Neutrophil extracellular trap formation by bovine neutrophils is not inhibited by milk.
Neutrophils are the first line of defense in a mammary gland infection. However, the process of neutrophil transmigration across a membrane and ingestion of fat and/or casein when incubated in milk have been shown to inhibit bacterial phagocytosis and oxidative burst functions. Recently, a killing mechanism has been described whereby stimulated neutrophils release nuclear and granule material in fibrous webs that physically trap and kill bacteria. We demonstrate that these neutrophil extracellular traps are also produced by bovine blood neutrophils stimulated with PMA/ionomycin. Importantly, neutrophil extracellular traps can be formed when neutrophils have been incubated for up to 6h in milk prior to stimulation. This contrasts milk's rapid inhibition of bacterial phagocytosis and oxidative burst functions in the neutrophil. Furthermore, stimulation of neutrophils with bacteria common to mammary gland infections leads to neutrophil extracellular traps being formed in milk. Some bacteria tested stimulated enhanced formation of neutrophil extracellular traps in milk compared to culture media. Therefore, being unaffected by incubation in milk may indicate an important role for neutrophil extracellular traps in defense against mastitis.
Lippolis
John D
JD
Periparturient Diseases of Cattle Research Unit, National Animal Disease Center, Ames, IA 50010, USA. jlippolis@nadc.ars.usda.gov
Reinhardt
Timothy A
TA
Goff
Jesse P
JP
Horst
Ronald L
RL
D000818:Animals; D001419:Bacteria / Q000276:immunology; D002417:Cattle / Q000097:blood / Q000276:immunology*; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry; D007113:Immunity, Innate / Q000276:immunology; D015759:Ionomycin / Q000276:immunology; D008856:Microscopy, Fluorescence / Q000662:veterinary; D008892:Milk / Q000276:immunology*; D018375:Neutrophil Activation / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D009930:Organic Chemicals / Q000737:chemistry; D013755:Tetradecanoylphorbol Acetate / Q000276:immunology
D005456:Fluorescent Dyes; D009930:Organic Chemicals; C416802:SYTOX Orange dye; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate