Lack of IgA antibody response in secretions of rat dams during long-term ovalbumin feeding. Induction of systemic tolerance in pups but not in adult rats.

Antigen uptake, serum and secretory immune response was studied in rat dams fed pellets substituted with ovalbumin during three consecutive pregnancies and lactation periods. The concentration of ovalbumin was somewhat higher in milk than in serum, and both serum and milk concentrations showed a parallel decrease with feeding time. IgA antibodies did not develop in the milk during the 7-month feeding period and no antibody response could be detected in saliva or bile. By the time of the first lactation about half of the dams had developed low titres of IgG antibodies in serum and milk and the number of IgG responders, as well as the mean antibody titre, increased with each lactation. Also when injected directly into the Peyer's patches ovalbumin induced solely IgG antibodies in the milk, while immunization with ferritin in addition resulted in both IgA and IgM antibodies in the milk against ferritin. The presence or absence of immunological tolerance to ovalbumin was examined in three groups of rats: (1) dams which had been fed ovalbumin-substituted pellets for one pregnancy and the first 14 days of the lactation period, i.e. for approximately 5 weeks altogether; (2) pups that were born by and kept together with these mothers, and (3) pups that were born by and kept together with mothers that were fed ovalbumin-substituted pellets during the pregnancy and until weaning at day 21 (altogether for 6 weeks). The rat dams in group 1 were not tolerant to a subcutaneous injection of ovalbumin 4 weeks after the termination of feeding with ovalbumin-substituted food.(ABSTRACT TRUNCATED AT 250 WORDS)