Altered peripheral helper T cells in peripheral blood and muscle tissue of the patients with dermatomyositis.

Peripheral helper T (Tph) cells, phenotypically PD-1hiCXCR5-CD4+, are a recently identified Th cell subset that relates to several autoimmune diseases. Contrary to PD-1hiCXCR5+CD4+ follicular helper T (Tfh) cells, Tph cells are not located in lymphoid organs but accumulate in inflamed tissues. This study investigated Tph cells to determine their involvement in dermatomyositis (DM). The frequency of circulating Tph and Tfh cells was evaluated by flow cytometry at baseline and after glucocorticoid treatment. The expression of Tph and B cells was determined in muscle tissue by immunohistochemistry (IHC). Further, the correlations between circulating Tph cells and clinical characteristics were investigated. Flow cytometry revealed that circulating Tph and Tfh cells were decreased in peripheral blood of DM patients compared with healthy controls (HCs). However, the muscular expression of Tph and B cells was upregulated in patients with DM compared to that in the controls by IHC. Interestingly, the increased B cells accumulated around Tph cells in infiltrated lesions. The frequency of circulating Tph cells was positively correlated with Tfh cells, CD3+ T cells, CD4+ T cells, and CD8+ T cells, whereas negatively correlated with erythrocyte sedimentation rate (ESR), interleukin (IL)-6, and IL-10 levels. Furthermore, the abnormal circulating Tph cells in peripheral blood were recovered after glucocorticoid treatment. These results indicate that Tph cells might be involved in the immunopathogenesis of DM and therefore might provide novel insight for the development of DM therapies.