DENDRITIC CELL MATURATION AND ANTIGEN PRESENTATION IN THE ABSENCE OF INVARIANT CHAIN

In immature dendritic cells (DCs), major histocompatibility complex cl ass II molecules accumulate in peptide-loading compartments and, durin g DC maturation, are exported to the cell surface in response to infla mmatory stimuli, Moreover, it has recently been proposed that DCs have specific mechanisms of antigen uptake and delivery into major histoco mpatibility complex class II-loading compartments, B cells bearing a g enetically disrupted invariant chain gene (Ii -/-) show alterations in the transport and function of class II molecules, We herein report th at DCs derived from Ii -/- H2(k) but not Ii -/- H2(b) mice undergo nor mal maturation in response to tumor necrosis factor alpha and show a h igh degree of class II surface expression, Class II molecules are accu mulated in cathepsin D-and H2-M-positive compartments in immature Ii - /- DC and, during DC maturation, are exported to the cell membrane as compact dimers. Ii -/- DCs present putative Ii-dependent hen egg lysoz yme-derived epitopes to T cells, These data support the existence of I i-independent molecular requirements for class II transport and peptid e loading in DCs.