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Title: L-SELECTIN AND CHEMOTAXIS THROUGHOUT BONE MARROW GRANULOCYTE MATURATION IN THE BOVINE

Author
item MONFARDINI, ERICA - GHENT UNIVERSITY BELGIUM
item VAN MERRIS, VALERIE - GHENT UNIVERSITY BELGIUM
item Paape, Max
item DUCHATEAU, LUC - GHENT UNIVERSITY BELGIUM
item BURVENICH, CHRISTIAN - GHENT UNIVERSITY BELGIUM

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2004
Publication Date: 10/4/2004
Citation: Monfardini, E., Van Merris, V., Paape, M.J., Duchateau, L., Burvenich, C. 2004. L-selectin and chemotaxis throughout bone marrow granulocyte maturation in the bovine. Journal of Dairy Science. 87(10):3350-3357.

Interpretive Summary: During infection of the mammary gland of dairy cows, neutrophils are the first cells recruited. During Escherichia coli mastitis in cows, the capability of neutrophils to respond to chemotactic stimuli has been shown to relate negatively to the outcome of the disease. Large numbers of neutrophils are rapidly removed from bone marrow reserves during an acute infection. Approximately 48 hours after an E. coli intramammary infection, only 50% of the blood neutrophils are mature and the remaining cells are immature. Researchers have recently shown for the first time that immature neutrophils in the bone marrow express molecules on their surface that allows them to stick to vessel walls, and that these cells are capable of responding to chemicals that recruit neutrophils to infection sites. However, immature neutrophils are less efficient at ingesting and killing bacteria. As a result large numbers of immature neutrophils are required to eliminate intramammary infection. The large number needed may exceed the capacity of the bone marrow reserves and leave the animal more susceptible to contracting other diseases.

Technical Abstract: Polymorphonuclear neutrophilic leukocytes (PMNL) play a pivotal role during inflammation. Bone marrow (BM) reserves are depleted as cells are released into circulation for recruitment to infection sites. Expression of L-selectin on the cell membrane allows neutrophils to roll along the activated endothelium. Whereas mechanisms leading to recruitment to infection sites are well established, expression of BM adhesion molecules in cows is limited. In this study, we assessed L-selectin expression and chemotactic response to zymosan-activated serum (ZAS) in bovine BM cells and in circulating neutrophils. Isolated blood PMNL and BM cells were used from 9 dairy cows, for quantifying L-selectin expression using flow cytometry, and from 12 dairy cows for chemotaxis studies. All granulocytic maturation stages expressed L-selectin. The percentage of cells fluorescing increased significantly in BM band and mature granulocytes and reached maximal expression on circulating neutrophils. Bone marrow band and segmented cells showed the highest L-selectin density. Chemotaxis through micropore filters in response to zymosan-activated fetal bovine serum was first observed in the myelocytic and metamyelocytic stages, and it increased with maturation and release into the blood stream. From these results, we conclude that L-selectin expression varies among stages of granulocytic maturation within the BM and differs from circulating PMNL. Further, BM cells are capable of migration starting at the metamyelocytic stage, and compared with BM cells, circulating neutrophils are more chemotactively active.