Long-term use of interferon-β in multiple sclerosis increases Vδ1 − Vδ2 − Vγ9 − γδ T cells that are associated with a better outcome

We previously reported that Vδ2+Vγ9+ γδ T cells were significantly decreased in multiple sclerosis (MS) patients without disease-modifying therapies (untreated MS) and were negatively correlated with Expanded Disability Status Scale (EDSS) scores, suggesting protective roles of Vδ2+Vγ9+ γδ T cells. Interferon-β (IFN-β) is one of the first-line disease-modifying drugs for MS. However, no previous studies have reported changes in γδ T cell subsets under IFN-β treatment. Therefore, we aimed to clarify the effects of the long-term usage of IFN-β on γδ T cell subsets in MS patients. Comprehensive flow cytometric immunophenotyping was performed in 35 untreated MS and 21 MS patients on IFN-β for more than 2 years (IFN-β-treated MS) including eight super-responders fulfilling no evidence of disease activity criteria, and 44 healthy controls (HCs). The percentages of Vδ2+Vγ9+ cells in γδ T cells were significantly lower in untreated and IFN-β-treated MS patients than in HCs. By contrast, the percentages of Vδ1−Vδ2−Vγ9− cells in γδ T cells were markedly higher in IFN-β-treated MS patients than in HCs and untreated MS patients (both p < 0.001). A significant negative correlation between the percentages of Vδ2+Vγ9+ cells in γδ T cells and EDSS scores was confirmed in untreated MS but not evident in IFN-β-treated MS. Moreover, class-switched memory B cells were decreased in IFN-β-treated MS compared with HCs (p < 0.001) and untreated MS patients (p = 0.006). Interestingly, the percentages of Vδ1−Vδ2−Vγ9− cells in γδ T cells were negatively correlated with class-switched memory B cell percentages in all MS patients (r = − 0.369, p = 0.005), and the percentages of Vδ1−Vδ2−Vγ9− cells in Vδ1−Vδ2− γδ T cells were negatively correlated with EDSS scores only in IFN-β super-responders (r = − 0.976, p < 0.001). The present study suggests that long-term usage of IFN-β increases Vδ1−Vδ2−Vγ9− γδ T cells, which are associated with a better outcome, especially in IFN-β super-responders. Thus, increased Vδ1−Vδ2−Vγ9− cells together with decreased class-switched memory B cells may contribute to the suppression of disease activity in MS patients under IFN-β treatment.