The humoral immune response of mice to intra-mammary immunization with ovalbumin.

Groups of lactating mice were immunized intra-mammarily on the second day of lactation with 20 micrograms, 150 micrograms or 400 micrograms of ovalbumin (OVA). This resulted in the appearance of IgG in serum, and IgA and IgG in milk. In serum, no IgA antibodies were detected 16 days after immunization in any of the groups. The serum response of IgG was variable and not related directly to the immunizing dose. Both IgA and IgG antibodies were absent in milk 5 days after immunization and IgG antibody level in milk increased significantly throughout lactation as measured 10 and 15 days after inoculation. No IgA antibodies appeared in the milk of the 20 micrograms and 150 micrograms group; however, responses appeared in milk with the highest dose (400 micrograms), but the number of responders for IgG increased in milk but not in blood. The results suggest that intra-mammary immunization can provoke a local IgA response in milk, and that serum is not a major source of IgG in that fluid. Moreover, the kinetics of the IgA and IgG responses differ.