Peripheral blood Th9 cells reconstitution and its relationship with acute graft-versus-host disease after matched-sibling peripheral blood hematopoietic stem cell transplantation

T helper type 9 (Th9) cells have recently been identified as a new effector T cell subset. This study is to analyze the reconstitution of Th9 cell after matched sibling peripheral blood hematopoietic stem cell transplantation (MS-PBSCT) and the relationship between Th9 cell and acute graft-versus-host disease (aGVHD). Flow cytometry and ELISA were used to analyze the percentages of Th9 cell, levels of IL-9, TGF-β, IFN-γ, and IL-4. The results showed that for patients without aGVHD, Th9 cells recovery started from day 60 after transplantation and reached normal level on day 90. Serum TGF-β, IL-4, and IFN-γ reached normal levels on day 60, 60, and 90 post transplantation respectively. The serum IL-9 recovery is slower than that of IFN-γ and IL-4. For patients suffering from aGVHD, they had declined Th9 cell numbers, lower IL-9 and TGF-β levels, but higher serum IFN-γ level when compared with those without aGVHD after transplantation. Serum IFN-γ/IL-9 ratios increased linearly with grades of aGVHD. In conclusion, Th9 cells recovery is delayed after MS-PBSCT in patients with aGVHD but early in patients without aGVHD, indicating quick immune reconstitution of Th9 cells and IL-9 after MS-PBSCT may promote the immune tolerance.