IL-34 is a recently identified cytokine that signals via the M-CSF receptor and promotes monocyte survival. Depending on the environment, monocytes can differentiate into macrophages (Mφ) or dendritic cells (DC). A wide spectrum of Mφ and DC subsets, with distinct phenotypes and functions, has been described. To date, the phenotype of monocytes exposed to IL-34 remains unexplored. We report here that IL-34 induces the differentiation of monocytes into CD14high CD163high CD1a− Mφ (IL-34-Mφ). Upon LPS stimulation, IL-34-Mφ exhibit an IL-10high IL-12low M2 profile and express low levels of the costimulatory molecules CD80 and CD86. IL-34-Mφ exhibit poor T cell costimulatory properties, and have potent immunosuppressive properties (decrease of TCR-stimulated T cell proliferation). For all the parameters analyzed, IL-34-Mφ are phenotypically and functionally similar to M-CSF-Mφ. IL-34 appears as efficient as M-CSF in inducing the generation of immunosuppressive Mφ. Moreover, the generation of IL-34-Mφ is mediated through the M-CSF receptor, is independent of endogenous M-CSF consumption and is potentiated by IL-6. In an attempt to identify strategies to prevent a deleterious M2 cell accumulation in some pathological situations, we observed that IFNγ and GM-CSF prevent the generation of immunosuppressive Mφ induced by IL-34. IFNγ also switches established IL-34-Mφ into immunostimulatory Mφ. In conclusion, we demonstrate that IL-34 drives the differentiation of monocytes into immunosuppressive M2, in a manner similar to M-CSF, and that IFNγ and GM-CSF prevent this effect.

Chronic hepatitis C virus (HCV) infection is characterized by progressive hepatic fibrosis, a process dependent on monocyte recruitment and accumulation into the liver. The mediators expressed in chronically injured liver that control the differentiation of human monocytes into profibrotic macrophages (Mu) remain poorly defined. We report that chronically HCV-infected patients with high fibrosis stages have higher serum levels of macrophage colony-stimulating factor (M-CSF) and interleukin (IL)234 than HCV-infected patients with lower fibrosis stages and healthy subjects. Immunohistochemistry reveals an intense expression of IL-34 and M-CSF by hepatocytes around liver lesions. In addition, HCV infection and inflammatory cytokines enhance the in vitro production of IL-34 and M-CSF by hepatocytes. We next analyzed the acquisition of profibrotic properties by Mu generated with M-CSF (M-CSF-Mu) or IL-34 (IL-34-Mu). M-CSF and IL-34 up-regulate the expression, by differentiating monocytes, of chemokine (C-C motif) ligand (CCL)2, CCL4, C-C chemokine receptor (CCR)1, and CCR5, which are involved in monocyte recruitment/Mu accumulation in liver lesions. M-CSF-Mu and IL-34-Mu also express the hepatic stellate cell (HSC) activators, platelet-derived growth factor, transforming growth factor beta, and galectin-3. IL-34-Mu and M-CSF-Mu induce type I collagen synthesis by HSCs, the main collagen-producing cells in liver fibrosis. IL-13, whose expression correlates with the fibrosis stage in HCV-infected patients, decreases the expression of the collagenase, matrix metalloproteinase 1, by IL-34-Mu and M-CSF-Mu, thereby enhancing collagen synthesis. By inhibiting the production of interferon-gamma (IFN-c) by activated natural killer cells, IL-34-Mu and M-CSF-Mu prevent the IFN-c-induced killing of HSCs. Conclusion: These results identify M-CSF and IL-34 as potent profibrotic factors in HCV liver fibrosis.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers with very few available treatments. For many decades, gemcitabine was the only treatment for patients with PDAC. A recent attempt to improve patient survival by combining this chemotherapy with FOLFIRINOX and nab-paclitaxel failed and instead resulted in increased toxicity. Novel therapies are urgently required to improve PDAC patient survival. New treatments in other cancers such as melanoma, non-small-cell lung cancer, and renal cancer have emerged, based on immunotherapy targeting the immune checkpoints cytotoxic T-lymphocyte-associated antigen 4 or programmed death 1 ligand. However, the first clinical trials using such immune checkpoint inhibitors in PDAC have had limited success. Resistance to immunotherapy in PDAC remains unclear but could be due to tissue components (cancer-associated fibroblasts, desmoplasia, hypoxia) and to the imbalance between immunosuppressive and effector immune populations in the tumor microenvironment. In this review, we analyzed the presence of “good and bad immunological cops” in PDAC and discussed the significance of changes in their balance.

Macrophages orchestrate the immune response via the polarization of CD4+ T helper GM-CSF macrophages promote Th1 cells. The polarization of memory T cells into Th17 cells is mediated via membrane IL-1α (mIL-1α), which is constitutively expressed by M-CSF-, IL-34 macrophages, andTAMs. This study elucidates a new mechanism that allows macrophages to maintain locally restrained and smoldering inflammation, which is required in angiogenesis and metastasis.Keywords: IL-34 r IL-1α r Inflammation r Macrophages r M-CSF r Th17 cellsAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionMacrophages have a central role in numerous physiological processes, such as control of infection, wound healing, inflammation, and tissue homeostasis. Tissues-resident macrophages (such as Correspondence: Dr. Pascale Jeannin e-mail: pascale.jeannin@univ-angers.fr microglia, Kupffer cells, and osteoclasts) are found in connective tissues and in every organ in the body [1]. Moreover, upon danger signals, monocytes are rapidly recruited and differentiate into macrophages [1]. Cells of the monocyte-macrophage lineage are characterized by remarkable plasticity and diversity * These authors contributed equally to this work. In human, three cytokines, GM-CSF, M-CSF, and IL-34, promote monocyte survival and differentiation into macrophages [4]. Macrophages generated in the presence of GM-CSF (GM-CSF macrophages) produce IL-12, IL-23, and proinflammatory cytokines, but low levels of . They exhibit T-cell costimulatory, antitumoral, and microbicidal properties [2]. GM-CSF macrophages are usually referred to as M1 cells (even in the absence of IFN-gamma stimulation). IL-34 and M-CSF, which signal via the M-CSF receptor (c-fms or CD115), induce the differentiation of human monocytes into macrophages with closely similar phenotypes [6]. These macrophage subsets are IL-10 high low cells that do not produce IL-23 and express low levels of CD80, and CD86 [6,7]. M-CSF-and IL-34 macrophages exhibit low T-cell costimulatory properties and dampen the activity of effector T cells [6,7]. In solid tumors, tumor-associated macrophages (TAMs) are the most abundant immunosuppressive leukocytes in the tumor microenvironment and, in numerous cancers, their density is correlated with a poor prognosis [3]. In addition to immunoregulatory properties, TAMs favor angiogenesis and promote tumorcell progression and metastasis [3]. In previous studies, we have shown that + Treg cells, have been described [14,17]. As we suspected that M-CSF-and IL-34 macrophages should favor the switch of memory T cells into Treg cells, we analyzed the expression of some Treg-associated markers by Th17 cells generated in the presence of M-CSF-and IL-34 macrophages. These Th17 cells expressed CCR4, CCR6, and CD161, but not TGF-β, CD39, CD73, IL-10, and FoxP3 (Table 1 and Supporting Information Fig. 2). In contrast, these cells express the mRNA encoding CCR6 (Fig. 2B) and IL-21 (Fig. 2C), two markers of conventional Th...

Vγ9Vδ2 T cells are anti-tumor immune effectors of growing interest in cancer including Pancreatic Ductal Adenocarcinoma (PDAC), an especially aggressive cancer characterized by a hypoxic and nutrient-starved immunosuppressive microenvironment. Since Butyrophilin 3 A (BTN3A) isoforms are critical activating molecules of Vγ9Vδ2 T cells, we set out to study BTN3A expression under both basal and stress conditions in PDAC primary tumors, and in novel patient-derived xenograft and PDAC-derived cell lines. BTN3A2 was shown to be the most abundant isoform in PDAC and was stress-regulated. Vγ9Vδ2 T cells cytolytic functions against PDAC required BTN3A and this activity was strongly enhanced by the agonist anti-BTN3A 20.1 mAb even under conditions of hypoxia. In PDAC primary tumors, we established that BTN3A expression and high plasma levels of soluble BTN3A were strongly associated with a decreased survival. These findings may have important implications in the design of new immunotherapeutic strategies that target BTN3A for treating PDAC.

A better characterization of T-cell subsets in the microenvironment of classical Hodgkin lymphoma (cHL) would help to develop immunotherapies. Using multicolor flow cytometry, we identified in 6 of 43 cHL tissue samples a previously unrecognized subset of CD8 T cells coexpressing CXCR5 and inducible T-cell costimulator (ICOS) molecules (CD8). These cells shared phenotypic features with follicular helper T (T) cells including low CCR7 expression together with high expression of B-cell lymphoma-6, programmed cell death 1, B and T lymphocyte attenuator, CD200, and OX40. They had deficient cytotoxicity, low interferon-γ secretion, and common functional properties with intratumoral CD4 T cells, such as production of interleukin-4 (IL-4), IL-21, CXCL13, and capacity to sustain B cells. Gene profiling analysis showed a significant similarity between the signatures of CD8 T cells and CD4 T cells. Benign lymphadenitis tissues (n = 8) were devoid of CD8 cells. Among the 35 B-cell lymphoma tissues analyzed, including follicular lymphomas (n = 13), diffuse large cell lymphomas (n = 12), marginal zone lymphomas (MZLs; n = 3), mantle cell lymphomas (n = 3), and chronic lymphocytic leukemias (n = 4), only 1 MZL sample contained CD8 cells. Lymphoma tumors with CD8 cells shared common histopathological features including residual germinal centers, and contained high amounts of activated CD8 cells. These data demonstrate a CD8 T-cell differentiation pathway leading to the acquisition of some T similarities. They suggest a particular immunoediting process with global CD8 activation acting mainly, but not exclusively, in HL tumors.

In diffuse large B-cell lymphoma (DLBCL), tumor-infiltrating T lymphocytes (TILs) are involved in therapeutic responses. However, tumor-specific TILs can be dysfunctional, with impaired effector functions. Various mechanisms are involved in this exhaustion, and the increased expression of programmed cell death receptor 1 (PD1) and TIM3 on dysfunctional cells suggests their involvement. However, conflicting data have been published regarding their expression or coexpression in DLBCL. We evaluated the presence and phenotype of CD4+ and CD8+ TILs in freshly collected tumor tissues in DLBCL and compared the results with those in follicular lymphoma, classical Hodgkin lymphoma, and nonmalignant reactive lymphadenopathy. We found that TILs expressing both PD1 and TIM3 were expanded in DLBCL, particularly in the activated B cell–like subgroup. Isolated PD1+TIM3+ TILs exhibited a transcriptomic signature related to T-cell exhaustion associated with a reduction in cytokine production, both compromising the antitumor immune response. However, these cells expressed high levels of cytotoxic molecules. In line with this, stimulated PD1+TIM3+ TILs from DLBCL patients exhibited reduced proliferation and impaired secretion of interferon-γ, but these functions were restored by the blockade of PD1 or TIM3. In summary, the PD1+TIM3+ TIL population is expanded and exhausted in DLBCL but can be reinvigorated with appropriate therapies.

AT2R-dependent interleukin-17 production by T lymphocyte is necessary for collateral artery growth and could represent a new therapeutic target in ischaemic disorders.