Normal human serum IgG reacts with MEACs. Spontaneous apoptotic Jurkat cells were stained with 25 μg/mL rabbit anti–human MYHIIA antibody and 25 μg/mL CLL mAb, normal human serum IgG from Sigma (S; 25 μg/mL) or Miltenyi Biotec (M; 2 μL), or 25 μg/mL humanized anti-CD20 mAb, followed by 1 μg/mL secondary antibodies: PE-conjugated anti–rabbit IgG and FITC-conjugated anti–human IgG. Representatives of 4 experiments are shown. (A) Flow cytometric analyses are displayed as contour plots of fluorescence intensity shown on log scales with BiExponential transformation. Panels show costaining with anti-MYHIIA and serum IgG or anti-CD20. (B) After gating on MYHIIA⁺ cells, histograms of the percentage of maximum (% of Max) fluorescent intensity for indicated staining (thick blue line) is shown relative to cells stained with CLL 169 mAb (thin red line). (C) The MFIR staining of MEACs was calculated as in Figure 3C except that the MFIR was calculated by dividing the MFI for MYHIIA⁺ cells stained with CLL 169 mAb.