K430R-Btk corrects pre-B-cell maturation in Btk/SLP-65 double-mutant mice. Flow cytometric analysis of gated surface IgM-negative B220⁺ pro-/pre-B cells of Btk⁺, Btk^-, and K430R-Btk mice on either an SLP-65⁺ or the SLP-65^- background. B220⁺IgM^- cells were gated and analyzed for the expression of (A) cytoplasmic Igμ H chain (cμ)/SLC, (B) cμ/MHC, class II, and (C) forward scatter (FSC)/CD25. Data are displayed as dot plots and the percentage of cells within the indicated gates are given. Data shown are representative of 5 to 14 mice analyzed within each group.