The Study Of Immunopathogenesis Of NK Cell Participate In AGVHD After Nonmyeloablative Haploidentical Bone Marrow Stem Cell Transplantation

Graft versus host disease is the major complication of Allogeneichematopoietic stem cell transplantation, which affects patients’ survival,relapse and quality of life. Acute graft-versus-host disease (aGVHD)mainly affect the function of liver, skin, intestine, et al. Thenonmyeloablative pretreatment not only with low toxicity but also canobtain good therapeutic effect, it mainly adapt to older patients.Haploidentical stem cell transplantation has clinical advantages because itmakes the source of bone marrow stem cell easy. NKp46is one of theactivating receptor of NK cells, the killing activity is closely related with itsexpression level, the activated NK cells have very strong effect on killingtumor cells. NK cells is one of the first recovery immune cell afterallogeneic hematopoietic stem cell transplantation, the mechanism of NKcell in the damage of aGVHD has no profound study until now.NK cell has no MHC restriction and need no antigen stimulation whenit would kill any traget, this makes it an important cell in hematopoieticstem cell transplantation, many researches suggested that NK cell not onlyplay GVL effect in hematopoietic stem cell transplantation but also canreduce the aGVHD. NK cell’s immunoglobulin like receptor (KIR) andHLA-Ⅰmolecules mismatch reduces the kill of the receptor’s dendriticcells cell after hematopoietic stem cell transplantation, blocking the donorT cells present host antigen to reduce graft-versus-host disease, the donorderived NK cell also take part in the outcome of transplantation complications, which play a positive role in the control of CMV infectionby producting IFN-γand direct toxic effect, there is a special subset of NKcells in the digestive tract mucosa, it can promote the regeneration of thedigestive tract mucosa after aGVHD damage, Small C showed that NK cellin the lung could play the role of anti-infection and promote theregeneration of epithelial cell to time take part in the resistance andrecovery of pulmonary infection after transplantation. In this study, micenonmyeloablative haploidentical bone marrow transplantation model wasdeveloped, it investigated the immunepathology of NK cell in aGVHDtarget organs and relationship between the expression intensity of NKp46and the occurrence of aGVHD.We chose the C57BL/6(H-2b,♂) as donor, CB6F1(Balb/c×C57BL/6, H-2b/d,♀) as recipient, then developed the nonmyeloablativehaploidentical bone marrow transplantation animal model. The mice weredivided into the single total body irradiation(TBI) group and the twofractions TBI group according to the prepreprocess. Each group wasaveragely divided into3groups: control group, low dose transplantationgroup, high dose transplantation group. The mice of single TBI groupreceived200mg.kg-1cyclophosphamide (-2,-1d) intraperitoneal injectionand60Co450cGy TBI (0d), the irradiation dose rate was133cGy/min.The two fractions TBI group received cyclophosphamide200mg.kg-1intraperitoneal injection(-1d) and60Co200cGy TBI (-2,-1d,24hinterval), the irradiation dose rate of66cGy/min. On the day oftransplantation, CB6F1accepted donor bone marrow cells3×107and6×107or1×108spleen cells by tail vein injection, mice of control group wasinjected with equal volume of saline. The symptoms and signs wereobversed, the transplantation chimerism and NKp46expression intensitywere obversed by FCM, collected the skin, liver, intestinal organ of micewho were acquitted because of occurring aGVHD, HE staining was used toobserve pathological, immunofluorescence staining was used to observe the distribution of NK cells in target organs. The mice received single TBIdidn’t occur aGVHD,80%of the two fractions TBI mice occurred aGVHD.15days after transplantation,100%of the fraction TBI mice has reachedcomplete chimerism. About25d after transplantation the mice developedaGVHD typical performance of weight loss, towering hair, stooping,reduced activity. In the two detection after the mice occurred aGVHD,themean fluorescence intensity of NKp46activating receptor of aGVHD micewas higher than free-aGVHD mice. There was a few NK cell scatteredamong hepatic cells in liver tissue of free-aGVHD mice, NK cell infiltratedaround portal in aGVHD mice liver tissue. This experiment shows that inNonmyeloablative Haploidentical Bone Marrow Stem Cell Transplantation,NK cells take part in the Pathological response of liver graft versus hostdisease, NK cells’ activity is associated with the occurrence of aGVHD, itmaybe makes NKp46density as a early diagnosis index for aGVHD.