Multiple CLL mAbs react with MEACs. Spontaneous apoptotic Jurkat cells were stained with rabbit anti–human MYHIIA antibody (25 μg/mL) and CLL mAb (25 μg/mL), followed by secondary antibodies: PE-conjugated anti–rabbit IgG (1 μg/mL) and FITC-conjugated anti–human IgG (1 μg/mL). (A) Flow cytometric analyses are displayed as contour plots of fluorescence intensity shown on log scales with BiExponential transformation. Top left panel shows cells stained with secondary antibodies alone. Top middle panel shows cells stained with all reagents except CLL mAb. The remaining panels show staining with different CLL mAbs as indicated. (B) After gating on MYHIIA⁺ cells, histograms of the percentage of maximum (% of Max) fluorescent intensity for indicated CLL mAb staining (blue thick line) is shown relative to cells stained with all reagents except CLL mAb (red thin line). CLL 258 histogram (not shown) was similar to that of CLL 068. (C) Chart showing the MFIR staining of MEACs with 26 CLL mAbs. The MFI for CLL mAb staining of MYHIIA⁺ cells was determined from histograms as shown in panel B. The MFIR was calculated by dividing with the MFI obtained for MYHIIA⁺ cells that were stained with all reagents except CLL mAb. The CLL mAb is indicated on the x-axis. The CLL mAb subset is indicated underneath the CLL mAb numbers (subset number or “-” if not part of a subset). The bottom row of letters indicates if the IGHV of a CLL mAb is mutated (M) or not (U).