Development of the capacity to produce specific antibody to an ingested food antigen in the premature infant.

Thirteen premature infants were given bovine serum albumin, a cow milk protein, by addition to their formula. Serum antibodies to BSA developed in three infants 36-38 weeks' gestation, confirming that exposure to the antigen in the gastrointestinal tract will immunize infants born after 36 or more weeks' gestation. Serum antibodies to BSA, however, were detected in only one of two infants of 35 weeks' and in none of eight infants of 30-34 weeks' gestation. The results show that the capacity to make specific antibodies to BSA develops around 35-36 weeks' gestation, despite the prior appearance of organized lymphoid tissue and independent of antigen exposure.