ZAP-70 physically associates with activated Hsp90 in CLL cells. (A) Protein lysates from different cell types including ZAP-70⁺ and ZAP-70^-CLL cells, normal T and B cells, and the breast cancer cell line MCF-7 were immunoprecipitated with the indicated antibodies, including Hsp90^*, which is an antibody that recognizes the uncomplexed form of Hsp90. The bound and unbound immunoprecipitated products were probed by immunoblot using the antibodies indicated in the WB column. (B) Immunoprecipitation was used to assess the level of expression of complexed (activated) and uncomplexed (nonactivated) Hsp90 in different CLL samples (8 ZAP-70⁺ CLL and 8 ZAP-70^-CLL). The figure shows the percentage of activated Hsp90 for each sample. This percentage was calculated after analyzing the digitalized composite ratio of immunoblot signal for Hsp90 uncomplexed and total Hsp90 using the following formula: % Hsp90^active = 1-(Hsp90^*/Hsp90^total) × 100.