The interaction in vitro between bovine immunoglobulin and juvenile Fasciola hepatica

Freshly excysted Fasciola hepatica possess an outer glycocalyx which stimulates an antibody response in cattle infected with F. hepatica metacercariae. Sera from animals receiving either a single or a double infection were examined for levels of IgM, IgG1 and IgG2 specific for the outer glycocalyx of intact live juvenile F. hepatica. High levels of specific IgG1 were found to predominate. Using positive sera in an indirect fluorescent antibody assay, the bovine immunoglobulins labelled the outer glycocalyx in a characteristic reticulated pattern. On incubation at 37 degrees C this pattern rapidly broke up into discrete clumps and progressed until the entire antibody-outer glycocalyx complex was shed. The shedding phenomenon was shown to be continuous and, by using preparations of Fab fragments, was not due to the bivalent binding of the sensitizing antibody.