Cytokines produced by suscesptible and resistant mice in the course of Paracoccidioides brasiliensis infection

Paracoccidioidomycosis (PCM) is the most prevalent deep mycosis in Latin America and presents a wide spectrum of clinical manifestations. We established a genetically controlled murine model of PCM, where A/Sn mice develop an infection which mimics the benign disease (immune responses which favor cellular immunity) and B10.A animals present the progressive disseminated form of PCM (preferential activation of B cells and impairment of cellular immune responses). To understand the immunoregulatory phenomena associated with resistance and susceptibility in experimental PCM, A/Sn and B10.A mice were studied regarding antigen-elicited secretion of monokines (TNF-alpha and TGF-beta) and type-1 (IL-2 and IFN-gamma) and type-2 (IL-4,5,10) cytokines. Total lymph node cells from resistant mice infected ip with P. brasiliensis produced early and sustained levels of IFN-gamma and IL-2; type-2 cytokines (IL-4 and IL-05) started to appear 8 weeks after infection. In contrast, susceptible mice produced low levels of IFN-gamma concomitant with significant levels of IL-5 and IL-10 early in the infection. In the chronic phase of the disease, susceptible animals presented a transitory secretion of IL-2, and IL-4. In the pulmonary infection IL-4, IL-5 and IL-10 were preferentially detected in the lung cells washings of susceptible animals. After in vitro challenge with fungal antigens, normal peritoneal macrophages from B10.A mice secreted high levels of TGF-beta and low levels of TNF-alpha. In contrast, macrophages from A/Sn animals released high levels of TNF-alpha associated with a small production of TGF-beta. The in vivo depletion of IFN-gamma not only abrogated the resistance of A/Sn mice but also diminished the relative resistance of B10.B animals. The in vivo depletion of IL-4 did not alter the disease outcome, whereas administration of rIL-12 significantly enhanced resistance in susceptible animals. Taken together, these results suggest that an early secretion of high levels of TNF-alpha and IFN-gamma followed by a sustained secretion of IL-2 and IFN-gamma plays a dominant role in the resistance mechanisms to P. brasiliensis infection. In contrast, an early and ephemeral secretion of low levels of TNF-alpha and IFN-gamma associated with production of IL-5 IL-10 and TGF-beta characterizes the progressive disease of susceptible animals.

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