KIR2DL1 and systemic lupus erythematosus: IL-15 enhanced NKAT-2 expression on NK cells from SLE patients (25.8±1.8% vs. 22.0±1.5%, p = 0.001) but had no effect on NKAT-2 expression on control NK cells (33.5±2.7% vs. 34.1±2.5%, p = 0.155) (Fig 9A and 9B).