The transport of RT1-E2u to the surface of transiently transfected COS-7 cells is dependent on a functional TAP transporter. For all panels, graphs are from flow cytometric analyses after staining either for H2-Db with B22-249 (upper four panels), or for RT1-E2u with MRC OX-18 (lower four panels). The fine lines are for cells labelled only with PE-conjugated secondary antibody. For both H2-Db and RT1-E2u, cell surface expression was significantly reduced when an expression-plasmid for the TAP-inhibitor protein ICP47 was co-transfected. For the analyses shown in the right-hand column, the proportion of COS-7 cells expressing the MHC molecule of interest was improved by transfecting bicistronic vectors carrying a Gtx IRES-EGFP sequence after that of the MHC class I molecules (see M&M), and gating only on the EGFP-expressing cells for analysis.