Reconstitution Of T Cells At Early Stage After Allogeneic Hematopoietic SCT And Acute Graft Versus Host Disease

Chapter1:Anti-thymocyte globulin for conditioning in mismatched unrelated donor hematopoietic cell transplantation provides superior outcomesAim:Unrelated donor hematopoietic stem cell transplantation (HSCT) is a common transplantation type. If an HLA-matched unrelated donor can not be found, an HLA-mismatched unrelated donor is also applicable. But the latter will complicate with increased risk of aGVHD which will have a negative influence on survival rate. ATG, an agent used for T cell depletion in vivo, is administered as part of the conditioning regimen to decrease aGVHD rate and increase long-term survival rate after HLA-mismatched HSCT.Methods:Patients who received unrelated donor HSCT from January2010to December2012were selected and divided into2groups (HLA-matched group and HLA-mismatched group). In HLA-matched group,4.5mg/Kg ATG were added in addition to BuCy conditioning regimen. In HLA-mismatched group,6mg/Kg ATG were added. Rates of aGVHD, cGVHD, relapse and mortality were monitored and compared.Result:58patients were included in study. The Median age was28.3years (10-50). Among them,30patients received10/10HLA-matched unrelated HSCT and24patients received HLA-mismatched unrelated HSCT. After transplantation, the engraftment time, rates of aGVHD and cGVHD were not statistically different between the2groups. The mortality rate was not statistally different too but more patients died of relapse in HLA-matched group while in HLA-mismatched group, more patients died of infection. After a median follow-up of14.4months, the total2-year overall survival (OS) rate was62.5±8.4%while in HLA-matched group, OS rate was65.1±13.7%and in HLA-matched group, OS rate was61.3±11%(P=0.97). The relapse rate were significantly decreased for those who had ever developed aGVHD compared with those who did not develop aGVHD (P=0.023). The primary disease risk stratification, cGVHD rate and primary disease status were not the risk factors affecting long-term survival rate and relapse rate after transplantation.Discussion:In most studies on unrelated donor HSCT, mismatched HLA was the major cause of decreased survival rates. Mismatched HLA can lead to increased GVHD rate and increased nonrelapse mortality rate. ATG can deplete T cells both from recipients and donors, reduce T cell mediated immune attach and finally decrease transplant-related mortality in HLA-mismatched unrelated donor HSCT. In contrast to T cell depletion in vitro, low-dose ATG can reduce aGVHD rate but did not increase relapse rate.ATG might deplete some of T cell clones but spared antitumor effector T cells. Chapter2Reconstitution of Treg, Th1and Th17cells at Early Stage after Allogeneic Hematopoietic SCT and its relativity to acute GVHDAim:aGVHD is a major early complication and cause of death after allogeneic HSCT. T cells from donors are the major effector T cells that mediate aGVHD. In chapter1, we found that low-dose ATG can deplete T cells in vivo and decreased the transplant-related mortality after unrelated donor HSCT leading to the similar long-term survival rate as HLA-matched unrelated donor HSCT. In this chapter, the relationship between the restoration of T cell subsets and aGVHD rate will be analyzed so as to clarify the role of T cell subsets on aGVHD pathyphysiology and lay the foundation of finding novel markers for aGVHD diagnosis and stratification.Methods:45patients were included in our clinical study from May2012to December2012.After transplantation, peripheral blood were drawn every1-2weeks for Treg/Thl/Thl7ratio analysis by FACS. Also IL-4, IL-6, IL-10, IL-17, TGF-β and IFN-y in the serum were analyzed by CBA.Results:A total of44patients were followed up. Among them,7developed Ⅲ■-Ⅳ°GVHD and13developed Ⅰ°-Ⅱ°aGVHD. For those who developed aGVHD, within3-5days after the recovery of hematopoiesis Treg/CD4+T cell ratio were increased obviously while Thl/CD4+cells and Th17/CD4+T cell ratios were not different. When patients had the symptom of aGVHD, Thl/CD4+T cell and Th17/CD4+T cell ratio increased. While on median day of3.1before aGVHD developed, Th17/CD4+cell ratio increased obviously and Thl/CD4+T cell ratio kept stable. On median day of3.1before aGVHD developed, the levels of IL-10and IFN-y increased but IL-4, IL-6, IL-17and TGF-P levels kept stable. According to ROC curve analysis, on day3-5after hematopoiesis recovery,8%of Treg/CD4+T cell ratio indicated high risk of aGVHD development. For Th17analysis, Th17/CD4+T cell ratio increased76%between the2consecutive drawn blood indicated high risk of aGVHD development within a short period.Discussion:T cells are the major cells that mediated aGVHD. Different T cell subsets play different roles after transplantation. In our study we found that Treg/CD4+T cell ratio in early stage indicated immunosuppression degree. The level of Treg and aGVHD rate had a negative correlation. Thl cells and Th17cells, as two subsets of effector cells, had not statistical difference in early stage after transplantation. On median day of3.1before aGVHD developed, Th17/CD4+cell ratio increased obviously and Th1/CD4+cell ratio kept stable which meant that Th17cells mediated aGVHD in early stage even before the aGVHD symptom occurred. Thus Th17/CD4+cell ratio can be regarded as an early marker of aGVHD. Some cytokine levels changed before aGVHD developed which could also assist aGVHD diagnosis.