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Polymorphonuclear leukocytes (PMN) from human colostrum were compared with blood and oral exudate PMN from the same donors for their locomotive, respiratory burst, phagocytic, and shape change (polarization) capabilities. Blood PMN were functionally superior to PMN from other sites. Colostrum PMN were similar to oral exudate PMN in all areas except locomotive responses. Exposure of blood PMN to aqueous human colostrum resulted in decreased stimulated adherence to plastic, decreased bactericidal activity against Staphylococcus aureus, reversible induction of cellular shape change, and reversible decreases in cellular deformability. The colostrum effects on PMN shape change and deformability were accompanied by significant increases in cytoskeleton-associated actin. PMN isolated from colostrum have suppressed functions, consistent with their being exudate cells. In addition, the colostrum environment effectively suppresses multiple functions in PMN from blood, these effects being mediated in part by rapid cytoskeletal assembly. PMN in colostrum do not appear to be beneficial to the breast-fed infant due to deficiencies in function.

Summary Human colostrum contains several antioxidants which prevent the detection of human polymorpho-nuclear leukocyte (PMN) respiratory burst products. Using column chromatography to fractionate colostrum, two peaks of antioxidant activity were resolved away from colostral proteins and further characterized. One peak contained both cytochrome c-reducing activity and H2O2-depleting activity. This peak had the chromatographic, spectral, and antioxidant characteristics of ascorbate, and by high performance liquid chromatography (HPLC) methods, was shown to contain ascorbate as well as at least four other materials. The antioxidant activity in this peak was totally ascorbate oxidase sensitive and partially uricase sensitive. The other peak contained only H2O2-depleting activity and had the chromatographic, spectral, and antioxidant characteristics of uric acid. By HPLC, uric acid was the only component in this peak and its antioxidant activity was completely uricase sensitive and ascorbate oxidase resistant. Colostral uric acid levels were measured in eight postpartum women and found to be approximately one-third of simultaneously determined serum uric acid levels. Colostrum contains at least two separate antioxidants, one of which is ascorbate-like and the other is uric acid. We speculate that these antioxidants may function in human colostrum as traps for neutrophil-generated reactive oxygen metabolites.