The interactionin vitrobetween bovine immunoglobulin and juvenileFasciola hepatica

Abstract

SUMMARY: Freshly excystedFasciola hepaticapossess an outer glycocalyx which stimulates an antibody response in cattle infected withF. hepaticametacercariae. Sera from animals receiving either a single or a double infection were examined for levels of IgM, IgG₁and IgG₂specific for the outer glycocalyx of intact live juvenileF. hepatica. High levels of specific IgG₁were 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 °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.