Analysis of ZAP-70 expression in B-CLL patient cells. ZAP-70 expression has been evaluated by Western blot on CD19⁺ purified B-CLL cells. Representative examples of patients characterized by absent/low (nos. 8, 13, 12, 7) and intermediate/high (nos. 2, 14, 15, 17, 18, 6) ZAP-70 levels are shown.