Oral immunization to milk protein in human infants in the presence of passive antibody.

The possible influence of maternal antibody on the immune response to bovine serum albumin (BSA), a normal cow's milk protein, was investigated in fullterm human neonates. Antibody production to BSA of 12 infants with passively acquired anti-BSA (Group I) was compared to the immune response of nine infants without passive anti-BSA at birth (Group II) during the first 6 months of life. All infants were raised on commercial cow's milk formulas containing BSA in concentrations from 0.4-4.0 mg/dl. From 4 wk of age concentrations of circulating anti-BSA as measured by radioimmunoassay and enzyme-linked-immunosorbent-assay (ELISA) were higher in Group II, but differences were not statistically significant. There was no differences in the immune response between infants ingesting formulas with high BSA content compared to infants ingesting low concentrations of antigenic BSA. The main isotype associated with anti-BSA formation was IgG. IgA in measurable amounts appeared later and accounted for approximately 10% of circulating antibody in both groups at 6 months of age. Ony small amounts of IgM- and IgE-anti-BSA were detected.