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Polymorphonuclear leukocytes L-selectin expression decreases as they age in circulation
S F Van Eeden1, S Bicknell, B A Walker
1University of British Columbia, Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, Canada.
The American Journal of Physiology
|January 1, 1997
Summary
Polymorphonuclear leukocytes (PMN) lose L-selectin as they age in circulation. This study confirms that L-selectin expression decreases on PMN over time, supporting their aging process in the bloodstream.
Area of Science:
- Immunology
- Hematology
- Cell Biology
Background:
- Previous findings indicated increased L-selectin on circulating polymorphonuclear leukocytes (PMN) during bone marrow release.
- This suggests a potential inverse relationship between PMN age and L-selectin expression in circulation.
Purpose of the Study:
- To investigate the hypothesis that L-selectin expression diminishes on PMN as they age within the circulation.
- To quantify the reduction in L-selectin levels on PMN over a 24-hour period in vitro and in vivo.
Main Methods:
- In vitro flow cytometry to assess PMN L-selectin levels after 24-hour incubation at 37°C.
- In vivo studies using 5'-bromo-2-deoxyuridine (BrdU) labeled rabbit PMN infused into recipient rabbits.
- Double immunolabeling technique to track L-selectin-negative PMN-BrdU in circulation over 24 hours.
Main Results:
- In vitro incubation led to a significant decrease in PMN L-selectin expression to 14.6 +/- 2.3% of baseline.
- In vivo, the fraction of L-selectin-negative PMN-BrdU increased significantly over 24 hours (P < 0.001).
- Chymotrypsin treatment to remove L-selectin did not alter PMN clearance rates from circulation.
Conclusions:
- PMN continuously lose L-selectin from their surface throughout their lifespan in circulation.
- This supports the hypothesis that L-selectin expression decreases on PMN as they age.
- The loss of L-selectin is a characteristic feature of PMN aging in the bloodstream.