| Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is an important way to treat leukemia, lymphoma, multiple myeloma, and other malignant diseases of the blood system, as well as some benign blood diseases, immune system diseases and solid tumors. After Allo-HSCT, the donor's immune system replaced the host's immune system, the host antigen (HLA antigen mainly) induced graft-versus-host disease (GVHD), resulting in graft failure. To avoid GVHD, HLA must matching completely, which limits the clinical application of hematopoietic stem cell transplantation . We induced immune tolance to the hose in donor embryonic stage, with mononuclear cells as antigen, which express lots of HLA antigens. Then, transplanted hematopoietic stem cell, in order to prevent GVHD, and ultimately take hematopoietic stem cell transplantation to be feasible.In this experiment, normal rats as subjects, divided into four groups. Including: induced tolerance group, tolerance blank group, irradiation transplantation group and simply irradiated group. Induced tolerance Group was the experimental group, and the others were the control groups. Simply irradiated group included 15 Wistar rats, and the remaining three groups included 15 male SD rats and 15 female Wistar rats. In embryonic stage of Experimental group SD rats, induced immune tolerance to Wistar rats by inject peripheral blood mononuclear of host to donor's yolk sac. When donor was mature, extracted bone marrow by Bone marrow needle, and separated bone marrow mononuclear cells by Ficoll separated liquid. The cell counts was about 1×107, 0.2 mlPBS to diluted, and then transplanted bone marrow cells in bone marrow cavity. 24 hours before transplantation, given receptor 60Co 8.0Gy lethally irradiation. After transplantation, testing the following indicators: 1, Receptor's general condition (including apparent and survival time). 2, The reconstruction of hematopoietic system: After irradiation, tested receptor's peripheral blood leukocyte count every four days; Used PCR technique to detect White blood cells , which come from Donor; then did bone marrow smear. 3, GVHD histopathological examination and reconstruction of the immune system: histopathological examination included liver, spleen, intestine and skin. The donor and host rats taken 3 pieces of back skin to graft, each about 1 cm×1cm, including:autologous skin grafting, the normal rat allograft transplantation and for the skin and the exchange of receptor skin transplantation.The results: 1, The receptor's general condition:After recepted lethally irradiation, the general state was poor. Control rats'autopsy shows bleeding and signs of infection.Which was not found in experimental rats. After irradiation, the100 days survival of Experimental rats was 86.7 percent, while the control group were 6.7%, 0% and 0%. Experimental group receptor's survival rate was significantly higher than that of the control group. 2, GVHD histopathological examination and reconstruction of the immune system: the experimental group found no immunological rejection, that is, without GVHD phenomenon. The liver, spleen, intestine and skin of the Experimental control group (except simple irradiation group) were infiltrated by inflammatory cells obviously, shows that there exists an obvious immunological rejection (GVHD phenomenon). Experimental skin graft shows that receptor in rats rebuild the immune system, immune function was normal, and immune tolerance was successfully inducted. 3, the hematopoietic system: (1)After received lethally irradiation, the experimental group's hematopoietic system was completely destroyed. The peripheral blood leukocyte count decreased significantly in the first eight days and reached the lowest value.Which was rebounded in the 12th days after irradiation (11 days after the transplant). Until the 20th days after irradiation (19 days after transplantation), peripheral blood WBC count has rebounded to the normal range. (2) Bone marrow smear shows: myelodysplastic good. (3) 31 days after exposure (30 days after transplantation), detected the source of donor leukocytes by PCR technique. The experimental results show that: embryonic phase induction of immune tolerance, and then conventional hematopoietic stem cell transplantation, the host's hematopoeitic system and immune system to rebuild.Conclusion: 1, Through induce fetal immune tolerance in application of hematopoietic stem cell transplantation can prevent GVHD effectively, and significantly increase the quantity and quality of the survival. (1)In this test, the host's hematopoeitic system and immune system was substituted by donor's hematopoeitic system and immune system. (2) In this test , immunosuppressive drugs should not be used, the host can survive without the occurrence of GVHD. (3) Induced by fetal immune tolerance had replace the MHC matching before transplantation in rats'vivo. 2, The experimental operation was feasibile. (1)The rat embryonic yolk sac is an inoculated alloantigen-way. (2) bone marrow cell transplantation Intro bone marrow cavity is an effective method of hematopoietic stem cell transplantation.Allogeneic hematopoietic stem transplantation is a very important method in the treatment of leukemia, which must be the study hotspot. Through induce immunotolerance in the experimental rat embryos in vivo, and then transplanted bone marrow cells, can avoid the occurrence of GVHD successfully .
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