Figure 6.

Early endosome inactivation delays MHC class II molecule maturation and transport to the cell surface. Cells were processed as for Figure 5. MHC class II molecules were immunoprecipitated with the Y3P mAb in B4.14 and T2bb cells and with the L243 mAb in Laz cells. (A) B4.14 cells; the samples were not boiled before SDS-PAGE analysis to detect the compact mature forms of class II molecules. (B) Laz cells; because the L243 mAb stronglyassociates with the class II molecules, samples were boiled before analysis to dissociate class II-L243 aggregates. No class II molecules are detected before 1 h of chase in control cells and 2 h in cross-linked cells, because L243 mAb does not detect immature αβ-Ii complexes. (C) T2bb cells; samples were boiled before analysis.