Related Experiment Videos
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.
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.
Insights
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.