Neutrophil Leukocyte as a Source of Lactoferrin in Bovine Milk

Abstract

SUMMARY The lactoferrin ( lf ) concentration of bovine blood and milk neutrophilic polymorphonuclear leukocytes ( pmn ) was determined and an estimate made of the pmn contribution to the elevated lf concentrations in milk during inflammation of the mammary gland. The mean blood and milk pmn concentrations of lf were 8.63 and 2.98 μg/10 6 pmn , respectively. It was suggested that this difference may be due to the phagocytosis of fat and degranulation by milk pmn , causing lf release. The results of immunoperoxidase staining of blood leukocytes indicated that lf was found only in pmn as no lf was detectable in bovine eosinophils, lymphocytes, or monocytes. Staining for lf appeared to be limited to the cytoplasm. Increases in lf values in milk during endotoxin-induced mammary gland inflammation were preceded by increased somatic cell counts (94% pmn ). It was estimated that an average of 4.9% of the peak lf levels in whey could have come from the pmn , suggesting this cell is not the major source of lf in milk during mastitis.