EFFECT OF HYPERBARIC-OXYGEN ON TISSUE DISTRIBUTION OF MONONUCLEAR CELL SUBSETS IN THE RAT

In a previous study we found a significant temporary decrease in the r atio of CD4/CD8 (helper, inducer/suppressor, cytotoxic) T lymphocytes in the peripheral blood of healthy human volunteers after exposure to a single commonly used profile of hyperbaric oxygen (HBO). The transie nt nature of the changes suggested redistribution of T-cell subsets. T he purpose of the present study was to verify such a redistribution an d to locate possible target organs in an animal model. A single exposu re of rats to HBO (0.28 MPa) induced a highly significant rapid decrea se in the CD4/CD8 ratio in peripheral blood count (P < 0.0001), confir ming our previous findings in humans. HBO also induced a significant i ncrease in the CD4/CD8 ratio in the lungs and lymph nodes (P < 0.001) and a significant decrease in the ratio in the spleen (P < 0.01). Furt hermore, exposure to HBO induced a significant increase in T cells bea ring surface interleukin-2 receptors in the blood, spleen, lungs, and lymph glands (P < 0.001) and a significant decrease in T cells express ing alpha beta-receptors in the lungs (P < 0.001) and lymph glands (P < 0.05). Our findings suggest rapid T-cell activation after a brief ex posure to HBO, with shifts of CD4 and CD8 subsets and variations in T- cell receptor type. These rapid changes in the parameters of cell-medi ated immunity may represent the activation of protective mechanisms ag ainst the toxic effect of oxygen or the early stages of pulmonary oxyg en toxicity.