Stability of D^b/peptide complexes. T2D^b cells, precultured at 26°C in the presence of Brefeldin A, were incubated with peptides in complete medium. Peptides were used at different molar concentrations selected to obtain a similar MFI value. In these conditions, the level of H2-D^bexpression at time 0 was equivalent for both B6^dom1 and H-Y. T2D^b cells were then washed five times, incubated at 37°C in serum-free medium supplemented with Brefeldin A, and the density of residual D^b molecules was measured by staining with anti-D^b Ab at various time points. (A) B6^dom1/D^b expression at 0 and 12 hours. (B) H-Y/D^b expression at 0 and 12 hours. (C) Downregulation of peptide/D^b complexes over a 12-hour time frame. One representative experiment of two is shown.