IFNG and myalgic encephalomeyelitis/chronic fatigue syndrome: A previous large study based on samples from the UK biobank found no difference in functional markers [intracellular IFN-γ or cell surface expression of CD25 or CD107a] using cryopreserved PBMCs from ME/CFS patients and healthy controls stimulated with K562 cells or cross-linking antibody to CD16 [7].