Dendritic cells are highly specialized, highly efficient, antigen-presenting cells. The precise lineage and membrane markers that identify DC is presently an area of active re-search and much debate. Although dendritic cells were originally thought be of myeloid lineage, recent evidence indicates that a subset of dendritic cells is of lymphoid lineage. Given the correct culture and cytokine conditions, early thymic precursors can develop into DC. DC are believed to express high levels of HLA-DR and several other markers, including CD11c, CD123, CD40, CD54, CD58, CD86, and CD83. Interest in APC has been increased by their use in cancer therapy. DC-based cancer immunotherapy involves isolating DC, loading them with antigen ex vivo, and reinfusing them into patients. CD4+ CD8+ T-cell responses and NK-based antitumor responses were generated. Preliminary clinical trials using this strategy to treat B-cell lymphomas and prostate cancer have been successful.