Dendritic cell subsets: their roles in rheumatoid arthritis.

Dendritic cells (DC) are now known to influence many different classes of lymphocytes (T, B, NK cells) and many types of T cell responses (Th1/Th2/Th17, regulatory T cells, peripheral T cell deletion). In rheumatoid arthritis (RA) DC have been described and their roles in RA pathogenesis have been implicated. This review summarizes the data obtained so far concerning the functional characterization of several DC subsets in human RA. Moreover, the effect of TNF-alpha blockade on DC phenotype and function is also discussed. As most of the studies on DC in experimental arthritis have been conducted using (immunomodulated/tolerogenic) DC as tools to ameliorate experimental arthritis, we give some examples of how these cells may induce tolerance in vivo. Although a lot of work has been performed so far, the specific and functional roles of DC subsets in human RA and in CIA remain to be established. Achieving a detailed understanding of specific DC functions in RA holds potential for modulating DC for immunotherapy by down-regulating the autoimmune response.