Serum and bile antibody responses (IgG and IgA) during subclinical Fasciola hepatica infection in sheep.

The kinetics of serum and bile immunoglobulins (IgG and IgA) directed against Fasciola hepatica in the course of subclinical infection induced experimentally was investigated in sheep. Serum activities of glutamate dehydrogenase and gamma-glutamyltransferase were used as markers of the different fluke stages during infection and associated liver damage. Specific serum and bile immunoglobulins followed a similar kinetic pattern, increasing progressively from infection throughout the prepatent period and tended to decrease when adult flukes became established in the bile duct. IgA titres were lower than those of IgG. Specific IgG and IgA bile titres reached maximum values at 14 weeks postinfection that were considerably lower than the serum titres during the whole experimental period. The major bile immunoglobulins are probably derived directly from plasma. The immunoglobulin kinetic pattern could be related to changes in serum liver enzyme activities.