Stimulation of the mouse immune system by dUTPase can induce immune-modulatory effects that resemble the clinical symptoms observed in ME/CFS sufferers including reduction in body mass and physical activity that correlated with increased production of inflammatory cytokines (TNFα, IL-1β, IL-6) together with enhanced Natural Killer (NK) cell activity and IFNγ synthesis. This evidence concerns the gene IL1B and myalgic encephalomeyelitis/chronic fatigue syndrome.