Modulation Of CD8~+T Cell Response In Allogeneic-hematopoietic Stem Cell Transplantation By Histone Methylation Inhibitor DZNep

Objectives:To evaluate the effect of DZNep, a histone methylation inhibitor, on preventing donor-derived CD8+T cell mediated graft-versus-host disease (GVHD) in the induction process of hematopoietic chimerism so as to induce immune tolerance through allogeneic-hematopoietic stem cell transplantation (Allo-HSCT). And to investigate the mechanism how DZNep modulate the donor-derived CD8+T cell response in Allo-HSCT.Methods:Using the MHC-matched but miHA-mismatched Allo-HSCT mouse model in which GVHD was mediated by donor-derived CD8+T cells. The data of body weight loss, long-time survival rate, GVHD clinical score and histopathology assessment of GVHD target organ/tissue were used to evaluate the effect of DZNep on GVHD prevention. Flow cytometry was applied to analyze the phenotype of donor-derived CD8+T cell so as to investigate the regulatory mechanism of DZNep. Besides these, the status of hematopoietic chimerism in recipients, the toxicity and side-effects of DZNep in vivo were also analyzed with flow cytometry method.Results:DZNep administration can improve the body weight loss (p< 0.05), long-time survival rate (p< 0.05), GVHD clinical score (p< 0.05) and GVHD target organ/tissue histopathology of mice recipients, so DZNep prevented the GVHD. DZNep reduced the absolute number of donor-derived CD8+T cell in spleen and lymph nodes (p< 0.05) through depressing the early activation of donor-derived CD8+T cell and the proliferation of host antigen-specific donor-derived CD8+T cell (p< 0.05). The analysis of phenotype showed that DZNep significantly inhibited the expression of TNF-a and IL-2 on donor-derived CD8+T cell on D8 significantly (p< 0.05), however it enhanced the expression of IL-2 on donor-derived CD8+T cell on D14 (p< 0.05). Though DZNep did not change the expression of IFN-γ, FasL, Trail, GzmB on donor-derived CD8+T cell in spleen on D8 and D14 (p> 0.05), it reduced the expression of IFN-γon donor-derived CD8+T cell in liver on D8 and D14 (p< 0.05). Due to the obviously reduced absolute number of donor-derived CD8+T cell in spleen (p< 0.05), the absolute cell number of donor-derived IFN-γ+CD8+T cell, FasL+CD8+T cell, Trail+ CD8+T cell, GzmB+CD8+T cell and TNF-a+ CD8+T cell in spleen were also reduced significantly (p< 0.05). DZNep also inhibited the generation of donor-derived effector CD8+T cell that played an important role in GVHD (p< 0.05). Moreover, DZNep did not affect the generation of hematopoietic chimerism at the time of modulating donor-derived CD8+T cell response.Conclusion:DZNep can modulate the allogeneic CD8+T cell immune response in Allo-HSCT so as to achieve the status of hematopoietic chimerism without the occurrence of GVHD. Thus, we have found a new mechanism of histone methylation inhibitor DZNep in preventing GVHD after Allo-HSCT. This new mechanism may be used to set new research direction and strategy for the induction of hematopoietic chimerism so as to achieve the immune tolerance through Allo-HSCT.