Development of CD8 alpha-positive dendritic cells from a common myeloid progenitor

Dendritic cells (DCs) are critical in both initiating adaptive immune respo nses and maintaining tolerance to self antigens. These apparently contradic tory roles have been suggested to depend on different subsets of DCs that a rise from either myeloid or Lymphoid hematopoietic origins, respectively, A lthough DC expression of CD8 alpha is attributed to a lymphoid origin, here we show that both CD8 alpha (+) and CD8 alpha (-) DCs can arise from clono genic common myeloid progenitors in both thymus and spleen. Thus, expressio n of CD8 alpha is not indicative of a lymphoid origin, and phenotypic and f unctional differences among DC subsets are likely to reflect maturation sta tus rather than ontogeny.