Peripheral blood T cell subset characteristics of multiple sclerosis in remission phase correlate with annualized relapse rates

Objective A large number of disease-modifying drugs are available for multiple sclerosis (MS); however, there is no established biomarker to predict long-term disease severity and future relapses in MS. We aimed to clarify the alterations in peripheral blood T cell subsets that are associated with MS relapse and disease severity, according to cytokine production profiles in the remission phase. Methods Blood samples collected from 29 relapsing–remitting MS patients in the remission phase and 21 healthy controls (HC) were analyzed for various cytokine-producing T cell subsets by flow cytometry. Results MS patients in the remission phase had significantly higher percentages of interleukin (IL)-17+CD4+ T cells, IL-4+CD4+ T cells, IL-9+CD4+ T cells, interferon-γ+CD8+ T cells and IL-4+CD8+ T cells than HC (P = 0.047, P = 0.007, P = 0.026, P = 0.015 and P = 0.007, respectively). In MS, the percentages of IL-9+CD4+ T cells, IL-9+CD8+ T cells and IFN-γ+IL-17+CD8+ T cells showed a significant positive correlation with annualized relapse rates (ARR) (P = 0.011, r = 0.47, P = 0.007, r = 0.49 and P = 0.044, r = 0.38, respectively). Conclusions In the remission phase of MS, both anti-inflammatory cytokine-producing T cells and pro-inflammatory cytokine-producing T cells are increased; however, only the percentages of pro-inflammatory cytokine-producing T cells, such as IL-9-producing CD4+ T cells, IL-9-producing CD8+ T cells and IFN-γ- and IL-17-producing CD8+ T cells, correlate with ARR. These pro-inflammatory cytokine-producing T cells in the remission phase might be candidate biomarkers for future relapses in MS patients.