Hypercapnia therapy alleviated the accumulation of T lymphocytes in the peripheral blood. Representative fluorescence-activated cell sorting scatterplots and statistical charts of CD4⁺ T cells (A), CD8⁺ T cells (B), and CD4⁺/CD8⁺ T cell ratio (C) in sham-operated, isograft, allograft, and hypercapnia groups. Difference of T cell subsets and CD4⁺/CD8⁺ T cell ratio among groups were analyzed by using one-way ANOVA followed by the Student–Newman–Keuls post hoc test. ^#P < 0.05 versus allograft group.