The Effects of Hyperbaric Exposure on Human Peripheral Blood Mononuclear Cells, with Special Emphasis on Natural Killer Cell Cytotoxicity and Subsets

Krog, J.; Jepsen, C. F.; Tønnesen, E.; Parner, E.; Hokland, M.

Materials and methods: As an experimental physiological stress model, we examined the effects of hyperbaric exposure on peripheral blood mononuclear cells (PBMCs) obtained from venous blood drawn from eight divers during a simulated heliox saturation dive. Eight persons working in normobar atmosphere outside the pressurized chamber served as control donors. The spontaneous cytotoxicity of the PBMCs was estimated in a 4 h 51Cr‐release assay using k562 as NK‐sensitive target cells. The PBMCs were characterized, using 4‐colour flow cytometry, with special emphasis on the NK‐cell subsets. The data were statistically analysed using a multivariate regression model (Stata 8.2). P values <0.05 was considered statistically significant. Results: The estimated cytotoxicity increased significantly in both the group of divers and control donors during the dive (pdivers < 0.01 and pcontrols < 0.01). Although the cytotoxicity increased relatively more (P < 0.01) in the group of divers compared to the group of control donors between day 1 and 2. Discussion: The increased cytotoxicity of PBMC estimated in the group of divers indicate that parts of the cellular immune system are affected during the extreme physiological conditions induced during the initial phase of the presented experimental hyperbaric setup. The increase in cytotoxicity observed in the group of control donors could hypothetically reflect the stress level in persons working outside the pressurized chamber during the dive.