Objective  To evaluate the effect of extracorporeal photopheresis upon the expression levels of interleukin (IL)-12p70 and T helper cell (Th) 1/Th2-like cytokines in splenic lymphocytes of mouse models undergoing skin transplantation.

  Methods  The C57BL/6 mice were used as the donors and BALB/c mice as the recipients to establish mouse models with skin allograft. The splenic lymphocytes in the C57BL/6 and BALB/c mice (CSP and BSP) were isolated and treated with 8-methoxypsoralen combined long-wave ultraviolet (PUVA-SP). According to the components of intravenous infusion into the recipients, all experimental animals were randomly divided into the PUVA-BSP, PUVA-CSP, BSP, CSP and phosphate buffer solution (PBS) control groups (n=12 for each group). The mice were injected with PUVA-BSP, PUVA-CSP, BSP, CSP or PBS via the caudal vein at preoperative 7 d, upon the day of surgery and at postoperative 7 d, respectively. The apoptosis of the splenic lymphocytes was observed after PUVA treatment. The expression levels of IL-12p70 and Th1/Th2-like cytokines in the peripheral blood of the recipients were quantitatively measured.

  Results  After the skin transplantation, the expression levels of IL-12p70 in the peripheral blood of mice in the PUVA-BSP and PUVA-CSP groups were significantly down-regulated compared with those in the BSP, CSP and PBS control groups (all P < 0.01). In the PUVA-BSP and PUVA-CSP groups, the expression levels of Th1-like cytokine IL-2, interferon (IFN)-γ were dramatically lower than those in the BSP, CSP and PBS control groups (all P < 0.01). The expression levels of Th2-like cytokine IL-10 in the PUVA-BSP and PUVA-CSP groups were significantly up-regulated compared with those in the BSP, CSP and PBS control groups (all P < 0.01).

  Conclusions  Infusion of PUVA-SP at a sufficient dose can induce the low expression level of IL-12p70 and drive the incidence of Th2 immune deviation in the recipient BALB/c mice.