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.
PIP: Although milk provides infant mammals nutritional and immunologic benefits, it is not without immunologically-based hazards. The hazards are based on the antigenic status of milk and the fact that in certain animals that receive their maternal immunologic endowment postpartum, hemolytic disease of the newborn may be mediated by colostral antibodies. Laboratory experiments in rats suggest the possibility that birth does not necessarily preclude further transmission of viable leukocytes from maternal to infant tissues and that this may bring about certain immunologic hazard in certain genetic contexts (initiating graft vs. host disease). Studies in human infants strongly suggest however that milk is a better diet for the newborn than the manufacturer's artificial milk formula. There is a need to reevaluate the biological significance of the female breast and deemphasize its status as a symbol of femininity.