of the lesions, and markedly in milky spot granulomas. In resistant mice, positivity was found around fibrotic and necrotic areas of encapsulated and residual lesions containing lysed fungi. Decorin was found associated with thick fibers around encapsulated lesions. In susceptible mice, the size and number of lesions increased with the progression of the disease and were correlated with the weaker expression of decorin. We suggest an association of decorin with the fibrogenic process observed in paracoccidioidal granulomas

Fibrosis patterns of lesions developed by athymic and euthymic mice infected with Paracoccidioides brasiliensis

Athymic and euthymic mice with BALB/c background were used to study the patterns of fibrosis during ip infection with a virulent isolate of Paracoccidioides brasiliensis. Specimens from various organs were collected from the animals at 1,4 and 7 weeks after infection and observed under light microscopy using various histologic staining methods. Lesions from the first week of infection, in both animal groups, presented a predominance of collagen III over I, carboxylated proteoglycans, and a tendency to encapsulation. From 4 weeks onward, the lesions of nu/+mice tended to involute to macrophage-pseudoxanthomatous aggregates or to encapsulation with an increase of collagen I and sulfated proteoglycans. On the contrary, with the evolution of the infection, the nu/nu mice displayed permanently active lesions, rich in reticular fibers and carboxylated proteoglycans, with varied amounts of collagens III and I, without or with minimal encapsulation. However, independent of the type of mice, or of the type of lesions, the minimal P. brasiliensis-ECM unit was formed by a fibrillar cocoon of reticular fibers that encloses an individual yeast or a "family" composed of a mother cell plus one or various peripheral daughter cells, alone or engulfed by macrophages or giant cells. The overal difference of the lesions of nude and normal mice was not in isolated aspects of their components, but in the general architecture of the lesions. Those of nu/+mice were either of involutive or of encapsulated type (slightly active), and those of nu/nu mice were of the sustained-expansive type (very active), without or with minimal encapsulation