Table 1.

Distribution of HRP and class II molecules in Laz and B4.14 cells incubated for 2 h at 19°C in the presence of HRP-Tf

Molecule	Laz-B29		B4.14
	Multivesicular and multilamellar compartments	Early endocytic compartments	Multivesicular compartments	Early endocytic compartments
MHC class II (%)	83	17	84.5	15.5
HRP (%)	8	92	22.2	77.8

Ultrathin cryosections were immunogold labeled with the anti-αβ-DR Ab (PAG-10; Laz cells) or with the anti-class II mAb M5.114 (PAG-10; B4.14 cells) and with the anti-HRP Ab (PAG-15). Early or late endosomal structures containing either one of the labeled molecules or both were counted, and the distribution of the two markers in each type of compartment was determined. In each case, 50 cell profiles were analyzed.