IL17A and myalgic encephalomeyelitis/chronic fatigue syndrome: Our results indicate that ME/CFS patients differ from control healthy subjects for several serum biomarkers, including FABP-2, IL-17A, and tryptophan metabolites, such as kynurenine, serotonin, 3-hydroxykynurenine, and the ratios kynurenic acid/quinolinic acid and 3-hydroxykynurenine/kynurenine.