In healthy individuals, these microbial metabolites regulate mucosal immune cells, including Th17, Th22, and Treg cells, an interaction that is dysfunctional in ME/CFS resulting in elevated pro-inflammatory interactions via elevated activation of γδ⊤ cells and CD8 MAIT cells with the secretion of INFg and GzA, particularly impacting health perception and social activities. Here, CD8A is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.