Fig. 4. Truncation of DRß cytoplasmic tail beyond Arg232 hinders ER egress. (A) HEK 293T cells were transiently co-transfected with the indicated chimeric molecules and with pREP4 Iip35 LI/ML and tested after 48 hours. Cells were analysed by flow cytometry using BU45 either before (surface Ii) or after (total Ii) permeabilization with saponin. The ratios of surface to total Ii are shown. The total ISCR3 mean fluorescence value (MFV) for all the chimeric class II molecules was between 223 and 248. The MFV for the secondary antibody alone was 5 (data not shown). (B) Hela cells stably expressing the indicated class II molcules were supertransfected with Iip35 LI/ML cDNA and stained for Ii using BU45.