MHC CLASS-II AND INVARIANT CHAIN BIOSYNTHESIS AND TRANSPORT DURING MATURATION OF HUMAN PRECURSOR DENDRITIC CELLS

Dendritic cells (DC) are highly potent activators of the immune respon se. The precise mechanisms that give rise to the DC phenotype are not known. To investigate the mechanisms that contribute to the generation of the DC phenotype, precursor DC were freshly isolated from human bl ood and allowed to mature in vitro. These matured DC showed the phenot ypical and functional characteristics of DC. Analysis of the MHC class II and invariant chain (li) biosynthesis revealed that upon maturatio n, class II synthesis was induced whereas ii synthesis was significant ly up-regulated. In mature DC, despite the presence of large amounts o f ii, export of MHC class II molecules from the endoplasmic reticulum was incomplete, up to 4 h after biosynthesis. Thus, MHC class II-ii sy nthesis and transport in DC is highly regulated during maturation of D C. Analysis of the regulatory mechanisms may contribute to a better un derstanding of antigen-presenting capacities during the differentiatio n of DC.