Fasciola hepatica: influence of thymus function on the liver pathology in mice.

Liver pathology during experimental Fasciola hepatica infection was compared in thymus-deficient (nu/nu) mice and in thymus-bearing (+/+) mice, (back ground strain to nu/nu mice) and thymus-reconstituted nu/nu mice. Thymus deficiency resulted in unrestricted liver damage during the migration of the parasite in the liver. In nu/nu mice the migratory tracks were infiltrated by very few eosinophils and mononuclear cells, haemorrhages and liver cell necroses were extensive. Portal area reaction and bile duct hyperplasia were depressed. Regeneration of liver tissue, parenchymal and periportal fibrosis and plasma cell proliferation were reduced. The possible causal mechanisms involved in fluke induced liver pathology are discussed. It is suggested that a thymus-dependent cellular reaction modulates the tissue damage produced by F. hepatica.