Efficacy of Immunomodulatory Therapy with All-Trans Retinoid Acid for Adults with Chronic Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an immune-mediated disorder characterized by antibody- and cell-mediated platelet destruction and impaired platelet production. In addition of antibody-mediated platelet clearance, T-cell is also involved in platelet destruction or marrow suppression. During immune responses CD4+ T cells can differentiate into a range of cell types, including T helper type 1 (Th1), Th2, Th17 and regulatory T cells (Treg). The goal of the present study is to investigate the therapeutic effects of all-trans-retinoic acid (ATRA) plus prednisone treatment on adult refractory idiopathic thrombocytopenic purpura (RITP) and to further explore the underlying mechanisms.

All 35 patients were treated with ATRA at fixed dose of 10 mg/tid plus prednisone and were started after discontinuation of other previous ITP treatment. Peripheral blood samples were collected from 35 RITP patients and 20 healthy subjects. The concentrations of the peripheral blood CD 4+ T cells (Th1, Th2, TH17, TREG) were analyzed by flow cytometry, the levels of cytokines were confirmed by enzyme-linked immunoassay (ELISA), and the expression of T-bet, GATA-3, RORγt, FOXP3 were detected by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) in 35 RITP patients before and after treatments, with 20 normal individuals as respective controls.

The overall response rate of ATRA plus prednisone treatment in RITP patients was 54.3%, 28.6%(n=10) of patients with a complete response and 25.7%(n=9) of patients with a partial response. Among the 19 responders, the mean platelet count was 34+13×10⁶/ml before ATRA therapy and 106+29×10⁶/ml after treatment. No severe adverse effects happened. The levels of regulory T cells were significantly increased in patients after ATRA plus prednisone treatment (P < 0.05); the levels of Th1, Th2, Th17 were not significantly improved (P >0.05) in effective patients after treatments in flow cytometry analysis. The concentrations of IL-10, TGF-β was increased (P<0.05), whereas IFN-γ, IL-4, IL-17 factor showed no obvious change in the effective groups after treatment (P > 0.05). The expression levels of Foxp3 enhanced dramatically after treatment in real-time RT-PCR analysis (P < 0.05). However, the concentrations of T-bet, GATA-3 and ROR-γ showed no obvious change after the therapy in real-time RT-PCR analysis(P > 0.05).

54.3% of RITP patients recovered after ATRA plus prednisone treatments. The therapeutic effects of ATRA plus prednisone may be involved in the increased levels of regulory T cells in peripheral blood through increased expression of TGF-β, IL-10, and Foxp3. In comparison, the therapeutic effects may not be attributed to the expression of TH1, TH2, TH17, IFN-γ, IL-4, IL-17, T-bet, GATA-3, RORγt.

No relevant conflicts of interest to declare.