Experimental paracoccidioidomycosis in high and low antibody responder mice of Selection IV-A

High (H) and low (L) responder mice were selected for their ability to prod uce antibodies against sheep and human erythrocytes (Selection IV-A). In th is selection, the difference in antibody responsiveness between H and L lin es (HIV-A and LIV-A mice, respectively) was shown to depend mainly on macro phage function. The more rapid catabolism of antigens by macrophages in L m ice has been suggested as the main cause of the low antibody production. Du e to this high macrophage activity, L animals have been described as more r esistant than H animals to intracellular pathogens. These animals were util ized as an experimental model of paracoccidioidomycosis. HIV-A and LIV-A mi ce were infected with Paracoccidioides brasiliensis by the intravenous rout e. As expected, H mice were more susceptible to P. brasiliensis with a shor ter survival time and higher levels of specific antibodies when compared to L mice. Contrasting with the survival time, the lungs, spleen and liver fr om H mice showed typical nodular granulomas containing epithelioid and gian t cells and few fungi. On the other hand, in LN-A mice, the lesions of thes e organs were characterized by looser granulomas with irregular borders and the presence of a large number of fungi, However, the adrenal gland showed different lesion patterns. In H mice these lesions were extensive and char acterized by loose granulomas with numerous fungi, while in LIV-A mice the lesions were small and limited to the cortex. Moreover the HIV-A mice prese nted higher levels of serum corticosterone when compared to LIV-A ones. The higher susceptibility of H mice could be attributed to the extensive lesio ns of the adrenal glands. These results suggest the use of the H line from the IV-A Selection as an experimental model for further studies of adrenal involvement in paracoccidioidomycosis.