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A possible role for L-selectin in the release of polymorphonuclear leukocytes from bone marrow
S F van Eeden1, R Miyagashima, L Haley
1Pulmonary Research Laboratory, University of British Columbia, St. Paul's Hospital, Vancouver, Canada.
Abstract:
Previous studies from our laboratory have shown that the expression of L-selectin on polymorphonuclear leukocytes (PMN) is higher in the bone marrow than in peripheral blood. The present study was designed to determine the location of this L-selectin loss as the PMN pass from the hematopoietic tissue into venous sinusoids of the bone marrow. Bone marrow and peripheral blood samples were collected at the beginning, during, and just after five normothermic cardiopulmonary bypass procedures in which there was active marrow release and compared with five hypothermic procedures in which marrow release was suppressed by lowering body temperature to 27 degrees C. L-selectin expression was measured on PMN in the hematopoietic tissue and venous sinusoids in the bone marrow using quantitative histology and immunocytochemistry. At baseline there was more L-selectin on PMN in the bone marrow hematopoietic tissue than in the sinusoids (24.7 +/- 3.5 vs. 10.3 +/- 2.5%, P < 0.004). Bone marrow release during normothermic cardiopulmonary bypass procedure was associated with a rise in peripheral blood band cells (0.18 +/- 0.7 vs. 2.98 +/- 0.56 x 10(9)/l, P < 0.01) and a further reduction of L-selectin expression on PMN in the sinusoids (P < 0.03). Hypothermia (27 degrees C) prevented both the rise in peripheral blood band cells and the reduction in L-selectin on PMN in the sinusoids. In vitro studies showed that lowering the temperature had a similar effect on shedding of L-selectin from PMN. We conclude that PMN shed L-selectin as they move from the hematopoietic compartment into the venous sinusoids of the bone marrow and postulate that this could control the release of PMN from the marrow.
Insights
Polymorphonuclear leukocytes (PMN) shed L-selectin as they leave bone marrow, a process inhibited by hypothermia. This shedding may regulate PMN release into circulation.
Area of Science:
- Hematology
- Immunology
- Cell Biology
Background:
- L-selectin expression is higher on polymorphonuclear leukocytes (PMN) in bone marrow compared to peripheral blood.
- The precise location and mechanism of L-selectin loss during PMN egress from bone marrow remain unclear.
Purpose of the Study:
- To determine where L-selectin is lost as PMN transition from bone marrow hematopoietic tissue to venous sinusoids.
- To investigate the role of temperature in L-selectin shedding and PMN release during cardiopulmonary bypass.
Main Methods:
- Quantitative histology and immunocytochemistry were used to measure L-selectin expression on bone marrow PMN.
- Samples were collected from patients undergoing normothermic and hypothermic cardiopulmonary bypass.
- In vitro studies assessed the effect of temperature on L-selectin shedding.
Main Results:
- Baseline L-selectin expression was significantly higher in bone marrow hematopoietic tissue than in sinusoids.
- Normothermic bypass increased peripheral blood band cells and reduced L-selectin on sinusoidal PMN.
- Hypothermia (27°C) prevented both the increase in band cells and the reduction in L-selectin.
Conclusions:
- PMN shed L-selectin during their movement from bone marrow hematopoietic tissue to venous sinusoids.
- Temperature significantly influences L-selectin shedding and PMN release from the bone marrow.
- L-selectin shedding is a potential mechanism controlling PMN release from the marrow.