IFNG and viral infectious disease: Experimental data for cytokine output have been well summarised by Varzaneh et al,7 where sluggish production of interleukin (IL) 2 along with deficiencies in other cytokines such as IL-4, IL-5 and IL-10 were reported by a number of studies.7–9 On the contrary, high levels of inflammatory cytokines such as IL-6, interferon (IFN)-γ and tumour necrosis factor (TNF)-α were observed.7 During the acute phase of a viral infection in immunocompetent individuals, elevations in the classical trio of IL-2, IFNγ and TNFα are typically observed.