Effect of permissive hypercapnia on CD4⁺ and CD8⁺ T cells of rats with acute rejection after lung transplantation

  Objective  To investigate the effect of permissive hypercapnia on CD4⁺ and CD8⁺ T cells of rats with acute rejection after lung transplantation.

  Methods  Twenty-four male Wistar rats and 12 male SD rats were paired and randomly divided into 3 groups (6 pairs per group). SD and Wistar rats were used as the donors and recipients in the control group and treatment group, respectively, and Wistar rats were used as the donors and recipients in the allograft group. Acute rejection rat model of orthotopic left lung transplantation was established by Cuff method. The treatment group was treated with 50% oxygen and 8% carbon dioxide after reperfusion, but only 50% oxygen for the control group and allograft group after reperfusion. Expressions of CD4⁺ and CD8⁺T cells in transplanted lung tissue were detected with immunohistochemical (IHC) method on 7 d after the operation. Proportion of CD4⁺ and CD8⁺T cells in peripheral blood was detected with flow cytometry. Furthermore, levels of interleukin (IL)-2 and interferon (IFN)-γ in peripheral blood were detected with enzyme-linked immune absorbent assay (ELISA).

  Results  The IHC results showed that, compared with the control group, the expression of CD8⁺T cells in transplant lung tissue of rats decreased significantly in both the treatment group and allograft group. The results of flow cytometry showed that compared with the control group, the proportion of CD8⁺T cells decreased significantly in both treatment group and allograft group (both P < 0.05). ELISA results showed that, compared with the control group, levels of IL-2 and IFN-γ decreased significantly in both treatment group and allograft group (both P < 0.05).

  Conclusions  Permissive hypercapnia can inhibit the acute rejection after lung transplantation through inhibiting the proliferation of CD8⁺T cells and release of inflammatory cytokines in CD4⁺ T cells.