Elevated Expression of IL-17 and IL-23 in Patients with Immune Thrombocytopenic Purpura

Introduction: In conjunction with IL-6 and TGF-β, IL-23 stimulates naïve CD4+ T cells to differentiate into Th17 cells. Th17 cells produce IL-17, a pro-inflammatory cytokine that play an important role in the pathogenesis of several autoimmune disorders. However, to date, the role of Th17 cells in immune thrombocytopenic purpura (ITP), a type of autoimmune diseases, has not been clearly established yet.

Methods: Peripheral bloods were obtained from 10 patients with ITP at onset, in remission and from 15 healthy control subjects. The frequencies of IL-17 producing T cells in peripheral blood were analyzed by flow cytometry. Peripheral blood Mononuclear cells (PBMCs) were isolated using Ficoll density-gradient centrifugation and the CD4+ cells were separated by immuno-magnetic microbeads selection. Plasma concentrations of Th17 cell-associated cytokines such as IL-12, IL-17, IL-23, IFN-γ, IL-6 and TGF-β were measured using ELISA. The mRNA expression levels of IL-17, IL-12p40, IFN-γ, IL-23p19 in CD4+ cells were determined by Real-Time PCR.

Results: The frequencies of IL-17-producing T cells were significantly increased in ITP patients at onset, compared to ITP patients in remission (10.7±5.5 % vs 4.1±3.5 %, p < 0.05) and healthy controls (10.7±5.5 % vs 2.1±1.6 %, p < 0.05), however there was no statistical difference between ITP patients in remission and healthy controls. Comparing to healthy subjects, the plasma concentrations of IL-12 (33.3±15.25 pg/ ml vs 12.8±7.24 pg/ml, p<0.05), IL-17 (37.3±12.1 pg/ml vs 5.1±3.6 pg/ml, p < 0.05), IL-23 (30.01±9.33 pg/ml vs 10.42±13.19 pg/ml, p < 0.05) in patients with ITP at onset were found significantly elevated whereas no statistical difference was observed for the levels of IL-12, IL-17 and IL-23 between ITP patients in remission and healthy controls. Furthermore, the expression levels of IL-23p19 mRNA were significantly increased in ITP patients at onset, compared to healthy controls. Changes in IL-23p19 mRNA expression and IL-17 were strongly correlated (R = 0.66, p < 0.05).

Conclusion: Our results support the hypothesis that Th17 cells are involved in the development of ITP and Th17 cells could potentially constitute a novel therapeutic target.