Figure 4.

Localization of lysosomal markers CD63 and LAMP1 indicate that the electron-dense MDLs are lysosomal. In IMDCs (A), LAMP1 (15-nm gold) is mostly present on the limiting membrane of the multilamellar lysosomes, whereas CD63 (10-nm gold) can be detected on both internal and limiting membranes. On maturation with LPS (B), both LAMP1 (15 nm) and CD63 (10 nm, arrowheads) can be detected on the membrane of electron-dense structures with altered ultrastructure lacking the internal membrane structures and denoted MDLs and indicated by asterisks. Scale, 200 nm. G, Golgi complex; e, endosomes; m, mitochondria; p, plasma membrane.