CD19⁺/CD5⁺ cells of the CLL precursor state MBL express LEF-1. (A) Three representative flow cytometric analyses of peripheral blood mononuclear cells from MBL patients stained with anti-CD19, CD5, and LEF-1 antibodies. Isotype control histogram is shaded gray; LEF-1 histogram is black. Data are representative of results obtained with 8 MBL patients. (B) The change in mean fluorescence intensity (ΔMFI) between isotype and anti–LEF-1 staining in 8 MBL and 13 CLL samples. *P = .002. Horizontal lines indicate the mean of the group.