Early induction of secretory immunity in infancy: specific antibody in neonatal breast milk.

Neonatal breast milk from 50 babies aged between 2 and 39 days was studied for the presence of antibody to the cows' milk protein beta lactoglobulin. Specific IgA antibody and specific secretory antibody to beta lactoglobulin were detectable towards the end of the second week of life in milk secreted by neonates fed cows' milk formula. Specific antibody concentrations were independent of total IgA concentrations. Babies receiving little or no cows' milk protein did not produce antibody in neonatal breast milk. Antigen specific mucosal immune responses develop in tissues distant from the site of primary mucosal exposure by the end of the second week of life in term human neonates, suggesting that prophylactic immunisation against enteric or other mucosal pathogens within a few days of birth may provide antibody responses in secretions, which may protect against mucosal infection.