To Evaluate the Inhibition Leukemia Cell Effect of Haploidentical Spleen in Nonmyeloablative Allogeneic Hematopoietic Stem Cell Transplantation

[Objective] To evaluate the inhibition leukemia cell effect of haploidentical spleen in nonmyeloablative allogeneic hematopoietic stem cell transplantation.

[Method] Take C57/BL/6 inbred mice (B6 mice) of 8-12 weeks as donor rats. Extract their bone marrow and spleen cells. P815 cells were as mast cell tumor cells (leukemia cells) of DBA/2 mice. The first generation 6D2F1 rats (F1 rats) were as recipients who were hybridized by C57/BL/6 mice and DBA/2 mice. F1 rats were made with the nonmyeloablative conditioning regimen CTX 300mg/m2 /d intraperitoneal injection on the hematopoietic stem cell transplantation -5d, -4d, -3d. In day 0, Group A-D were infused spleen + bone marrow cells +P815 cells; bone marrow cells + P815 cells; P815 cells and RPMI1640 culture medium respectively to compare the status of the mice blood, aGVHD and the pathological tumor infiltration of skin, liver and colon.

[Results] 1. aGVHD score: the aGVHD score of group A was 2-4 who were alive on the 14th day after transplantation. The death occured on the fifteenth day. The clinical score was 6 on the twenty-sixth day for the 2 alive mice, and the rest of the mice were scored at 0-3. In group B, the mice began to die on the sixth day, and only 1 survived at the end of the thirtieth day. Group C died all in eighteenth days. 2. Pathological observation: the liver inflammatory cell infiltration in Group A, portal area of liver cell atrophy and necrosis of hepatic portal area and central veins focal infiltration of tumor cells or a small amount of infiltration could be observed. In Group B, the number of hepatocytes in the liver of the mice was decreased, and the infiltration of the tumor in the liver sinus was diffuse.

[Conclusion] In nonmyeloablative allogeneic hematopoietic stem cell transplantation, the MHC haploidentical spleen may inhibit leukemia cell effect.

[Discussion] Group A, compared with Group B and C, showed the aGVHD effect, as well as GVL effect. The spleen of haploidentical nonmyeloablative hematopoietic stem cell transplantation may make chimerism of immune cells of B6 mice and hematopoietic immune cells of F1 mice. The activated lymphocyte of the spleen of B6 mice and F1 mice could identify, monitor, inhibit and kill P815 cells. In nonmyeloablative allogeneic hematopoietic stem cell transplantation, the MHC haploidentical spleen may inhibit leukemia cell effect.