Neutralizations of IL-17A and IL-21 regulate regulatory T cell/T-helper 17 imbalance via T-helper 17-associated signaling pathway in immune thrombocytopenia

Abstract

Objective: The imbalance of regulatory T cell/T-helper 17 (Treg/Th17) is critical for the pathogenesis of immune thrombocytopenia (ITP) and IL-17A and IL-21 are overexpressed in ITP. The effects and mechanisms of IL-17A and IL-21 in Treg/Th17 imbalance and ITP pathophysiology are not clarified.

Methods: Peripheral blood mononuclear cells (PBMCs) and CD3⁺ T cells from ITP patients and healthy controls were treated with cytokines or antibodies to increase or neutralize IL-17A or IL-21 levels for 72 h. Treg/Th17 differentiation, apoptosis, proliferation and Th17 differentiation-associated transcriptional factors were analyzed.

Results: Natural Treg/Th17 decreased in newly diagnosed ITP patients and recovered after remission. IL-17A or IL-21 increased Th17, decreased Tregs and downregulated Treg/Th17 in vitro. Conversely, neutralization of IL-17A or IL-21 decreased Th17, increased Tregs and up-regulated Treg/Th17. The reverse effects of IL-17A or IL-21 were mediated by Th17-associated transcriptional factors. IL-17A or IL-21 enhanced STAT-1, STAT-3, STAT-5 or RAR-related orphan receptor C (RORC), whereas anti-IL-17A or anti-IL-21 mAb downregulated STAT-1, STAT-5 or RORC transcripts in ITP PBMCs. Proliferation showed no significant difference. IL-21 inhibited apoptosis in ITP PBMCs.

Conclusion: IL-17A and IL-21 induce Th17 and inhibit Tregs re-differentiation via Th17-associated signaling pathway in ITP patients in vitro. It highlights the potential value of IL-17A or IL-21 blockade as a novel therapeutic target for ITP.

Keywords:

• immune thrombocytopenia
• regulatory T cell
• T-helper 17
• T-helper 17 cytokines

Acknowledgment

Y Hu and X Wang have equally contributed to this work.

Declaration of interest

The authors were supported by grants from National Natural Science Foundation of China (No. 81070407, No. 81170515, No. 81270578, No. 81470284, No. 81470319). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

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