Colostral leukocytes

Leukocytes of human colostrum were studied for their phagocytic activity and ability to migrate in vitro. Samples were collected from healthy females in the first 2 weeks after delivery. Leukocytes were found with great regularity in concentrations of 2200–4100/mm3. These colostral leukocytes displayed glass adhesiveness, amoeboid movement, and the ability to migrate in capillary tubes. The phagocytic activity of colostral leukocytes against nonencapsulated Cryptococcus neoformans approached the normal values of peripheral blood leukocytes. The colostral leukocytes reacted to specific antigen similar to the donors' peripheral blood leukocytes and correlated with the dermal reactivity of the donor. The finding that these leukocytes are in relatively large numbers and possess phagocytic activity supports the concept that this is a naturally occurring in vivo phenomenon and that these cells may protect the breast against invading microorganisms; also, since these cells demonstrate the presence of cell‐mediated hypersensitivity and are normally ingested by the neonate, they may play a role in the development and/or induction of cellular immunity in the neonate.