The leukocyte as a defense mechanism
Paape, M.J.; Wergin, W.P.
Journal of the American Veterinary Medical Association 170(10 Pt 2): 1214-1223
1977
ISSN/ISBN: 0003-1488 PMID: 873837 Document Number: 112610
Within the udder, neutrophil polymorphonuclear (PMN) leucocytes are capable of phagocytosing a wide variety of particles (microorganisms, milk fat globules, casein). Studies of PMN leucocyte function indicate that milk fat globules and casein are perhaps significant deterrents to phagocytosis and destruction of Staphylococcus aureus by PMN leucocytes in milk. These deterrents could be a major factor in establishment of intramammary infections by invading mastitis pathogens. Elimination of fat and casein from milk during clinical or subclinical mastitis may free PMN leucocytes to function properly and may remove infection from the mammary gland. Further observations on PMN leucocyte function indicate that considerable variation exists among cows in the ability of whole milk and skim milk to support phagocytosis and in the ability of PMN leucocytes to phagocytose. Variation in this basic defense mechanism could account for the differences that exist in susceptibility to infection by mastitis pathogens.