IL17A and myeloid sarcoma: •↑Shannon diversity, and richness in MS•Altered β-diversity in MS•Progressive MS: ↑Enterobacteriaceae, Ruminococcaceae FJ366134 and Clostridaceae g24 FCEY; ↓Dorea longicatena, Anaerococcus vaginalis, and Blautia faecis•RRMS and Progressive MS: ↑Akkermansia, Clostridium bolteae;↓ Dorea formicigenerans, unclassified Blautia•Akkermansia was negatively correlated with EDSS and MRI burden of MS•Akkermansia strain BWH-H3 ameliorated EAE via reducing RORγt+ and IL-17-producing γδ T cells