LEUKOCYTE L-SELECTIN IS UP-REGULATED AFTER MECHANICAL TRAUMA IN ADULTS

Background: Infection and multiple organ failure remain the principal causes of late mortality after trauma despite advances in the resuscit ation of injured patients. Because a better understanding of postinjur y leukocyte trafficking is essential to the development of possible th erapeutic measures aimed at preventing these complications, we have pe rformed a study of one factor in the early posttrauma endothelial adhe sion behavior of monocytes, lymphocytes, and neutrophils: their cell s urface expression of L-selectin (CD62L). We have also studied the plas ma levels of soluble L-selectin in these patients. Methods: Two venous blood samples were taken from each of 41 trauma patients at median ti mes of 1 and 20 hours after injury, The study group included 16 patien ts with major (Injury Severity Score (ISS) greater than or equal to 16 ), 17 with moderate (ISS = 9-15), and 8 with minor (ISS < 9) trauma, C ell surface L-selectin was measured on leukocyte subsets by staining w ith specific fluorescent-labeled monoclonal antibodies to CD62L and us ing flow cytometry. Both the percentage of cells expressing the molecu le and the mean channel fluorescence were measured. Levels of soluble L-selectin were measured in the plasma, sampled concurrently, by enzym e-linked immunosorbent assay. Results: Monocytes, lymphocytes, and neu trophils all showed an early increase in cell surface L-selectin expre ssion as measured by mean channel fluorescence (p < 0.0001, p < 0.001, and p < 0.0001, respectively), and this persisted in later samples ta ken at a median 20 hours after injury (p < 0.0001, p < 0.0001, and p < 0.01), Only monocytes showed an increased percentage of cells express ing the molecule in the early phase (p < 0.02), and this remained in t he later phase (p < 0.001). Monocytes also showed a further significan t increase in mean channel fluorescence (p < 0.02) between the two per iods. No significant changes in levels of plasma soluble L-selectin we re found at either stage. Conclusion: An increase in the expression of L-selectin on each of three leukocyte populations has been demonstrat ed in the early phase after trauma, This would tend to promote rolling behavior of leukocytes and increase their contact with the vascular e ndothelium, There were marked differences in the later responses of th e three populations, which may represent differential control of their behavior.