The Role Of Dentritic Epidermal T Lymohocytes In Immune Rejection Of Skin Allograft In Mice And Its Possible Mechanism

How to prolong the survival time of the skin allograft is one of main problems in burn wound repairmen. Epidermal tissue is the part with strongest antigenicity in the skin which plays a vital role in the rejection after skin allograft. The epidermis mainly composes of kertinocytes,Langerhans cells(LCs) and dendritic epidermal T lymohocytes(DETCs).LCs is conventionally thought as the core factor triggering allogeneic skin graft rejection. LCs indeed function as an immunomodulatory, but not generally a strong immune activator. It was found in the survival of graft did not extent either when LCs knockout mouse as the donor or the recipient. That results suggested that the LCs should not directly lead to alloskin rejection. It reminds us that there may be other key cells involved in skin allograft. DETC, also name as γδT cells, is another important immune cell in skin. γδT cells appear prior to αβT cells. It is mainly localize at the small intestine, lung, genital mucosa, skin and others. ???T cells are though as the immune system’s "first defense" and they recognize a variety of pathogens common antigens with a non-MHC restricted manner. There are some studies show that DETCs can promote skin graft rejection. γδ T cells from human or mouse peripheral blood could be activated simultaneously expressions high levels of costimulatory molecules, such as CD80 / CD86 and MHCII molecules, etc.. Moreover, γδT cells can directly activate na?ve CD4+ T cells presented with peptide antigen. From this point, γδT cells exhibit as one kind of professional antigen presenting cells(APC). Our previous study showed that γδT cells in the peripheral circulation could spontaneously express IFN-γ but not TGFβ. And it was found that donor’s DETC was able to enter lymph nodes through the lymphatic drainage after allogeneic skin graft. And it was found that DETC is involved in naive T CD4+ cells differentiation process. Compared with αβT cell,γδT cells are able to directly identify various forms of stress antigen, phosphorylated antigen and heat shock protein homologue molecules through TCRγδ molecule without the help of APCs. On the other hand, the activated DETCs could secrete large amounts of IL-2, TNF-a, IFN-γ and other immune-activative factors. Therefore, it was suggested DETC in the skin should function as LCs to start immune rejection after skin transplantation. In this study we preliminarily explore the role of DETC in immune rejection of skin allograft in mice and its possible mechanism by in vivo and in vitro models.Methods1. A skin graft model was established from male to female C57 BL/6 mice with homologous but small differences of MHC molecules. The survival times of skin grafts were compared between the wild type mice(WT) and the γδ gene knockout mice(GK).2. The features of phenotype, morphological characteristics and molecular expression of DETCs in skin were detected by immunofluorescence and flow cytometry.3. The effect of DETCs on na?ve CD4+ T cell differentiation was checked by coculture.4. The effect of IFN-γ on the survival time of the skin grafts was observed after the neutralized antibodies were injected into the recipient mice.5. The changes of IFN-γ expressions were measured after the DETCs from skin was stimulated with Con A..Results1.The survival times of skin grafts of mice in group GK was 22-35 d, obviously longer than that in group WT(12-16, χ2=14.1,P<0.01)2.DETCs accounted 7.27% in epithelial cells of skin in mice, they were all CD3+cells. DETCs were found to be scattered in the epidermis of skin with dendritic morphology.3.DETCs could induce na?ve CD4+ T cells to differentiate to Th1 cells.4.The survival times of skin grafts of mice in group IN was 10-24 d, which was obviously longer than that in control group(12-16, χ2=13.6,P<0.001), but close to that in group GK as in part one(χ2=0.06,P=0.81).5.After DETCs derived from skin were stimulated with Con A, IFN-γ positive cells were increased from 0.51% in control group to 22.70%.ConclusionDETCs were involved in immune rejection of skin allograft probably by secreting IFN-γ.