Figure 4. CK2, CD5, and BLNK form a phosphorylation complex that facilitates the phosphorylation of STAT3 on serine residues.

(A) CLL cell lysates from two randomly selected CLL patients were immunoprecipitated with anti-STAT3 antibodies. The immune complex was separated using SDS-PAGE, and STAT3, serine pSTAT3, CK2, BLNK, and CD5 were detected in the immunoprecipitate by Western immunoblotting. HeLa and Jurkat cells were used as controls. I.P., immunoprecipitate; B, beads. (B) Similarly, CLL cell lysates were immunoprecipitated with anti-CD5 antibodies. The immune complex was separated using SDS-PAGE, and STAT3, serine pSTAT3, BLNK, CD5, and CK2 were detected in the immunoprecipitate by Western immunoblotting. HeLa, Jurkat, and HEK293 cells were used as controls.