Effects of self-ligand on maturation. Fresh splenocytes were stained with anti-CD3ϵ, anti-NK1.1, anti-CD27, and anti-CD11b. Propidium iodide was added to exclude dead cells. NK cells are gated as NK1.1⁺CD3⁻ and divided into subpopulations according to the expression levels of CD27 and CD11b as in Figure 3C. Surface phenotype of wild-type and BCAP^−/− NK cells from C57BL/6, H2^d congenic, and K^bD^b−/− backgrounds are shown. All of the data are representative of at least 3 mice. Numbers on plots are the percentages of total NK cells in each quadrant.