Influence of circulating maternal antibody on the transfer of dietary antigen to neonatal mice via milk.

125I-BSA injected intravenously into lactating mice persisted in the circulation for 4 h, entered the mammary gland, and was transferred to the neonate via the milk. When injected with anti-BSA antibodies, it was rapidly cleared from the circulation. Although animals receiving anti-BSA antibodies transferred more radioactivity to the neonate via the milk, the radioactivity was not TCA-precipitable or bound to staphylococcal protein A, nor was it immunoreactive. These findings suggest that circulating maternal antibody can limit the transfer of specific protein antigen from mother to newborn.