[Review article: colostral leukocytes and their significance for the immune system of newborns].

The colostrum contains a comparably high concentration of leukocytes as the peripheral blood. The majority of them are vital leukocytes, namely neutrophils, macrophages and lymphocytes. There is some evidence in mouse and man that lymphocytes from the gut-associated lymphoid tissue home selectively to the peripartal mammary gland. The phagocytic cells may be involved in the transportation of certain immunoglobulins into the neonate. In vitro colostral leukocytes exhibit a variety of immunological activities such as blastogenesis after mitogenic and antigenic stimulation, cytotoxicity and phagocytosis, but the medium milk confines these activities in comparison with those of blood leukocytes. Intact colostral leukocytes reach the gut of the gut of the newborn and may even cross the intestinal wall, gaining access to the neonates system and influencing its immunologic reactions, e.g. hypersensitivity and antibody-formation. The knowledge on the significance of colostral leukocytes for the protection against infection of the neonate is still limited.