An infection advantage associated with strongly inhibited NK cells may follow from a process of ‘education’ or ‘licencing’ during NK cell development: specifically if stronger inhibitory signals during NK cell development set up the capacity for greater activation of NK cells during infection, as has been proposed for certain HLA-B/KIR3DL1 combinations in HIV patients (Martin et al. 2007). This evidence concerns the gene KIR3DL1 and infection.