Decreased response of human milk leukocytes to chemoattractant peptides

To test the hypothesis that neutrophils and macrophages in human milk may not defend by classical inflammatory mechanisms, experiments were conducted to ascertain whether adherence, orientation, and directed motility of these leukocytes would be enhanced by exposure to chemoattractant peptides including N-formyl-L-methionyl-L-phenylalanine and N-formyl-L-methionyl-L-leucyl-L-phenylalanine and C5a generated from zymosan activated human serum. Adherence and spatial orientation were tested on coverglasses and in Zigmond chambers, and chemotaxis was examined by Boyden chambers and a subagarose technique. Whereas, the adherence, orientation, and directed movement of adult peripheral blood neutrophils and monocytes were significantly enhanced by those chemotactic agents, human milk leukocytes failed to respond. The failure of the response of human milk leukocytes was not due to alterations in maternal peripheral blood leukocytes but appeared to be due partially to inhibitors in human milk. The experiments suggest that human milk leukocytes may be modified in the mammary gland to protect by noninflammatory mechanisms.