Morphology of class II MHC–rich endosomal vesicles.
A. Immunoelectron micrograph of a B lymphocyte that has internalized bovine serum albumin into early endosomes (labeledwith 5-nm gold particles, arrow) and contains class II MHC mole-
cules (labeled with 10-nm gold particles) in MIICs (arrowheads).
The internalized albumin will reach the MIICs ultimately.
(From Kleijmeer MJ, S Morkowski, JM Griffith, AY Rudensky, and HJ Geuze. Major histocompatibility complex class II compartments in human and mouse B lymphoblasts represent conventional endocytic comp rtments.
Reproduced from The Journal of Cell Biology 139:639–649 1997, by copyright permission of The Rockefeller University Press.)