In MS, CSF IL-17A levels are associated with disruption of the blood–brain barrier and expansion of neutrophils in CSF and directly correlated with CSF glutamate levels; IL-17A levels fall with disease duration, suggesting that glutamate toxicity may be more important in MS onset than in later stages.22 IL-17A levels tended to be lower in C-ME/CFS subjects with longer duration of illness; however, levels did not differ for atypical subjects based on disease duration. Here, IL17A is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.