MHC class I expression is not affected by PML/RARα, a dominant-negative mutant of PML.

(A) HeLa cells were transfected with the retroviral vector pBABE alone (top row), with pBABE containing GFP-PML (middle row), or GFP-PML/RARα (bottom row), using the Lipofectamine 2000 procedure. At 3 days after transfection, cells were processed for fluorescence microscopy and flow cytometry. Cells growing on glass coverslips were immunostained with anti-PML followed by GAM-Alexa 594 antibodies (red fluorescence, middle column) and counterstained with DAPI (blue fluorescence, right column). GFP green fluorescence is shown in the left column. Cells processed for flow cytometry were immunostained with anti–MHC class I mAb (W6.32) followed by GAM-PE. (B) Bivariate dot plots are shown: x-axis, green fluorescence; y-axis, red fluorescence. Percentage of GFP-positive cells (ie, of transfected cells) is reported. The negative control for MHC class I expression, obtained using isotype-matched antibodies followed by GAM-PE, is shown in gray.