Immunological Tolerance to Pig-serum Partially Inhibits the Formation of Septal Fibrosis of the Liver in Capillaria hepatica- infected Rats

Systhematized septal fibrosis of the liver can be induced in rats either by repeated intraperitoneal injections of pig-serum or by Capillaria hepatica infection. The relationship between these two etiological factors, as far as hepatic fibrosis is concerned, is not known, and present investigation attempts to investigate it. C. hepatica-induced septal fibrosis of the liver was considerably inhibited in rats previously rendered tolerant to pig-serum. Pig-serum-tolerant rats developed antibodies against pig-serum when infected with C. hepatica, but this did not happen when the infection occurred in normal rats. On the other hand, anti-C. hepatica antibodies failed to recognize any epitope in pig-serum, by Western blot. However, no evidence of an immunological cross reactivity was found, at least at the humoral level. Alternatively, cell-mediated mechanisms may be involved, and further investiga-tions are warranted. Key words: pig-serum model- Capillaria hepatica- hepatic septal fibrosis Rats infected with the helminth Capillaria hepatica invariably develop a peculiar type of hepatic fibrosis, 30-40 days after inoculation. By the time the worms are usu-ally dying and disintegrating, and while the focal necro-inflammatory lesions around them are exhibiting evidences of resorption, septal fibrosis starts throughout the liver (Ferreira & Andrade 1993). Morphologically, it has close similarity to the fibrosis experimentally induced in rats by repeatedly intraperitoneal injections of pig-serum or by its albumin fraction (Paronetto & Popper 1966, Ballardini et al. 1985, Andrade 1991, Bhunchet et al. 1996). In both cases the histological picture is dominated by fine and long fibrous septa, that crisscross the hepatic parenchyma, forming a mosaic pattern, sometimes reminiscent of the pig liver, that progressively may evolve toward a final morphological picture of cirrhosis (Paronetto & Poppe