Background: Antithymocytic globulin (ATG) and post-transplant cyclophosphamide (PTCy) are the most commonly 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.

Method: We collected peripheral blood sample 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, relapse rate between 3 group: ATG, PTCy and ATG plus PTCy group.

Results: We enrolled 68 patients (28 in ATG, 17 in PTCy and 23 in ATG plus PTCy) in total. In ATG group, all patients received human leukocyte antigen (HLA) matched-donor HSCT, whereas in the PTCy group, 12 (70.6%) patients received haplo-identical HSCT, and in ATG plus PTCy group, all patients received haplo-identical HSCT (p<0.001). The conventional CD25+FOXP3+Treg count of CD4+T cell was 6.14% in ATG, 12.96% in PTCy and 14.48% in ATG plus PTCy group, respectively (ATG vs PTCy, p=0.0020/ ATG vs ATG plus PTCy, p<0.0001). The naïve Treg count of CD4+T cell was 5.22% in ATG, 5.64% in PTCy, and 6.17% in ATG plus PTCy group (p=0.4643). The effector Treg count of CD4+T cell was 4.13% in ATG, 5.57% in PTCy, and 5.85% in ATG plus PTCy group (p=0.2816). The non-suppressive Treg count of CD4+T cell was 23.75% in ATG, 19.82% in PTCy, and 21.37% in ATG plus PTCy group (p=0.3767). The cumulative incidence of Grade 2 to 4 acute GVHD was 18.3% in ATG, 38.1% in PTCy, and 4.8% in ATG plus PTCy group (p=0.032). And extensive chronic GVHD was 19.4% in ATG, 28% in PTCy, and 21% in ATG plus PTCy group (p=0.615). OS and relapse rate were not statistically different between three group.

Conclusion: There were more conventional CD25+FOXP3+Tregs in PTCy-containing group than in ATG alone group, which was a result of the fact that there were more naïve and effector Treg in PTCy-containing group. ATG plus PTCy showed better outcomes for acute GVHD. Therefore, ATG plus PTCy is more recommended for the prevention of acute GVHD in haplo-identical HSCT.

Disclosures

No relevant conflicts of interest to declare.

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2024
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