Dendritic cells in rheumatoid arthritis: Which subset should be used as a tool to induce tolerance?

Dendritic cells (DC) comprise a complex network of heterogeneous antigen-presenting cells (APC) that are critical not only to the initiation and regulation of adaptive immunity (Th1/Th2/Th17 responses), but also to the maintenance of both central and peripheral tolerance (regulatory T cells, peripheral T-cell deletion). Previous work has clearly indicated a role for DC subsets in the pathogenesis of rheumatoid arthritis (RA). Therefore, utilizing these cells as therapeutic agents could be beneficial in the treatment of RA. However, it remains unclear which DC should be used for tolerance-inducing immunotherapy: myeloid, plasmacytoid, or both? This review summarizes the data obtained thus far concerning the functional characterization of several DC subsets in human RA and accordingly explores their potential use for immunotherapy.