In vitro effects of acellular milk on the bactericidal components of caprine polymorphonuclear neutrophils.

The effects of acellular milk on the activity of the microbicidal cationic enzymes of the polymorphonuclear cells of goats were studied in an attempt to explain the phenomenon by which PMN functions fail in mastitis. Assays were undertaken on the myeloperoxidase, lysozyme and elastase activities in a polymorphonuclear cell (PMN) lysate, both in the presence and absence of acellular milk from homologous species. There was a significant decrease (p < 0.05) in the activity of lysozyme, myeloperoxidase and elastase in the presence of acellular milk. Superoxide and H2O2 production following activation of caprine PMNs by lipopolysaccharide (LPS) was significantly reduced (p < 0.05) in the presence of acellular milk. Thus, the microbicidal function of PMNs is significantly impaired in the presence of acellular milk and this may contribute to the development of mastitis in dairy animals.