MYHIIA and CLL subset 6 mAb reactivity is exposed on a subset of early and late apoptotic cells. Flow cytometric analyses of spontaneous apoptotic Jurkat cells are displayed as contour plots of fluorescence intensity shown on 4-log scales with BiExponential transformation. (A) Cells were stained with rabbit anti–human MYHIIA antibody (100 μg/mL), FITC-conjugated anti–rabbit IgG (3 μg/mL), 7AAD, and AV-PE. Representatives of 9 experiments are shown. Early apoptotic cells (7AAD⁻, AV-PE⁺, 26.3%; top left panel) were gated and contain a subset of MYHIIA⁺ cells (22.9%; bottom right panel). Late apoptotic cells (7AAD⁺, AV-PE⁺, 14.5%; top left panel) were gated and contain a subset of MYHIIA⁺ cells (9.4%; top right panel). Gated live cells (7AAD⁻, AV-PE⁻, 58.5%; top left panel) contained no MYHIIA⁺ cells (0.4%; bottom left panel). (B) Same experiment as in panel A showing MYHIIA⁺ cells (7.3%) are all AV-PE⁺ (top panel). Gated MYHIIA⁺ cells are either early (78.9%) or late (19.9%) apoptotic cells (bottom panel). (C) Cells were stained with human CLL 068 mAb (100 μg/mL), FITC-conjugated anti–human IgG (2 μg/mL), 7AAD, and AV-PE. Representatives of 23 experiments are shown. Early apoptotic cells (23.7%; top left panel) were gated and contain a subset of CLL 068⁺ cells (27.3%; bottom right panel). Late apoptotic cells (23.0%; top left panel) were gated and contain a subset of CLL 068⁺ cells (8.3%; top right panel). Gated live cells (52.4%; top left panel) contained no CLL 068⁺ cells (0.1%; bottom left panel). (D) Same experiment as in panel C showing CLL 068⁺ cells (8.7%) are all AV-PE⁺ (top panel). Gated CLL 068⁺ cells are either early (73.6%) or late (24.8%) apoptotic cells (bottom panel). (E) Cells were stained with CLL 068 mAb (50 μg/mL) plus FITC-conjugated anti–human IgG (0.2 μg/mL; x-axis) and PE-conjugated anti–rabbit IgG alone (2.4 μg/mL), AV-PE, or anti-MYHIIA antibody (200 μg/mL) plus PE-conjugated anti–rabbit IgG (y-axis; left to right, respectively). Representatives of 19 experiments are shown. In this experiment, CLL mAb 068 reacts with 36.6% cells with less than 1% background PE staining (left panel). CLL 068 only stains AV-PE⁺ cells (44.1%), with a subset of AV-PE⁺ cells negative for CLL 068 staining (19.8%; middle panel). All CLL 068⁺ cells are MYHIIA⁺ (42.8%; right panel). Cells were not stained by secondary antibodies alone (not shown).