The recall alloresponse following retransplantation is more intense compared with the T cell memory-transfer model

The presence of alloreactive memory T cells in recipient is a critical handicap to achieving transplantation tolerance. To make a mouse model that can as closely as possible mimic the presensitized transplant patient is important for research on this subject. Thus, we developed a novel retransplant model and compared the alloresponse in this model with that in the memory T cells-transfer model (transfer control). Mean survival time of allograft was compared between 3 groups, including blank transplant control, memory transfer control and retransplant groups. Cellular rejection activity in allografts was evaluated via HE staining of cardiac graft section. Proliferation and differentiation of the alloreactive effector T cells were assayed by in vitro mixed lymphocyte reaction and flow cytometry, respectively. Real-time quantitive RT-PCR was used to assess gene expression of cytokines and surum IFN-gamma was measured via ELISA. It showed that the median survival time of allograft in retransplant recipients was significantly shortened compared to that of transfer control, and it was the same in rejection score of graft. Moreover, proliferation and differentiation of the alloreactive effector T cells were more intensive in retransplant recipients than that in transfer control, which was confirmed by in vitro mixed lymphocyte reaction and by flow cytometry of the splenocytes for detecting CD44highCD62L- memory/effector phenotype cells. Furthermore, activation of CD4+ memory T cells is reflected by high level of surum IFN-gamma and the intensive gene expression of IFN-gamma and IL-2 at cardiac allograft in retransplant recipients. Collectively, the recall alloresponse in retransplantation is more intensive than that in a memory-transfer setting, and this retransplant model is closer to the clinic situation than the memory-transfer model in rodents.