Kinetic responses of parasite-specific antibody isotypes, blood leucocyte pattern and lymphocyte subsets in rats during primary infestation with Fasciola hepatica.

Antibody responses, blood leucocyte and splenic lymphocyte subset patterns were studied during a primary infection with Fasciola hepatica in the rat. The infection induced parasite-specific IgM by 2 weeks after infection. High levels of IgM antibodies were maintained for many weeks. The IgE response was biphasic with peaks at 5 and 9 weeks after infection which were correlated with different phases in the development of F. hepatica in the rat. Both IgG2a and IgG1 antibodies were detected but the titre of IgG2a augmented slightly and rose more slowly than did that of IgG1. There was a rise in neutrophil and eosinophil numbers. Neutrophils did not increase before the fourth week but eosinophil numbers were raised by the second week after infection and remained high during the whole migratory phase of the parasite. In the spleen, the percentage of B lymphocytes increased and there was a decrease in the percentages of CD4+ and CD(8+)-like T lymphocytes. These results suggested that, in the rat infested with F. hepatica, TH2-like lymphocytes could be preferentially stimulated, as has been reported in murine schistosomiasis.