Experimental paracoccidioidomycosis in high and low antibody-producer mice. I.--Evolution of the disease, its correlation with the humoral immune response and the patterns of tissue lesions.

High (H) and low (L) responder mice selected for their capacity to produce antibody against flagellar antigens of Salmonellae sp. were infected i.p. with 10(6) L forms of Paracoccidioides brasiliensis, strain 18. In H mice, the mortality ratio was 50%; the splenic index was high at the onset of infection (1.0), decreasing to normal levels after 30 days (0.45), with antibody titres such as 4-5 log2. In L mice, the mortality was 87.5%, the splenic index was above 0.6 and the antibody titres after 30 days were below 2 log2. In L mice, granulomas containing a high number of fungi, epithelioid cells, macrophages and a few polymorphonuclear cells were found. In H mice, focal or diffuse infiltrate of mononuclear cells with few or even the absence of fungi was seen. The passive transfer of immune ascitic fluid to L mice induced a reduction in the number of granulomas and fungi in the lesions.