Immunologic benefits and hazards of milk in maternal-perinatal relationship.

Aside from nutritional significance, milk affords infant mammals immunologic benefits. However, it is not without immunologically based hazards. These stem from its antigenicity and the fact that in certain species that receive their maternal immunologic endowment postpartum, hemolytic disease of the newborn may be mediated by colostral antibodies. Awareness that viable leukocytes are ingredients of colostrum and milk has stimulated interest in the significance of these cells. Skin grafting tests on foster-nursed rats and mice have given circumstantial evidence that, in these species, leukocytes may be transmitted naturally from the mother's blood stream to the suckling's blood stream through the milk, and that these cells may be beneficial (adoptive immunization) or, in some genetic contexts, harmful (initiating graft-versus-host disease). In man, too, studies on necrotizing enteritis and other disease provide increasing support for the thesis that leukocytes in milk fulfill a protective function, possibly as a consequence of their "natural" transplantation.