title: Polymorphonuclear leukocytes L-selectin expression decreases as they age in circulation.
abstract: We recently reported that L-selectin expression increases on circulating polymorphonuclear leukocytes (PMN) during active bone marrow release, which suggests that older cells in the circulation have lower levels of L-selectin than those recently released from the bone marrow. The present study was designed to test the hypothesis that L-selectin expression reduces on PMN as they age in the circulation. In vitro studies using flow cytometry showed that PMN L-selectin decreased to 14.6 +/- 2.3% of baseline during a 24-h incubation at 37 degrees C. To test this hypothesis in vivo, rabbit PMN, labeled in vivo with 5'-bromo-2-deoxyuridine (PMN-brdU) in donor animals, were infused into recipient rabbits as whole blood (n = 5) and followed over 24 h in the circulation with a double immunolabeling technique. These results showed that the fraction of the L-selectin-negative PMN-BrdU in the circulation increased with time (P < 0.001), and nearly all of the PMNBrdU in the circulation were L-selectin negative after 24 h. Removal of L-selectin from the surface of PMN-BrdU with chymotrypsin before infusion did not change their rate of removal from the circulation (half-life or t 1/2 262 vs. 296 min, P = NS). We conclude that there is a continuous loss of L-selectin from PMN during their life span in the circulation, which supports the hypothesis that L-selectin expression decreases on PMN as they age.
authors.affiliation: University of British Columbia, Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, Canada.
authors.forename: S F
authors.initials: SF
authors.lastname: Van Eeden
authors.forename: S
authors.initials: S
authors.lastname: Bicknell
authors.forename: B A
authors.initials: BA
authors.lastname: Walker
authors.forename: J C
authors.initials: JC
authors.lastname: Hogg
mesh_terms: D000818:Animals; D001773:Blood Cells / Q000378:metabolism* / Q000502:physiology*; D001973:Bromodeoxyuridine; D016922:Cellular Senescence; D002918:Chymotrypsin / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D019041:L-Selectin / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D009504:Neutrophils / Q000378:metabolism*; D011817:Rabbits; D013997:Time Factors
chemical_list: D019041:L-Selectin; D002918:Chymotrypsin; D001973:Bromodeoxyuridine