The role for IL-10 in the function of FOXP3+ cells, including Tregs, is not clear and the consequences of IL-10-production by circulating FOXP3+ cells upon stimulation with S. aureus-CFS seen in our study might therefore be multiple and indicative of an immunosuppressive and/or regulatory phenotype, however this needs to be investigated further. Here, IL10 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.