The mucosal factors retinoic acid and TGF-β1 induce phenotypically and functionally distinct dendritic cell types.

Non-inflammatory dendritic cell (DC) subsets play an essential role in preventing massive inflammation in mucosal tissues. We investigated whether mucosa-related factors, namely retinoic acid (RA) and transforming growth factor-β (TGF-β1), can induce such DC types. DCs were differentiated from monocytes in the absence or presence TGF-β1 and RA. The phenotype as well as responsiveness to bacterial ligands was studied in detail. Compared to monocyte-derived DCs (moDCs), the expression of co-stimulatory molecule CD86 and DC maturation marker CD83 were strongly reduced by RA and TGF-β1. In addition, both RA- and TGF-β1-induced DCs showed strongly decreased responsiveness to stimulation with the bacterial ligands lipopolysaccharide and peptidoglycan, and produced significantly lower levels of the pro-inflammatory cytokines IL-12 and TNF-α compared to moDCs, whilst IL-10 production was not significantly reduced. DCs differentiated under the influence of RA uniquely expressed markers related to intestinal homing (CD103 and integrin β7). In addition, CCR7, which mediates homing to lymph nodes, was expressed by DCs differentiated in the presence of RA, and also to a lesser extent by the other DC types. Furthermore, whereas moDCs and TGF-β1-derived moDCs expressed high levels of CD32, RA-derived DCs lacked CD32 expression but expressed high levels of CD64, suggesting that RA-DCs may primarily respond to soluble proteins and moDCs, and TGF-β DCs to immune complexes. The data presented here support the hypothesis that the mucosal factors TGF-β1 and RA, which can also be provided through dietary intake of dairy products, result in functionally and phenotypically distinct DC types with non-inflammatory properties.

den Hartog G ，van Altena C ，Savelkoul HF ，van Neerven RJ ... -  《-》

Differential regulation of CD103 (αE integrin) expression in human dendritic cells by retinoic acid and Toll-like receptor ligands.

CD103 (αE integrin) is an important dendritic cell (DC) marker that characterizes functionally distinct DC subsets in mice and humans. However, the mechanism by which CD103 expression is regulated in human DCs and the role of CD103 for DC function are not very well understood. Here, we show that retinoic acid (RA) treatment of human monocyte-derived DCs (MoDCs) increased the ability of the DCs to synthesize RA and induced MoDC expression of CD103 and β7 at the mRNA and protein level. In contrast, RA was unable to induce the expression of CD103 in primary human DCs isolated from the gastric mucosa. Inhibition of TGF-β signaling in MoDCs down-regulated RA-induced CD103 expression, indicating that TGF-β-dependent pathways contribute to the induction of CD103. Conversely, when RA-treated MoDCs were stimulated with live Helicobacter pylori, commensal bacteria, LPS, or a TLR2 agonist, the RA-induced up-regulation of CD103 and β7 integrin expression was completely abrogated. To determine whether CD103 expression impacts DC priming of CD4+ T cells, we next investigated the ability of CD103+ and CD103─ DCs to induce mucosal homing and T cell proliferation. Surprisingly, RA treatment of DCs enhanced both α4β7 expression and proliferation in cocultured T cells, but no difference was seen between RA-treated CD103+ and CD103─ DCs. In summary, our data demonstrate that RA, bacterial products, and the tissue environment all contribute to the regulation of CD103 on human DCs and that DC induction of mucosal homing in T cells is RA dependent but not CD103 dependent.

Roe MM ，Swain S ，Sebrell TA ，Sewell MA ，Collins MM ，Perrino BA ，Smith PD ，Smythies LE ，Bimczok D ... -  《-》

Cryopreservation of monocytes or differentiated immature DCs leads to an altered cytokine response to TLR agonists and microbial stimulation.

Literature on the effects of cryopreservation and thawing of monocytes or monocyte-derived immature dendritic cells (iDCs) on the subsequent functional capacities of the DCs is limited to a few specific maturation stimuli and is focused on applications in clinical immunotherapy. Given the cardinal role of DCs in regulating tolerance and immunity at mucosal surfaces there is a growing interest in understanding the effect of stromal, microbial and probiotic signals on DC function. Therefore our aim was to investigate the effects of cryopreservation on the functional properties of DCs stimulated with bacteria or the bacterial components using a standardized method. Surface markers CD83 and CD86 were expressed at similar levels on iDCs generated from cryopreserved or freshly isolated monocytes. Cryopreservation of iDCs led to slightly decreased expression of CD86 and CD83 compared to freshly generated iDCs prepared from unfrozen cells but this did not affect the capacity of DCs to acquire fully mature characteristics after stimulation. In contrast the cytokine response to lipoteichoic acid and bacterial stimulation was altered by cryopreservation of monocytes or iDCs, particularly for IL-12p70 which was decreased up to 250 fold or not detected. Cryopreservation also decreased TNF-α and IL-1β production in stimulated iDCs but to a lesser extent than for IL-12p70, depending on the maturation factors used. The amounts of IL-10 produced by stimulated iDCs were increased up to 3.6 fold when iDCs were cryopreserved, but decreased up to 90 fold when generated from cryopreserved monocytes. Immature DCs are often used to investigate the immunomodulatory properties of probiotics and here we show for the first time that cryopreserved monocytes and cryopreserved iDCs have a skewed cytokine response to microbial stimulation. These findings have implications for the methods used in bacterial-DC immune assays and highlight the importance of comparing different cytokines and stimuli in immune cell cryopreservation protocols.

Meijerink M ，Ulluwishewa D ，Anderson RC ，Wells JM ... -  《-》

In vitro treatment of human transforming growth factor-beta1-treated monocyte-derived dendritic cells with haptens can induce the phenotypic and functional changes similar to epidermal Langerhans cells in the initiation phase of allergic contact sensitivi

Aiba S ，Manome H ，Yoshino Y ，Tagami H ... -  《-》

Retinoic acid prevents mesenteric lymph node dendritic cells from inducing IL-13-producing inflammatory Th2 cells.

Yokota-Nakatsuma A ，Takeuchi H ，Ohoka Y ，Kato C ，Song SY ，Hoshino T ，Yagita H ，Ohteki T ，Iwata M ... -  《-》