IL17A and inflammatory bowel disease: The gut microbiota from patients with IBD could decrease retinoic acid receptor related orphan receptor γt (RORγt)+ Treg cells that produce transforming growth factor-β (TGF-β) and IL-10, and elevate Th17 (T helper 17) cells with pro-inflammatory cytokines (e.g., IL-17) (57, 58).