Title: APOPTOSIS OF BOVINE POLYMORPHONUCLEAR NEUROPHIL LEUKOCYTES FOLLOWING DIAPEDESIS THROUGH A MONOLAYER OF ENDOTHELIEL AND MAMMARY EPITHELIAL CELLS
Van Osstveldt, K - CHENT UNIV BELGIUM
Burvenich, C - GHENT UNIV BELGIUM
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 2002
Publication Date: January 1, 2003
Citation: VAN OSSTVELDT, K., PAAPE, M.J., BURVENICH, C. APOPTOSIS OF BOVINE POLYMORPHONUCLEAR NEUROPHIL LEUKOCYTES FOLLOWING DIAPEDESIS THROUGH A MONOLAYER OF ENDOTHELIEL AND MAMMARY EPITHELIAL CELLS. JOURNAL OF DAIRY SCIENCE. 2003.
Interpretive Summary: The ability to mount a rapid and effective immunological response to infection is critical in protecting the mammary gland from damage caused by invading pathogens. Rapid migration of neutrophils, a phagocytic cell that engulf and destroy invading pathogens, through the blood milk is essential for rapid resolution of the infection. In order for neutrophils to function as efficient killers of bacteria, they must arrive at the battle scene as healthy cells. Scientists in the Immunology and Disease Resistance Laboratory at the USDA in Beltsville, Maryland, developed a model consisting of live bovine mammary epithelial cells on a layer of collagen, for studying migration of neutrophils outside the body. What they discovered was that just the normal act of migration induced damage to neutrophils. Scientists call this damage "apoptosis" or programmed cell death. Further, in the absence of epithelial cells the damage to neutrophils was greatly increased. During inflammation the delicate cells lining the interior of the mammary gland are destroyed by the putrid waste and toxins released by the invading bacteria leaving the collagen layer exposed. As the onrushing neutrophils migrate through the exposed collagen their life span is reduced tipping the balance of the struggle towards the invading pathogens. In order to prevent the destruction of epithelial cells, the scientists are developing novel recombinant proteins to neutralize the deadly effects that bacterial toxins have on mammary epithelial cells.
The objective of this study was to determine the contribution of epithelial cells, endothelial cells, and collagen on apoptosis of polymorphonuclear neutrophil leukocytes (PMN) during diapedesis. In a two chamber system, PMN were allowed to migrate across either calf skin and rat tail type I collagen coated micropore membranes, arterial endothelial cell monolayer, or mammary epithelial cell monolayer on collagen coated micropore membranes. The chemoattractant C5a was added to the lower chamber. Migration through the calf skin type I collagen coated membranes resulted in 20% of the PMN to become apoptotic compared to 10% for non-migrated cells. This effect was accelerated following an additional 20 h incubation period. In contrast, migration through rat tail collagen (type I) coated membrane inserts did not induce apoptosis when compared to non-migrated PMN. Following the additional 20 h incubation period, 47% of the PMN became apoptotic compared to only 9% for non-migrated PMN (P<0.01). The percentage of apoptotic PMN in the PMN population that migrated through a collagen coated membrane insert with a monolayer of endothelial cells was lower than the percentage of apoptotic PMN seen in the PMN population that migrated through a collagen coated membrane only. Migration of PMN across a mammary epithelial cell monolayer prevents the apoptotic inducing effect of collagen.