Dendritic cell populations of the spleen, the lymph nodes, and the thymus. (A) DCs were purified in parallel from spleens, thymi, and subcutaneous LNs and analyzed by FACS using antibodies for CD11c, MHC II, and the following combinations depending on the particular lymphoid organ: CD8 and CD4 (spleen), CD8 and CD205 (LN), or only CD8 (thymus). The plots shown were obtained by gating on the CD11c⁺ live cells (PI^–) in each preparation. Mouse spleens contain 3 populations of CD11c⁺ DCs that can be distinguished by their expression of CD4 and CD8. Subcutaneous LNs contain similar populations (the CD4⁺ and CD4^–CD8^– DCs are both CD205^–) and, in addition, epDCs. The thymus DCs have a more homogeneous phenotype. The histograms at the bottom of each plot show the expression of MHC II in all the DCs (the numbers indicate the percentages of MHC II^hi DCs). The dashed line shows the fluorescent level of unstained cells. The 3 smaller histograms at the right side show the expression of MHC II in each of the subcutaneous LN DC populations. Note that the occurrence of MHC II^high DCs in the subcutaneous LNs can be attributed almost entirely to the presence of epDCs. The 3 splenic DC populations expressed comparable levels of MHC II. All the results were obtained in parallel using the same MHC II antibody and are representative of multiple experiments. (B) The DCs from the subcutaneous LNs, mesenteric LNs, iliac LNs, and mediastinal LNs were purified and analyzed in parallel as in (A). The number in the plots indicates the percentage of epDCs in each LN. In all cases, the CD205^–CD8^– and the CD205⁺CD8⁺ DCs expressed low levels of MHC II, whereas the epDCs accounted for most of the MHC II^high DCs. Note that overlapping populations obscure the distinction between MHC II^low and MHC II^high DCs in the gated histograms. The results shown are representative of at least 2 experiments.