Differential sensitivities to hyperbaric oxygen of lymphocyte subpopulations of normal and autoimmune mice

We studied the effect of exposure to hyperbaric oxygen (HBO): 2.8 atm absolute 100% oxygen for 4 h daily over 3-7 days, on the immune system of normal (BALB/c and MRL- +/+) and autoimmune MRL-lpr/lpr) mice. In HBO exposed BALB/c mice, we observed a remarkable decrease in the cell population of the spleen and thymus. We found that the sensitivity to HBO varied among subpopulations of lymphocytes. For example, CD4+ CD8+ double positive cells in the thymus and B220+ B cells in the spleen were more sensitive than CD4+ or CD8+ single positive T cells in the thymus, and Thy-1+ T cells in the spleen, respectively. Accordingly, despite the decrease in total cell number in the spleen, the proliferative response of T cells from the spleen to Con A was not impaired in the HBO exposed mice. Exposure of MRL-lpr/lpr mice to HBO caused a marked reduction of weight and cell population of the otherwise enlarged spleen and lymph nodes, and amongst others of percentages of B220+Thy-1+ double positive abnormal cells. These results suggest the HBO therapy may be applicable for the treatment of some autoimmune diseases.