Role of regulated upon activation normal T-cell expressed and secreted in a model of retransplantation acute rejection mediated by alloreactive memory CD4+ T cells

Triptolide inhibits CD4+ memory T cell-mediated acute rejection and prolongs cardiac allograft survival in mice

There have been numerous investigations into the immunosuppressive effects of triptolide; however, its inhibitory effects on memory T cells remain to be elucidated. Using a cluster of differentiation (CD)4⁺ memory T-cell transfer model, the aim of the present study was to determine the inhibitory effects of triptolide on CD4⁺ memory T cell-mediated acute rejection and to determine the potential underlying mechanisms. At 4 weeks after skin transplantation, mouse cervical heart transplantation was performed following the transfer of CD4⁺ memory T cells. Mice were divided into two groups: A Control [normal saline, 30 ml/kg/day; intraperitoneal injection (ip)] and a triptolide group (triptolide, 3 mg/kg/day; ip). Graft survival, pathological examination and the corresponding International Society for Heart & Lung Transplantation (ISHLT) scores were assessed 5 days following heart transplantation, and levels of interleukin (IL)-2, interferon-γ (IFN-γ), IL-10 and transforming growth factor β1 (TGF-β1) in cardiac grafts and peripheral blood were assessed using reverse transcription-quantitative polymerase chain reaction and ELISA. The duration of cardiac graft survival in the triptolide group was significantly increased compared with the control group (14.3±0.4 vs. 5.3±0.2 days; P<0.001). Further pathological examinations revealed that the infiltration of inflammatory cells and myocardial damage in the cardiac grafts was notably reduced by triptolide, and the corresponding ISHLT scores in the triptolide group were significantly lower than those of the control group (grade 2.08±0.15 vs. 3.67±0.17; P<0.001). In addition, triptolide was able to significantly reduce IL-2 and IFN-γ secretion (P<0.01), significantly increase TGF-β1 secretion in the cardiac grafts and peripheral blood (P<0.01) and increase IL-10 secretion in the cardiac grafts. Therefore, the present study suggests that triptolide inhibits CD4⁺ memory T cell-mediated acute rejection and prolongs cardiac allograft survival in mice. This effect may be mediated by the inhibition of cytokine secretion by type 1 T helper cells and promotion of regulatory T cell proliferation.

Combination of C-X-C motif chemokine 9 and C-X-C motif chemokine 10 antibodies with FTY720 prolongs the survival of cardiac retransplantation allografts in a mouse model

The upregulation of chemokine genes and the subsequent T-lymphocyte recruitment to the graft are early events in the development of acute cardiac transplant rejection or cardiac allograft vasculopathy. In the present study, a combined immunosuppressive regimen of C-X-C motif chemokine 9 (CXCL9) antibody (Ab), CXCL10 Ab and FTY720 was used in order to reduce the infiltration of memory T lymphocytes and prolong graft survival in a retransplantation murine model. BALB/c donor hearts were transplanted heterotopically into C57BL/6 mice at day 28 after skin transplantation. The mice were divided into four groups: i) Control (normal saline), ii) CXCL9 Ab and CXCL10 Ab [150 μg; once daily (qd); intraperitoneal (ip)], iii) FTY720 (0.2 mg/day; qd; ip) and iv) combined (2 mg/kg/day; qd; ip). Measurements of the median survival time of the cardiac grafts, histological examination, reverse transcription-quantitative polymerase chain reaction analysis, enzyme-linked immunosorbent assay and a mixed lymphocyte reaction were performed. The median graft survival time of the combined group was prolonged (9.3 days) compared with that of the control group (3.5 days) (P<0.001). Histological examination revealed that the combined treatment group graft rejection pathological score was 0.50, while the control group score was 3.62 (P<0.001). In addition, the gene expression level of interleukin (IL)-2 was significantly lower and the levels of IL-10 and transforming growth factor-β (TGF-β) were significantly higher in the combined group compared with those in the control group (P<0.001). Furthermore, the serum concentration levels of IL-2 and interferon-γ (IFN-γ) were significantly lower (P<0.001) and the concentration of IL-10 was significantly higher (P<0.05) in the combined group compared with those in the control group. In the mixed lymphocyte reaction, T-cell proliferation was found to be significantly lower in the combined treatment group than that in the control group (P<0.001). In conclusion, treatment with CXCL9 Ab and CXCL10 Ab or FTY720 reduced the graft infiltration of inflammatory cells, inhibited T-cell proliferation and prolonged graft survival. The combined treatment regimen of CXCL9 Ab, CXCL10 Ab and FTY720 was found to significantly reduce the infiltration of inflammatory cells in the graft and prolong graft survival.

CXCL9 and CXCL10 accelerate acute transplant rejection mediated by alloreactive memory T cells in a mouse retransplantation model

C-X-C motif chemokine ligand (CXCL) 9 and CXCL10 play key roles in the initiation and development of acute transplant rejection. Previously, higher levels of RANTES expression and secretion were demonstrated in retransplantation or T-cell memory-transfer models. In the present study, the effect of the chemokines, CXCL9 and CXCL10, were investigated in a mouse retransplantation model. BALB/c mice were used as donors, while C57BL/6 mice were used as recipients. In the experimental groups, a heterotopic heart transplantation was performed six weeks following skin grafting. In the control groups, a heterotopic heart transplantation was performed without skin grafting. Untreated mice served as blank controls. The mean graft survival time of the heterotopic heart transplantations was 7.7 days in the experimental group (n=6), as compared with 3.25 days in the control group (n=6; P<0.001). On day three following cardiac transplantation, histological evaluation of the grafts revealed a higher International Society for Heart & Lung Transplantation grade in the experimental group as compared with the control group. In addition, gene expression and serum concentrations of CXCL9, CXCL10, interferon-γ, and interleukin-2 were markedly higher in the experimental group when compared with the control group. Differences between the levels of CXCL9 and CXCL10 in the pre- and post-transplant mice indicated that the chemokines may serve as possible biomarkers to predict acute rejection. The results of the present study demonstrated that CXCL9 and CXCL10 play a critical role in transplantation and retransplantation. High levels of these cytokines during the pre-transplant period may lead to extensive acute rejection. Thus, the observations enhance the understanding of the mechanism underlying the increased expression and secretion of CXCL9 and CXCL10 by alloreactive memory T cells.