Apoptosis of bovine neutrophils during mastitis experimentally induced with Escherichia coli or endotoxin.
OBJECTIVE
To determine whether apoptosis of neutrophils was accelerated during mastits experimentally induced by use of Escherichia coli or E coli endotoxin and whether differences were apparent in the response to E coli or endotoxin.


METHODS
11 healthy lactating Holstein cows.


METHODS
Blood samples were collected from cows at various intervals after intramammary inoculation with E coli or endotoxin. Percentage of apoptotic neutrophils detected after in vitro incubation for 3 hours was determined. Fluorescein isothiocyanate-labeled annexin-V in combination with propidium iodide was used to distinguish apoptosis and necrosis of neutrophils. Total and differential circulating leukocyte counts and rectal temperature were determined at the time of collection of blood samples. Milk yield and milk somatic cell counts were determined at the time of milking.


RESULTS
Inoculation of endotoxin did not accelerate in vitro induction of neutrophil apoptosis. However, inoculation of E coli increased the percentage of apoptotic neutrophils. At 18 hours after inoculation, 20% of the neutrophils were apoptotic, compared with 5% before inoculation. Milk somatic cell count and rectal temperature increased, milk production and total leukocyte count decreased, and percentage of immature neutrophils increased after inoculation with E coli or endotoxin. However, kinetics of the responses were more rapid, more severe, and of shorter duration during endotoxin-induced mastitis.


CONCLUSIONS
In vitro induction of apoptosis of neutrophils was accelerated only during E coli-induced mastitis and not during endotoxin-induced mastitis. Endotoxin inoculation as a model for studying coliform mastitis in dairy cows should be viewed with caution.
Van Oostveldt
Kaat
K
University of Ghent, Faculty of Veterinary Medicine, Department of Physiology, Biochemistry and Biometrics, Merelbeke, Belgium.
Tomita
Grant M
GM
Paape
Max J
MJ
Capuco
Anthony V
AV
Burvenich
Christian
C
D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D001831:Body Temperature; D002417:Cattle; D004731:Endotoxins / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology* / Q000382:microbiology; D005260:Female; D007774:Lactation; D007958:Leukocyte Count / Q000662:veterinary; D008414:Mastitis, Bovine / Q000209:etiology / Q000276:immunology* / Q000382:microbiology; D008892:Milk / Q000378:metabolism / Q000382:microbiology; D009504:Neutrophils / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D011897:Random Allocation
D004731:Endotoxins; C044101:endotoxin, Escherichia coli