Expression of Notch1, Notch2, Jagged1, and Jagged2 in B-CLL and normal B cells. The expression of Notch1 (A), Notch2 (B,C), Jagged1 (D), and Jagged2 (E) proteins was analyzed by Western blot in whole-cell lysates (25 μg for Notch1 and Notch2 using mAbs directed to N-IC domains, 70 μg for Notch2 using an Ab directed to N-EC domain, and 60 μg for Jagged1 and Jagged2) extracted from freshly isolated B-CLL cells (n = 25) and PBMCs, PBLs, and B-CD19⁺ cells from healthy donors (n = 5). Results from 8 B-CLL patients having different characteristics and 1 representative healthy donor are shown. Whole-cell lysates isolated from KM-H2 and B-JAB cell lines were used as positive and negative controls, respectively, for receptor expression. Whole-cell lysates isolated from IM-9 and Jurkat cell lines were used as positive controls for Jagged1 and Jagged2 expression, respectively. Whole-cell lysates isolated from NIH-3T3 cell line were used as a negative control for expression of both ligands. Protein loading was assessed by reprobing the blots with an anti–β-actin mAb.