Figure 2.

Characterization of MIICs in 6H5.DM cells. Ultrathin cryosections of 6H5.DM cells were immunolabeled with antibodies specific for LAMP-1 (A), I-chain COOH terminus, (B), CD-MPR (C), and peptide-loaded I-A^b (C and D, YAe). LAMP-1 (10-nm gold particles) is present on a multilaminar type 6 compartment (A), which also contains DR labeling (15-nm gold particles). In addition, both LAMP-1 and DR are found on a type 3 compartment, although to a smaller extent than on the type 6 compartment. I-chain COOH terminus labeling is restricted to type 2, 3, and 4 compartments (B), whereas DR is present in the multivesicular type 4 and more abundantly on the mixed type 5 compartment. Two typical type 6 compartments are shown in C; one of them shows labeling with YAe (10-nm gold particles). CD-MPR is absent from the type 6 compartments; labeling of CD-MPR (15 nm) is restricted to small, dense vesicles. YAe labels both on a type 3 and type 6 compartment (D). Bars, 100 nm.