Expression of Endothelial Selectin Ligands on Leukocytes Following Repeated Dives in SCUBA Divers

Background and Purpose: Leukocyte cell surface adhesion molecule CD11b, decorated with CD15s, plays a critical role in the regulation of b2 integrin function during neutrophile endothelial transmigration. Hyperbaric oxygenation reduces neutrophil-endothelial cell adhesion, which is mediated by Mac-1 (CD11b/CD18) B2-integrin. Materials and Methods: This study investigated the expression of CD15 and CD15s, on leukocytes following repeated trimix dives in two series: in the first series 7 divers performed 6 consecutive dives from 55-80 m, while in the second series 7 divers performed 3 consecutive dives from 63-65 m. A more intense dive profile was used in the second series, as can be seen from the longer total dive time. Five divers took part in each of the two series. CD15 and CD15s were determined before and after the 1st and the last dive. Results and Conclusions: Leukocyte subpopulations were not elevated after either the first or last dives in series I. Only CD15+CD15s+ granulocytes were significantly decreased after the 1st dive. In the second series the monocyte proportion was increased and lymphocytes decreased within the total leukocyte population, while CD15s+ monocytes and CD14+CD15s+ granulocytes were elevated after the 1st dive. CD15+CD14+ granulocytes were decreased after the 1st and the last dive in the second series, while CD15s+ granulocytes were decreased only after the last dive in the second series. The current findings of decreased endothelial selectin ligand CD15s expression on CD15+ granulocytes after certain dives point to the role of this subpopulation in the endothelial damage prevention.