The bloodline of CD8α+ dendritic cells

The immune system is highly coordinated by various cell types. Dendritic cells (DCs) orchestrate immune responses at various stages and bridge innate immunity and adaptive immunity. DCs are a family of cells consisting of various subsets distinguished by surface markers, locations, and transcription factors that govern their development, differentiation, and homeostasis. The complexity of DC subset biology has hindered the understanding of the functional differences among DC subsets. The subset expressing the surface molecule CD8 alpha is of particular interest, due to the efficiency of this DC subset in priming CD8(+) cytotoxic T cells and cross-presenting exogenous antigens to CD8(+) T cells. CD8 alpha (+) DCs maintain tolerance to autologous antigens at steady state, but when activated secrete IL-12, polarizing T helper (Th) 1 responses. Recently, novel DC subsets were found to be present in peripheral tissues and the relationship between CD8 alpha(+) DCs in lymphoid organs and DC subsets in peripheral tissues has been revealed. This review describes the pedigree of CD8 alpha (+) DCs and related subsets, including a history of the discovery of DC subsets and their functional characterization.