Increased expression of interleukin-17 is associated with macrophages in chronic immune thrombocytopenia.

Interleukin-(IL-)17-mediated cells contribute to the imbalance of cellular immunity in the pathogenesis of immune thrombocytopenia (ITP). We examined samples of bone marrow (BM) clots to determine if IL-17-mediated immunological changes involve the BM and to identify clinical predictors of treatment response. We enrolled 33 patients with chronic ITP. BM clots were obtained before treatment and stained with the following markers: CD3, CD4, CD8, CD20, CD25, CD68, CD163, and IL-17. Pathological findings and clinical information, including laboratory data, were compared between the patients and 11 control subjects and between IL-17-high and -low-expression groups. Univariate analysis revealed increased cells expressing CD68, CD163, and IL-17 in the patients with ITP than in the control subjects ( = 0.02, 0.001, and 0.001, respectively). The expression of both CD68 and CD163 showed correlation with IL-17 expression ( = 0.60 and 0.48, respectively). Responses to Eltrombopag were better in the IL-17-low-expression group than in the IL-17-high-expression group ( = 0.056). Macrophages and monocytes were associated with IL-17 expression in patients with ITP. We demonstrated that ITP is associated with IL-17-expressing monocytes/macrophages and might be more difficult to treat.