Epidermal Langerhans cells: from neurons to nature's adjuvants

Once obscure cells of interest to only a few dermatologists, LCs have become perhaps the best studied of all the nonlymphoid DCs. Seminal studies carried out by Steinman and co-workers over a number of years have demonstrated that interdigitating DCs are required for the priming of naive T cells in vivo and that LCs (and presumably other DCs) are precursors of interdigitating DCs. These observations have sparked an explosion of research activity directed toward increasing our understanding of the biology of LCs and other DCs and exploiting their unique functional properties for the prevention and treatment of disease. This chapter represents an attempt to provide an introduction to this exciting field. We have briefly reviewed the history of LC research, summarized a number of important concepts in LC/DC biology, and highlighted the involvement of LCs in several diseases or pathophysiologic conditions. We have emphasized recent studies of DC-based immunotherapy and the roles that LCs/DCs play in genetic vaccination because we believe that LC/DC research will have an impact on patient care in these areas. The past few years have been a period of rapid progress in basic research in LC/DC biology, and many important discoveries have been made. We hope that the next decade will be a period in which applied LC/DC research is just as exciting.