T cells contribute to immunotherapy and autoimmune pathogenesis and Langerhans cells (LCs) have a substantial ability to activate T cells. In vitro-generated monocyte-derived LCs (Mo-LCs) are useful models to study LC function in autoimmune diseases and to test future LC-based immunotherapies. Although dendritic cells (DCs) expressing high levels of Delta-like 4 (DLL4+ DCs), which is a member of the Notch ligand family, have greater ability than DLL4− DCs to activate T cells, the induction method of human DLL4+ DCs has yet to be determined. The aim of this study is to establish whether Mo-LCs express DLL4 and establish the induction method of antigen presenting cells, which most potently activate T cells, similar to our previously established induction method of human Mo-LCs. We compared the ratios of DLL4 expression and T cell activation via flow cytometry among monocyte-derived cells, which have a greater ability than the resident cells to activate T cells. Here, we discovered that Mo-LCs expressed DLL4, which most potently activated T cells among monocyte-derived cells, and that Mo-LCs and DLL4 expression were induced by DLL4, granulocyte macrophage colony-stimulating factor, and transforming growth factor-β1. Additionally, peptidoglycan was required for DLL4 expression, whereas interleukin-4 repressed it. These findings provide insights into the roles of DLL4-expressing cells such as DLL4+ Mo-LCs in human diseases, which will assist with the development of more effective therapeutic strategies in the future.

Recent studies have highlighted the pathogenic roles of IL-17-producing CD8+ T cells (T-cytotoxic 17 [Tc17]) in psoriasis. However, the underlying mechanisms of Tc17 induction remain unclear. In this study, we focused on the pathogenic subsets of Th17 and their mechanism of promotion of Tc17 responses. We determined that the pathogenic Th17-enriched fraction expressed melanoma cell adhesion molecule (MCAM) and CCR6, but not CD161, because this subset produced IL-17A abundantly and the presence of these cells in the peripheral blood of patients has been correlated with the severity of psoriasis. Intriguingly, the serial analysis of gene expression revealed that CCR6+MCAM+CD161-CD4+ T cells displayed the gene profile for adaptive immune responses, including CD83, which is an activator for CD8+ T cells. Coculture assay with or without intercellular contact between CD4+ and CD8+ T cells showed that CCR6+MCAM+CD161-CD4+ T cells induced the proliferation of CD8+ T cells in a CD83-dependent manner. However, the production of IL-17A by CD8+ T cells required exogenous IL-17A, suggesting that intercellular contact via CD83 and the production of IL-17A from activated CD4+ T cells elicit Tc17 responses. Intriguingly, the CD83 expression was enhanced in the presence of IL-15, and CD83+ cells stimulated with IL-1β, IL-23, IL-15, and IL-15Rα did not express FOXP3. Furthermore, CCR6+MCAM+CD161-CD4+ T cells expressing CD83 were increased in the peripheral blood of patients, and the CD83+ Th17-type cells accumulated in the lesional skin of psoriasis. In conclusion, pathogenic MCAM+CD161- Th17 cells may be involved in the Tc17 responses via IL-17A and CD83 in psoriasis.

Angiotensin III (Ang III) is a heptapeptide derived from Ang II that has been confirmed as the preferred agonist of angiotensin II type 2 receptor (AT2R). Recent studies have revealed AT2R mainly exerts anti-inflammation effects. However, the effects of the Ang III/AT2R pathway on adipocytes remain unknown. Here, the effects of Ang III on glucose uptake were examined. The results showed that AT2R expression was upregulated during adipogenesis in 3T3-L1 preadipocytes, whereas AT1R expression was diminished. Also, Ang III (10 nM) significantly increased glucose uptake by 3T3-L1 adipocytes, which was blocked by PD123319, an AT2R blocker, but not by irbesartan, an AT1R blocker. Ang III also induced the expression of glucose transporter type 1 (GLUT1). These stimulatory effects were inhibited by pretreatment with PD123319, but not with irbesartan. Together, these results indicate that Ang III enhances glucose uptake by upregulating GLUT1 expression via AT2R.

Monocyte-derived Langerhans cell-like dendritic cells （Mo-LCs） are involved in epidermal disorders such as psoriasis in murine models. However, the roles of Mo-LCs in the pathogenesis of psoriasis in humans remain unclear. Also, the contribution of notch ligand delta-like 1 （DLL-1）, expressed on keratinocytes, to Mo-LC functions requires clarification. Here, we established a new method of stimulating Mo-LCs derived from CD14＋ monocytes with immobilized human DLL-1 to generate induced Mo-LCs （DI（＋）Mo-LCs）. The DI（＋）Mo-LCs were compared to the dendritic cells derived from monocytes （Mo-DCs） cultured with interleukin-4 （IL-4） and granulocyte-macrophage colony-stimulating factor （GM-CSF）, and M1 macrophages （Mφ） derived from monocytes cultured with GM-CSF. The DI（＋）Mo-LCs were found to produce significant amounts of IL15, IL23A, and interferon-β （IFNB1） in response to the Toll-like receptor （TLR）3 agonist Polyinosinic-polycytidylic acid （Poly（I:C）） or TLR4 agonist lipopolysaccharide （LPS） despite their low expression of tumor necrosis factor （TNF）. In conclusion, we have established a new method to generate DI（＋）Mo-LCs. We have also discovered that DI（＋）Mo-LCs have a unique capacity for producing IL15 and IL23A, which are related to the pathogenesis of psoriasis. Our data contribute to a better understanding of the roles of Mo-LCs in epidermal defense and pathogenesis.

Although antigen-specific T helper (Th) cells are developed from naive T cells, human Th17 cells are not derived from naive CD4+ T cells unlike murine cells. Therefore, the source of human Th17 cells has remained unresolved. In this study, we assessed the early differentiation pathway of human Th17 cells from CD31+ thymic naive T cells into stem cell memory CCR6+ Th17 precursors and the regulation of this process by cytokines. Peripheral blood mononuclear cells were isolated from healthy volunteers. We found that only CD31- CCR6+ naive type CD4+ T cells had the ability to produce IL-17A in response to Th17-inducing stimuli. A cell tracking assay using CD31+ CCR6- cells labeled with carboxyfluorescein diacetate succinimidyl ester revealed that CD31- CCR6+ Th17 precursors were derived from CD31+ CCR6- thymic naive T cells. CD31 is known to suppress IL-17 production by interfering with downstream T cell receptor (TCR) signaling molecules including Lck, which is essential for IL-17 production. The inactive form of Lck was much higher in CD31+ T cells than CD31- T cells after TCR stimulation. In experiments of cytokine-mediated modulation of Th17 cell differentiation, IL-4 suppressed the conversion of CD31+ CCR6- naive T cells into CD31- CCR6+ Th17 precursors by upregulating CD31 expression and suppressing CCR6 expression. In conclusion, CD31- CCR6+ Th17 precursors could be sourced from CD31+ CCR6- naive T cells, and IL-4 regulated the early Th17 differentiation. Our findings provide novel insights into the regulation of differentiation of naive CD4+ T cells into Th17 cells in humans. Furthermore, our results may provide hints for further elucidation of the differentiation process of Th17 cells and of the pathology of Th17 cell-related diseases.