CALOMYS CALLOSUS - AN ALTERNATIVE MODEL TO STUDY FIBROSIS IN SCHISTOSOMIASIS-MANSONI - THE PATHOLOGY OF THE ACUTE-PHASE

Twenty Calomys callosus, Rengger 1830 (Rodentia - Cricetidae) were stu died in the early stage of the acute schistosomal mansoni infection (4 2nd day). The same number of Swiss Webster mice were used as a compara tive standard. Liver and intestinal sections, fixed in formalin-Millio ning and embedded in paraffin, were stained with hematoxilin and eosin , PAS-Alcian Blue, pH=1, 0 and 2, 5, Lennert's Giemsa, Picrosirius plu s polarization microscopy, Periodic acid methanamine silver Gomori's s ilver reticulin and resorcin-fuchsin. Immunohistological study (indire ct immunofluorescence and peroxidase labeled extravidin-biotin methods ) was done with antibodies specific to pro-collagen III, fibronectin, elastin, condroitin-sulfate, tenascin, alpha smooth muscle actin, vime ntin and desmin. The hepatic granulomas were small, reaching only 27% of the volume of the hepatic Swiss Webster granuloma. They were compos ed mainly by large immature macrophages, often filled by schistosomal pigment, characterizing an exsudative-macrophage granuloma type. The g ranulomas were situated in the parenchyma and in the portal space. The y were often intravascular; poor of extracellular matrix components, e xcept fibronectin and presented, sometimes alpha smooth muscle actin a nd vimentin positive cells. The C. callosus intestinal granulomas were similar to Swiss Webster showing predominance of macrophages. Therefo re, the C. callosus acquire very well the Schistosoma mansoni infectio n, without developing strong hepatic acute granulomatous reaction, sug gesting lack of histopathological signs of hypersensitivity.