Naive wild-type (WT), Fcgr3−/− (FcγRIII−/−) or SCID (severe combined immune deficiency) mice were treated with a single dose of anti-CD27, and the expression of the activation marker, KLRG1, was monitored on peripheral blood NK cells (Figures S2A and S2B). Here, KLRG1 is linked to Immunodeficiency.