Low-dose chidamide increased CD4⁺CD25⁺Foxp3⁺ Treg cells in ITP patient PBMCs and enhanced immunosuppression function of CD4⁺CD25⁺ Treg cells. (A) Low-dose chidamide (10 nM) increased the percentage and number of CD4⁺CD25⁺Foxp3⁺ Treg cells in ITP patients. (B) We found no significant change in the percentages of CD4⁺CD25⁺Foxp3⁺ Treg cells in healthy volunteers after chidamide treatment. (C) The percentage of CD4⁺ T cells did not vary significantly before and after chidamide treatment. (D-E) Low-dose chidamide (10 nM) stimulated Treg cells to inhibit effector T cells. Coculture of chidamide and Treg cells resulted in a significantly lower proportion of effector T cells during the proliferation stage than those without chidamide treatment. *P < .05, **P < .01.