Phosphorylation of Syk or ZAP-70 in CLL B cells after BCR ligation.
Lysates were prepared before and 10 minutes after BCR ligation with anti-μ F(ab′)2 and then used for immune precipitation with antibodies specific for Syk (A) or ZAP-70 (B). Each pair of lanes represents the lysates prepared from cells before (−) or after (+) BCR ligation, as indicated at the top of each sample lane. The numbers of the CLL samples are provided above each pair of lanes. CLL13 (13) and CLL14 (14) did not express ZAP-70, whereas CLL cases 1 through 4 were ZAP-70+. The top row in panels A and B provides the proteins of approximately 70 to 72 kDa that were detected by antiphosphotyrosine antibody 4G10, as marked by the left-hand arrow labeled “anti–P-Tyr.” The bottom rows in panels A and B provide the same bands identified on the stripped blots that reacted with anti-Syk (Syk) or anti–ZAP-70 (ZAP-70) antibodies, respectively, as indicated by the arrows on the left-hand side of the Figure.
