Biallelic loss-of-expression or loss-of-function (LOF) STAT1-deficiency in humans is detrimental, with most patients succumbing to lethal infections with mycobacteria or herpes simplex virus 1 (HSV-1) encephalitis before the age of two years (66), which is accompanied by a profound effect on NK cell cytotoxicity (94). Here, STAT1 is linked to infection.