Submitted to: European Cost
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/1999
Publication Date: N/A
Technical Abstract: Neutrophil polymorphonulear leukocytes (PMN) and macrophages are the major phagocytic cells within the udder. PMN are capable of phagocytosing a wide variety of particles (microorganisms, milk fat globules, casein). Studies of PMN function indicate that milk fat globules and casein are significant deterrents to phagocytosis and destruction of mastitis pathogens by PMN in milk. These deterrents could be a major factor in establishment of intramammary infections by invading mastitis pathogens. Milking causes directed migration of healthy PMN into the mammary gland and removal of PMN whose functions were compromised by milk components. Further observations on PMN function indicate that considerable variation exists among cows in the ability of PMN to phagocytose and kill bacteria and in the ability to support those PMN functions. In uninfected mammary glands, macrophages are the predominate cells. They act as sentinels to invading mastitis causing pathogens. Once the invaders are detected, macrophages release chemical messengers called chemoattractants that cause the directed migration of PMN into the infection site. Once there, PMN phagocytose and destroy the invading pathogens. Specific ligands on the neutrophil surface are required for recognition of bacteria and phagocytosis. However, during phagocytosis PMN release toxic chemicals that also destroy milk secretory cells. Resident and newly migrated macrophages help reduce the damage to the epithelium by phagocytosing PMN through a process called apoptosis. Advances in molecular biology are making available new therapeutics for the treatment and prevention of mastitis in dairy cows.