EFFECT OF A SINGLE EXPOSURE TO HYPERBARIC-OXYGEN ON BLOOD MONONUCLEAR-CELLS IN HUMAN-SUBJECTS

We studied the effect of a single exposure to a therapeutic profile of hyperbaric oxygen on blood mononuclear cell subset. Twenty healthy vo lunteers were exposed to 0.28 MPa for 90 min. Thirteen breathed pure o xygen and seven were control subjects exposed to compressed air at the same pressure. Venous blood samples were drawn before HBO exposure, i mmediately on exit from the chamber, and 24 h later. Immediately after the exposure, a significant increase was observed in the percentage a nd absolute number of CD8 (suppressor/cytotoxic) T cells, with a conco mitant decrease in the CD4 (helper/inducer) T cells. These changes res ulted in a decreased CD4:CD8 ratio. A rise was also observed in the nu mber of HLA-DR antigen-bearing cells, with a transient increase in mon ocytes. There was no change in the total count and percentage of T cel ls (CD3), B cells, and NK cells. Twenty-four hours after HBO exposure there was a partial reversal of the decrease in the mean CD4:CD8 ratio , but it was still significantly lower than preexposure values. The fa st reversibility of the change in the CD4:CD8 ratio suggests specific HBO-induced shifts and sequestration of T-cell subpopulations.