IFNG and myalgic encephalomeyelitis/chronic fatigue syndrome: Several immunologic abnormalities during acute illness appear to be risk factors for subsequent ME/CFS: higher levels of interleukin-12 (a proinflammatory cytokine) and lower levels of interleukin-5 and interleukin-13 (anti-inflammatory cytokines)12,46; a particular pattern of cytokines9; cytokine networks that are disconnected from interferon-gamma signaling, possibly indicating a vulnerability to viral infections49; and deficient EBV-specific B- and T-cell memory50.