Evidence for transmission of lymphocyte responses to tuberculin by breast-feeding.

The possibility that cell-mediated immunity could be acquired by breast-feeding was evaluated in a prospective study of 26 tuberculin positive and 9 negative puerperal mothers and their infants. 13 infants of the positive and all the infants of negative mothers were breast-fed. Tuberculin-reactive T cells were found in colostrum and early milk of most positive but in none of the negative nursing mothers. A significant number (8/13) of infants born to positive mothers had tuberculin-reactive peripheral blood T cells after 4 weeks of breast-feeding compared with bottle-fed infants (1/13) of positive mothers or breast-fed infants (0/9) of negative mothers. Examination of cord blood for tuberculin-reactive T cells provided no significant evidence of transplacental transmission of responsiveness to tuberculin. The results suggest that breast-fed infants may passively acquire T cell responsiveness to a specific antigen by ingestion of breast milk.