Secretion of IgA in the sheep following local antigenic stimulation

Abstract

The preparation is described of an antiserum specific for the locally produced immunoglobulin in whey from mammary glands of ewes infused with antigen about 1 month before lambing. In immunoelectrophoresis, the antiserum failed to react or reacted weakly with serum and with colostral whey from non-infused glands of primiparous ewes but reacted strongly with a protein of β-electrophoretic mobility in the colostrum and milk from infused glands. The majority of the antibody in whey from antigen-infused glands was eluted from DEAE Sephadex by buffer of relatively high ionic strength in association with the antigenically stimulated protein. Antibody activity in these fractions was heat stable. The antigenically stimulated protein was shown to be a carbohydrate-rich immunoglobulin distinct from IgG₁, IgG₂ and IgM. It is concluded that it is analogous to IgA of other species.

Comparison of the antigens in serum and whey reactive with the specific antiserum gave no evidence for the existence of an additional antigenic component associated with the IgA in whey. IgA was readily detected in whey from non-infused glands of older multiparous ewes, in the contents of the small intestine but not in concentrated mixed saliva. It is suggested that antigenic stimulation of mammary glands and probably some other mucous surfaces of ewes awakens an almost dormant local system of antibody production analogous to the IgA system in other species.