Functional Analysis of Alloreactive Memory CD4+ T Cells Derived from Skin Transplantation Recipient and Naïve CD4+ T Cells Derived from Untreated Mice

Targeted regulation of lymphocytic ER stress response with an overall immunosuppression to alleviate allograft rejection

Transplantation is the most effective, and sometimes the only resort for end-stage organ failure. However, allogeneic graft suffers greatly from lymphocyte-mediated immunorejection, which bears close relationship with a hyperactivation of endoplasmic reticulum (ER) stress response in host lymphocytes, especially in CD8⁺ T cells (T-8). Therefore, regulating lymphocytic ER unfolded protein response (UPR) might be a potential therapeutic breakthrough in alleviating graft rejection. Here, ER-targetable liposome is prepared via the surface modification of ER-targeting peptide (Pardaxin), which efficiently loads and directly delivers small molecule inhibitor of UPR sensor IRE1α into the ER of lymphocytes, inducing a systemic immunosuppression that facilitates tumorigenesis and metastasis in the tumor inoculation challenge in vivo. And in vitro, a stage-differential dependency of IRE1α in the phase transition of T-8 is identified. Specifically, inhibiting IRE1α at the early responding stages of T-8, especially at the activation phase, results in a shrunk proliferation, impaired effector function, and limited memory commitment, which might contribute centrally to the induced overall immunosuppression. Based on this, a classical acute rejection model, murine full-thickness trunk skin allograft that primary arises from the hyperactivity of T-lymphocyte, is used. Results suggest that lymphocytic IRE1α inactivation attenuates transplant rejection and prolongs graft survival, with a limited effector function and memory commitment of host T-8. Moreover, an even higher immunosuppressive effect is obtained when IRE1α inhibition is used in combination with immunosuppressant tacrolimus (FK506), which might owe to a synergistic regulation of inflammatory transcription factors. These findings provide a deeper insight into the biological polarization and stress response of lymphocytes, which might guide the future development of allogeneic transplantation.

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.

The roles of sepsis-induced myeloid derived suppressor cells in mice corneal, skin and combined transplantation

PURPOSE

To explore the effects of adoptive transferring sepsis induced myeloid-derived suppressor cells (iMDSCs) in mice corneal, skin, and combined corneal-skin survival.

METHODS

Allogeneic full-thickness corneal transplantation, fully mismatched skin transplantation, and corneal-skin combined transplantation (donor C57BL/6 to recipient Balb/c mice) were performed. Sepsis-induced infectious-MDSCs (iMDSCs), were purified from bone marrow of cecal ligated and punctured (CLP) Balb/c mice. Recipient-derived iMDSCs were adoptively transferred into different recipient groups by retro-orbital injection after surgeries. Corneal and skin grafts were examined and photographed routinely for a period of 45days. Histopathology was performed to evaluate corneal-graft inflammation. Bone marrow and/or corneal grafts in each group were harvested from executed recipients on postoperative days 15, 25, 35. Corneal cells and bone marrow cells were stained with CD11b-PE and Gr1-FITC, analyzed by FACS.

RESULTS

iMDSCs were able to significantly prolong allograft survival in both corneal and corneal-skin combined transplant groups. A substantial expansion of MDSCs was observed in recipients' bone marrow, particularly in combined groups at an early stage postoperatively, and accordingly the concentration of MDSCs in corneal grafts increased significantly in adoptive transferred groups.

CONCLUSIONS

Sepsis-induced MDSCs may suggest a novel cellular therapeutic approach for preventing various types of allograft rejection.

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.