Fig. 5. Depletion of -adaptin does not significantly affect the steady-state distribution or initial endocytosis rate of MHCI. (A) Control, clathrin or -adaptin-depleted cells were prepared, and relative steady-state levels of TfnR and MHCI at the cell surface were determined by flow cytometry (see Materials and Methods for details). (B,C) MHCI at the cell surface was labeled by incubation of cells with anti-MHCI antibody on ice. Cells were returned to 37°C for 5-10 minutes (B) or 20-120 minutes (C) to allow resumption of trafficking. MHCI that had remained at the cell surface was detected using FITC-conjugated secondary antibody, and levels were then quantified by flow cytometry. Data represent results from at least four independent experiments, each performed in duplicate; ^**P values (ranging from P=0.001 to P=0.01) indicating statistically significant differences.