A NOVEL LYSOSOME-ASSOCIATED MEMBRANE GLYCOPROTEIN, DC-LAMP, INDUCED UPON DC MATURATION, IS TRANSIENTLY EXPRESSED IN MHC CLASS-II COMPARTMENT

We have identified a novel lysosome-associated membrane glycoprotein l ocalized on chromosome 3q26.3-q27, DC-LAMP, which is homologous to CD6 8. DC-LAMP mRNA is present only in lymphoid organs and DC. A specific MAb detects the protein exclusively in interdigitating dendritic cells . Expression of DC-LAMP increases progressively during in vitro DC dif ferentiation, but sharply upon activation with LPS, TNF alpha, or CD40 L. Confocal microscopy confirmed the lysosomal distribution of the pro tein. Furthermore, DC-LAMP was found in the MHC class II compartment i mmediately before the translocation of MHC class II molecules to the c ell surface, after which it concentrates into perinuclear lysosomes. T his suggests that DC-LAMP might change the lysosome function after the transfer of peptide-MHC class II molecules to the surface of DC.