The characterization of human dendritic cell (DC) subsets is essential for the design of new vaccines. We report the first detailed functional analysis of the human CD141+ DC subset. CD141+ DCs are found in human lymph nodes, bone marrow, tonsil, and blood, and the latter proved to be the best source of highly purified cells for functional analysis. They are characterized by high expression of toll-like receptor 3, production of IL-12p70 and IFN-β, and superior capacity to induce T helper 1 cell responses, when compared with the more commonly studied CD1c+ DC subset. Polyinosine-polycytidylic acid (poly I:C)–activated CD141+ DCs have a superior capacity to cross-present soluble protein antigen (Ag) to CD8+ cytotoxic T lymphocytes than poly I:C–activated CD1c+ DCs. Importantly, CD141+ DCs, but not CD1c+ DCs, were endowed with the capacity to cross-present viral Ag after their uptake of necrotic virus-infected cells. These findings establish the CD141+ DC subset as an important functionally distinct human DC subtype with characteristics similar to those of the mouse CD8α+ DC subset. The data demonstrate a role for CD141+ DCs in the induction of cytotoxic T lymphocyte responses and suggest that they may be the most relevant targets for vaccination against cancers, viruses, and other pathogens.

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We recently demonstrated that three antigen-presenting cell (APC) subsets exist in the healthy human dermis, CD14(+) and CD1a(+) dermal APCs and migratory dermal Langerhans cells. Here, we extend these findings by defining CD208 as an exclusive marker of migratory dermal Langerhans cells, confirming that migratory dermal Langerhans cells (CD1a(high) CD207(+) CD208(+)) and CD1a(+) dermal APCs (CD1a(mid) CD207(-) CD208(-)) are two distinct APC populations. Using flow cytometry and multicolor fluorescence immunohistochemistry, we demonstrated that there were striking differences between CD1a(+) and CD14(+) dermal APCs in their expression of pattern recognition receptors and maturation markers. Expression of Toll-like receptor (TLR) 2, CD206 and CD209 was largely restricted to CD14(+) dermal APCs. Consistent with these observations, most CD14(+) dermal APCs expressed an immature phenotype when compared with CD1a(+) dermal APCs, which expressed high levels of the maturation marker CD83 on their cell surface. However, a subset of CD14(+) dermal APCs also expressed cell-surface CD83, associated with a loss of cell-surface TLR2, suggesting that they have the capacity to mature. CD14(+) dermal APCs are therefore the dominant cutaneous APC population capable of sensing ligands recognized by CD206, CD209 and TLR2 and subsequently may have the potential to mature. CD68 expression was largely restricted to a subset of CD14(+) dermal APCs, while both CD14(+) and CD1a(+) dermal APCs expressed CD11b and CD11c. These findings have important implications for understanding cutaneous immune responses in humans and for the optimization of vaccine delivery via the skin.

5,6-Dimethylxanthenone-4-acetic acid (DMXAA) acts through tumor vascular disruption and cytokine production and is the first of its class to enter phase 3 trials. We characterized leukocytes and cytokines in murine Colon 38 tumors before and after DMXAA treatment. Tumor mass declined 50% 24 hours after DMXAA administration, but the leukocyte count per gram of tumor increased threefold owing to a large influx of Ly6G(+)CD11b(+)F4/80(-) cells with the morphology of neutrophils. However, B and T lymphocytes, natural killer cells, and macrophages in the tumor all decreased in numbers. Seven chemokines were substantially induced in the tumor, spleen, and serum 4 hours after DMXAA administration. Using cultured spleen cell subpopulations, CD11b(+) cells (largely monocytes and macrophages) were shown to be the primary producers of tumor necrosis factor alpha, interleukin 6 (IL-6), and macrophage inflammatory 1alpha (MIP-1alpha). CD49b(+) natural killer cells produced IP-10, whereas CD45R(+) B lymphocytes produced regulated upon activation normal T cell express sequence. T lymphocytes were not major producers of cytokines in the response to DMXAA. Murine peripheral blood leukocytes (PBLs) produced a similar panel of cytokines in culture to that detected in mouse serum after DMXAA treatment. Cytokines in human PBL cultures were subsequently measured with the aim of identifying potential serum markers of the human response to DMXAA. IP-10 (P < .001), monocyte chemoattractant protein 1 (P < .001), and sCD40L (P < .01) were decreased, whereas IL-8 (P < .001) and MIP-1alpha (P = .03) were increased in DMXAA-treated compared with untreated PBL cultures from a group of 12 donors.