A longitudinal study examining cytokine production in ME/CFS patients tested at 0, 6, and 12 months for NK cell cytotoxicity and cytokine secretion showed inconsistent, and sometimes opposing, levels of TNFα, IFNγ, IL-10, IL-17A, and IL-2 across the three timepoints in the same individual [155]. This evidence concerns the gene IFNG and myalgic encephalomeyelitis/chronic fatigue syndrome.