IL17A and primary progressive multiple sclerosis: As shown in Figures 3E–H, MAIT cells isolated ex vivo from RRMS patients both in remission and during exacerbations responded robustly to IL-18-driven stimulation with significantly higher expression of CD69, VLA-4, and production of IL-17, compared to PPMS patients and HCs (p < 0.01 to p < 0.0001).