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Title: IN VIVO AND IN VITRO EVIDENCE OF AN L-SELECTIN AND MAC-1 RESERVOIR IN BOVINE POLYMORPHONUCLEAR LEUKOCYTES

Author
item DIEZ-FRAILE, ARACELI - U GHENT BELGIUM
item MEYER, EVELYNE - U GHENT BELGIUM
item TOMITA, GRANT - LANGSTON U OKLAHOMA
item Paape, Max
item BURVENICH, CHRISTIAN - U GHENT BELGIUM

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2002
Publication Date: 2/1/2003
Citation: DIEZ-FRAILE, A., MEYER, E., TOMITA, G., PAAPE, M.J., BURVENICH, C. IN VIVO AND IN VITRO EVIDENCE OF AN L-SELECTIN AND MAC-1 RESERVOIR IN BOVINE POLYMORPHONUCLEAR LEUKOCYTES. JOURNAL OF DAIRY SCIENCE. 2003.

Interpretive Summary: Migration of neutrophils from blood to tissue depend upon intercellular stores of adhesion molecules. As neutrophils travel in the blood stream along the wall of blood vessels, adhesion molecules are shed and must be replaced. If this replacement fails the neutrophil cannot migrate into tissue, placing the host at a great risk to infection. One type of molecule, L-selectin, allows the neutrophil to walk along the blood vessel wall. Once invading pathogens in tissue are detected by the neutrophil another type of adhesion molecule called Mac-1 is upregulated to the surface from the intracellular pool, allowing the neutrophil to quickly migrate into tissue and destroy the invaders. Following neutrophil activation, surface expression of adhesion molecules like L-selectin rapidly decrease while Mac-1 increases. By using flow cytometry it was possible for scientists at the USDA to detect for the first time the existence of storage pools of L-selectin and Mac-1 in bovine neutrophils. This intracellular pool is important to replace the shed molecules. Importantly, the scientists were able to show that the intracellular store is rapidly depleted upon activation of neutrophils. Once activation occurs, like during calving, it will take several days for the intracellular pool to be restored putting animals at a great risk to infection. Indeed, the period after calving is a time of increased susceptibility to intramammary infection in dairy cows. Scientists are now trying to find a way to prevent loss of the intracellular pool during calving.

Technical Abstract: The expression of L-selectin and Mac-1 adhesion molecules on bovine neutrophils was studied during induced coliform mastitis in six dairy cows by flow cytometry. A decrease in L-selectin and an increase in Mac-1 expression were observed upon intramammary challenge with Escherichia coli. Using cellular permeabilization with saponin, a large intracellular pool of Mac- 1 and L-selectin was detected in neutrophils. Upon activation of neutrophils with platelet activating factor (PAF) the intracellular pool of L-selectin decreased. No decrease was observed for Mac-1. It was found that actin filaments and microtubules partly regulate surface expression of adhesion molecules on bovine neutrophils. Detergent permeabilization studies in bovine neutrophils indicate that L-selectin and Mac-1 are stored in latent pools, which can be selectively mobilized upon stimulation.