Maternal-neonatal interactions and human breast milk.

The mammary glands are a uniquely designed extension of the mucosal immune systems of the gut and bronchus. The soluble and cellular products of lactation, in which immunologic selectivity and specificity exist, link the suckling neonate irrevocably to the immunologic and infectious experience of its mother. The immune competence of the breast and products of lactation are actively and constantly in flux, dependent on the mother's hormonal, environmental, and immunologic milieu. Most of the recent human investigation has focused primarily on milk immunoglobulin specificity. More work needs to be done on the role of passively transferred cellular products, the antiviral, antiprotozoan, and antitumor capabilities of milk, and on the mechanisms by which maternal immunizations or infections may influence the outcome of host-pathogen interactions in the suckling neonate.