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Title: EFFECT OF ESCHERICHIA COLI INFECTION ON L-SELECTIN AND CD18 EXPRESSION ON NEUTROPHIL DIAPEDESIS ACROSS MAMMARY EPITHELIUM IN VITRO

Author
item SMITS, ELKE - UNIV OF GHENT, BELGIUM
item BURVENICH, CHRISTIAN - UNIV OF GHENT, BELGIUM
item Guidry, Albert
item Paape, Max
item DOSOGNE, HILDE - UNIV OF GHENT, BELGIUM
item MEYER, EVELYNE - UNIV OF GHENT, BELGIUM

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Escherichia coli mastitis is second only to Staphylococcus aureus in cost to the US dairymen. E. coli mastitis is characterized by an acute influx of white blood cells (WBC) from the circulation into the gland to combat the invading organisms. When this influx is soon enough and of sufficient magnitude spontaneous cure results. WBC migration from blood into the mammary gland involves the interaction of WBC and surface adhesion molecules on cells lining the blood vessels. Initial attachment of the WBC is mediated by L-selectin on WBC. L-selecin is responsible for initial attachment of the WBC to cells lining the blood vessels. L-selectin is responsible for initial binding of circulating WBC to cells lining the blood vesels and CD18 adhesion receptors are responsible for their subsequent movement into mammary tissue. This determined the effect of an E. coli infection of the mammary gland on the expression of these receptors son WBC and their migration across a monolayer of mammary secretory cells. As the E. coli infection progressed, there was a rapid loss of L-selecin receptors from the surface of WBC and an increase in the expression CD18. Blood WBC from cows E. coli mastitis were lacking in L-selectin and failed to migrate across the mammary secretory cell monolayer. Thus indicating that WBC migration from blood to mammary tissue depends on the relative amount of L-selectin and CD18 adhesion receptors on WBC and not on the mammary secretory cells. This study provided new insight into acute inflammation and anti-inflammatory mechanisms involved in response of the bovine mammary gland to invading pathogens.

Technical Abstract: Expression of L-selectin and CD18 on diapedesis of isolated blood PMN across monolayers of cultured bovine mammary epithelial cells was determined before and during experimentally induced Escherichia coli mastitis in cows. The left udder halve of six cows was inoculated with E. E. coli strain P4, inducing an intense acute inflammatory reaction accompanied by a peak of plasma cortisol 12 h after challenge. Escherichi coli growth in the gland and subsequent inflammation was commensurate with the shedding of L-selectin an increase in expression of CD18 on circulating neutrophils. A marked decrease in diapedesis of these circulating PMN across a monolayer of mammary epithelial cells in vitro was also observed. It is consluded that the mechanism of L-selectin/CD18 activation in the circulating pool of PMN is different from that induced during margination and diapedesis of PMN through the epithelium. This study further demonstrates that shedding of L-selectin and expression of CD18 without previouis rolling of the neutrophile is not sufficient to activate diapedesis.