Dendritic cells and their clinical applications

The key role dendritic cells (DC) play in initiating primary (and probably secondary) immune responses is now well recognised. There is still much uncertainty as to how to define DC, as it now appears that there may be several different DC differentiation pathways giving rise to subsets of DC, which have different phenotypic and functional properties (1). Thus, there are epithelial and interstitial associated subsets of DC (2). The monocyte derived DC (Mo-DC) is distinguished from these DC types on both molecular and functional criteria (3). There is also data derived from mouse studies to indicate that DC may be derived from both myeloid and lymphoid precursors (4) and that the former cells are generally immunostimulatory, whereas the lymphoid precursor-derived DC may exert an alternative negative regulatory function. The molecular bases whereby the myeloid DC responds to danger signals and takes up antigen, prior to migrating to the lymph nodes to interact with T lymphocytes, is slowly being unravelled. Undoubtedly, DC play a major role in immunological events. Indeed, there is data to suggest that abnormal DC function contributes to the progress of human malignancies (5) and now some of the encouraging animal data using DC based vaccines for clinical cancer immunotherapy.