Transcriptional analyses show that mouse bone marrow-derived DC and human monocyte-derived DC are indistinguishable from macrophages. Clustering of cell subsets based upon their global gene expression profiles. In panels “(a)” and “(b)” Pearson correlation matrices were prepared by comparing the microarray data sets derived from all samples used in each study ([11] and [105], resp.). Graphs were then constructed using only those sample-to-sample relationships greater than r = 0.9 and clustered with an MCL inflation value of 2.2. Each node represents an individual microarray data set and the edges are coloured on a sliding scale according to the strength of the correlation (red, r = 1.0; blue, r = 0.9). Each cluster of samples was assigned a different colour. Each of these analyses shows that at the transcriptomic level the in vitro bone marrow-derived DC (BMDC) or monocyte-derived DC (MDDC) prepared from mice (panel “(a)”) and humans (panel “(b)”) are indistinguishable from macrophages and do not cluster with conventional DC enriched from tissues such as the spleen, tonsils, or peripheral blood. The tissue DC, BMDC, and MDDC data sets are highlighted in red font. Reference [11] provides full details about the sources of all the 304 individual microarray data sets used in “(a).” Reference [105] provides full details about the sources of all the 745 microarray data sets used in “(b).” BMDC, bone marrow-derived dendritic cells; BMDM, bone marrow-derived macrophage; anthrax, Bacillus anthracis edema toxin; CMP, common myeloid progenitors; ES, embryonic stem cell; GMP, granulocyte monocyte progenitors; HSC, haematopoietic stem cell; IKDC, interferon-producing killer DC; MDDC, monocyte-derived DC; MDM, monocyte-derived macrophage; MEP, megakaryocyte-erythroid progenitor cell; MkP, megakaryocyte progenitors; MSC, mesenchymal stem cells; NK, natural killer; PreCFU-E, preerythroid progenitors; PreMegE, premegakaryocyte/erythroid; PB, peripheral blood; Treg, regulatory T cell. Panel “(a)” is reproduced from [11] with permission from Elsevier. Panel “(b)” is reproduced from [105] under the terms of the Creative Commons Attribution License 2.0.