NEUTROPHIL FUNCTION IN-VITRO - DIAPEDESIS AND PHAGOCYTOSIS

The function of neutrophils within the mammary gland was modeled in vi tro to include diapedesis and phagocytosis. The bovine mammary cell li ne, MAC-T3, provided a mammary epithelial monolayer for use as a biolo gically meaningful barrier to neutrophil diapedesis. Features . includ ed characteristic transepithelial resistance, tight junctional complex es, and polarity. Continuous readings of transepithelial resistance in dicated a stable resistance over several hours. Staphylococcus aureus, at concentrations of 1 x 10(7) and 2 x 10(9) cfu/ml, did not appear t o have any deleterious effects on monolayer integrity over short-term (I to 2 h) exposure. Neither resting nor challenged neutrophils caused short-term damage to the monolayer. Transepithelial resistance of the monolayers remained unchanged even as neutrophils were actively migra ting through the monolayer. Further work using the MAC-T3 cell line an d electrical resistance to assess cell monolayer integrity could provi de much insight into the mechanisms underlying degeneration of mammary epithelial cells. The ability of neutrophils to phagocytose foreign p articles is important for protection of the mammary gland. Neutrophils from proven bulls varied in their rate and capacity of phagocytosis. Coffelations between neutrophil function and production traits were ne gative and small. In vitro analysis of neutrophil function provides an other tool for the study of natural mastitis resistance.