|VAN OOSTVELDT, K|
Submitted to: Plugers Archives
Publication Type: Proceedings
Publication Acceptance Date: 5/21/2000
Publication Date: N/A
Technical Abstract: Apoptosis regulates the clearance of neutrophils from the inflammatory site without inducing additional inflammatory reactions. In the current study, the percentage of apoptotic neutrophils was determined in blood samples taken from cows with E. coli mastitis or endotoxin induced mastitis following an in vitro incubation period of 3 h. A flow cytometric technique was used to detect apoptosis and necrosis of bovine neutrophils using fluoriscein isothiocyanate labeled annexin-V in combination with propidium iodide. On average, no significant changes were detected during endotoxin challenge. However, E. coli challenge increased the level of apoptotic neutrophils in blood and a peak was observed 18 h after challenge (P<0.01). At this time, 20% of the neutrophils were apoptotic compared to control levels (5%). During E. coli and endotoxin challenge, studies have shown that spontaneous respiratory burst activity was increased. Because no accelerated apoptosis was detected during endotoxin mastitis, we sugges that acceleration of neutrophil apoptosis during mastitis caused by increased respiratory burst is minimal. Other studies have shown that the cytokine TNF-alpha (TNFa) which is absorbed in the plasma during an inflammatory reaction, is less absorbed during endotoxin induced mastitis compared to E. coli induced mastitis. It is also know that TNFa induces apoptosis in neutrophils. Therefore, it is thought that the absorption of TNFa in plasma might be responsible for the accelerated apoptosis during E. coli mastitis whereas during endotoxin mastitis the concentration of TNFa in plasma might not be high enough to induce accelerated apoptosis of neutrophils.