Analysis of ZAP-70 and Syk activation in transiently transfected primary CLL B cells. Primary CLL B cells lacking endogenous ZAP-70 were transiently transfected by nucleofection (ncl) with ZAP-70 or with empty vector as control. Sixteen hours after nucleofection the cells where stimulated for the indicated times with anti-IgM. Immunoblotting was performed with phospho-ZAP-70^Tyr319/Syk^Tyr352 antibody, followed by anti–ZAP-70 and anti-Syk.