Increased mature splenic NK cells and shift in expression of Ly49 receptors in BCAP^−/− mice. (A) Surface staining of NK cells (CD3⁻NK1.1⁺) is shown, with BCAP^−/− cells represented by the thicker line. Histograms with equal numbers of cells are compared, and the percentage of cells in each gate is indicated. (B) Expression of inhibitory Ly49 receptors as a function of CD11b expression. NK cells were stained for CD11b and either Ly49A and Ly49F or Ly49I. (C) Relationship between CD11b expression and CD27 expression in BCAP^−/− and wild-type NK cells. Quadrants labeled R1, R2, and R3,³¹  define immature NK cells (R1) and 2 functionally distinct mature subsets (R2 and R3), and the percentage of cells in each quadrant is listed. (D) Expression of self-recognizing and non–self-recognizing inhibitory Ly49 receptors on NK cells from wild-type (■) or BCAP^−/− mice (□) as a function of maturity. Cells within R1, R2, and R3, as in panel C, were further stained for either Ly49I, or Ly49A and Ly49F. Error bars show the SD from 5 mice (*difference with P < .01). All data shown in this figure are representative of at least 3 experiments.