Comparison of Regulatory T Cell Subpopulation Between Antithymocytic Globulin and Post-Transplant Cyclophosphamide for Prevention of the Graft-Versus Host Disease in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation
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Antithymocytic globulin (ATG) and post-transplant cyclophosphamide (PTCy) are frequently used regimens for graft-versus-host disease (GVHD) prophylaxis. However, there is lack of data about the difference of regulatory T cell (Treg) subpopulation between these two regimens. We collected peripheral blood samples at day+21 after allogeneic hematopoietic stem cell transplantation (Allo-HSCT). We analyzed Treg subpopulation by flow-cytometer and classified Treg into 3 subgroups: naïve, effector and non-suppressive Treg. And we compared overall survival (OS), the cumulative incidence of acute and chronic GVHD, and the relapse rate between ATG and PTCy group. We enrolled 45 patients (28 in ATG, 17 in PTCy) in total. In the ATG group, 16 and 12 patients underwent human leukocyte antigen (HLA) matched-sibling donor and unrelated donor HSCT, respectively. In the PTCy group, 12 patients underwent haplo-identical HSCT, and 5 patients underwent HLA-matched unrelated donor HSCT. The cumulative incidence of Grade 2 to 4 acute GVHD was 18.3% in ATG and 38.1% in PTCy (p=0.13) and severe degree chronic GVHD was 19.4% in ATG and 41.7% in PTCy (p=0.343). And OS and relapse rate were not statistically different between the two groups. The conventional CD25+FOXP3+Treg count of CD4+T cell was higher in PTCy group than in ATG group (p= 0.0020). The effector Treg subset was significantly higher in PTCy group than in ATG group (p= 0.0412). And effector Treg cell count had inverse correlation with severity of acute GVHD (p= 0.0007). Effector Tregs may be used as a biomarker to predict the severity of acute GVHD after allo-HSCT.