The Primary Study Of γδT Cell Functions In Skin Allograft Rejection

BackgroundHow to control the strong immunological rejection of skin allograft is a big challenge for severe burnt wound management. In classical immunological theory, Langerhans cells played a key role in initiating the skin allograft rejection. However, the survival time of skin allograft in LCs KO mice was not found to be significantly prolonged, compared with the wild-type mice, which indicated that there were still some other cells involved in initiating skin allograft rejection. Another important constituent of skin immune microenvironment is γδ T cell. Recent studies had demonstrated that γδ T cell might be essential for wound healing, tumor, infection, and autoimmune diseases. Our previous work showed that, the survival time of skin allograft in TCR δ-/- mice was significantly prolonged, compared to the wild-type mice,which suggested that γδ T cells played an important role in skin allograft rejection. Furthermore, γδ T cells could secrete a lot of cytokines. The subtypes of γδ T cells might be: 1. the Vγ3 cells(DETCs) distributed in the epidermal tissues; 2. the Vγ4 T cells distributed in the dermal tissues; 3. the Vγ4 T cells distributed in the peripheral circulation. So far, the most important subtype of γδ T cells for the skin allograft rejection and the underlying mechanism were not clear. Throw light on these issues will not only enable us to further understand the skin allograft rejection, but also be helpful for a better control of the skin allograft rejection.ObjectiveThe aim of the present study focused on investigating the involvement and the underlying mechanism of γδ T cells in accelerating the skin allograft rejection.Methods1. The survival time of skin allograft of the wild-type mice and TCR δ-/- mice was compared by establishing the skin allograft model of mice which had small differences in MHC molecules(male to female).2. The morphology of DETCs was observed by immunofluorescence. The phenotypes and the secreted cytokines of DETCs were analyzed by Flow Cytometry. Furthermore, the differentiation of na?ve CD4+ T cells, which co-cultured with the DETC sin vitro, was identified by Flow Cytometry.3. The survival time of skin allograft of the wild-type mice and Vγ4 depletion mice, was compared by establishing the skin allograft model of mice which had small differences in MHC molecules(male to female). Moreover, the epidermal cells of skin allograft were separated at 5th day after skin transplantation to identify the infiltration of Vγ4 T cells by Flow Cytometry. And the results were compared with that in the normal skin. Meanwhile, the expressions of IL-17, IL-23 and IL-1β in epidermis were detected by Western blot.Results1. The mean survival time of skin allograft in TCR δ-/-mice was 22.30 days, while the mean survival time of skin allograft in wild-type was 10.60 days. The survival time of skin allograft in TCR δ-/- mice was significantly prolonged compared with the wild-type mice.( Log rank P <0.001)2. DETCs were found to show the dendritic shape of APC in morphology, and they could secrete a certain level of IFN-γ and IL-17 upon stimulation, which were determined to be able to induce the Th1 differentiation of na?ve CD4+ T cells in vitro.3. The mean survival time of skin allograft in Vγ4 depletion mice was 49.08 days, while the mean survival time of skin allograft in wild-type was 11.00 days. The survival time of skin allograft in Vγ4 depletion mice was significantly prolonged compared with the wild-type mice.( Log rank P<0.001)4. The infiltration of Vγ4 T cells in the skin allograft were found to be significantly increased at 5th day after transplantation compared with the normal skin(0.86% to 6.08%). And the DETCs were found to be decreased at the same time(2.38% to 0.78%). The expressions of IL-17, IL-23 and IL-1β in epidermis were detected to be enhanced in the skin allograft.ConclusionThis study preliminarily demonstrated that the γδ T cells participated in accelerating the skin allograft rejection. And the different subtypes had the different roles in the skin allograft rejection. The DETCs which showed the basic characteristics of APCs might function as the key DCs in the skin allograft immune rejection. The Vγ4 γδ T cells could provide an early source of IL-17 to enhance the skin allograft rejection. Above all, γδ T cells were important in the skin immune microenvironment and played a key role in skin transplantation immune rejection.