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Imaging mass cytometry (IMC) enables the in situ analysis of in-depth-phenotyped cells in their native microenvironment within the preserved architecture of a single tissue section. To date, it permits the simultaneous analysis of up to 50 different protein- markers targeted by metal-conjugated antibodies. The application of IMC in the field of cancer research may notably help 1) to define biomarkers of prognostic and theragnostic significance for current and future treatments against well-established and novel therapeutic targets and 2) to improve our understanding of cancer progression and its resistance mechanisms to immune system and how to overcome them. In the present article, we not only provide a literature review on the use of the IMC in cancer-dedicated studies but we also present the IMC method and discuss its advantages and limitations among methods dedicated to deciphering the complexity of cancer tissue., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Le Rochais, Hemon, Pers and Uguen.)

The integrative analysis of tumor immune microenvironment (TiME) components, their interactions and their microanatomical distribution is mandatory to better understand tumor progression. Imaging Mass Cytometry (IMC) is a high dimensional tissue imaging system which allows the comprehensive and multiparametric in situ exploration of tumor microenvironments at a single cell level. We describe here the design of a 39-antibody IMC panel for the staining of formalin-fixed paraffin-embedded human tumor sections. We also provide an optimized staining procedure and details of the experimental workflow. This panel deciphers the nature of immune cells, their functions and their interactions with tumor cells and cancer-associated fibroblasts as well as with other TiME structural components known to be associated with tumor progression like nerve fibers and tumor extracellular matrix proteins. This panel represents a valuable innovative and powerful tool for fundamental and clinical studies that could be used for the identification of prognostic biomarkers and mechanisms of resistance to current immunotherapies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Elaldi, Hemon, Petti, Cosson, Desrues, Sudaka, Poissonnet, Van Obberghen-Schilling, Pers, Braud, Anjuère and Meghraoui-Kheddar.)

Our knowledge and control of the pathogenesis induced by the filariae remain limited due to experimental obstacles presented by parasitic nematode biology and the lack of selective prophylactic or curative drugs. Here we thought to investigate the role of neutrophils in the host innate immune response to the infection caused by the Litomosoides sigmodontis murine model of human filariasis using mice harboring a gain-of-function mutation of the chemokine receptor CXCR4 and characterized by a profound blood neutropenia (Cxcr4(+/1013)). We provided manifold evidence emphasizing the major role of neutrophils in the control of the early stages of infection occurring in the skin. Firstly, we uncovered that the filarial parasitic success was dramatically decreased in Cxcr4(+/1013) mice upon subcutaneous delivery of the infective stages of filariae (infective larvae, L3). This protection was linked to a larger number of neutrophils constitutively present in the skin of the mutant mice herein characterized as compared to wild type (wt) mice. Indeed, the parasitic success in Cxcr4(+/1013) mice was normalized either upon depleting neutrophils, including the pool in the skin, or bypassing the skin via the intravenous infection of L3. Second, extending these observations to wt mice we found that subcutaneous delivery of L3 elicited an increase of neutrophils in the skin. Finally, living L3 larvae were able to promote in both wt and mutant mice, an oxidative burst response and the release of neutrophil extracellular traps (NET). This response of neutrophils, which is adapted to the large size of the L3 infective stages, likely directly contributes to the anti-parasitic strategies implemented by the host. Collectively, our results are demonstrating the contribution of neutrophils in early anti-filarial host responses through their capacity to undertake different anti-filarial strategies such as oxidative burst, degranulation and NETosis.

Background & Aims: Kupffer cells (KC) play a key role in the onset of inflammation in non-alcoholic steatohepatitis (NASH). The glucocorticoid receptor (GR) induces glucocorticoid-induced leucine zipper (GILZ) expression in monocytes/macrophages and is involved in several inflammatory processes. We hypothesized that the GR-GILZ axis in KC may contribute to the pathophysiology of obesity-induced liver inflammation., Methods: By using a combination of primary cell culture, pharmacological experiments, mice deficient for the Gr specifically in macrophages and transgenic mice overexpressing Gilz in macrophages, we explored the involvement of the Gr-Gilz axis in KC in the pathophysiology of obesity-induced liver inflammation., Results: Obesity was associated with a downregulation of the Gr and Gilz, and an impairment of Gilz induction by lipopolysaccharide (LPS) and dexamethasone (DEX) in KC. Inhibition of Gilz expression in isolated KC transfected with Gilz siRNA demonstrated that Gilz downregulation was sufficient to sensitize KC to LPS. Conversely, liver inflammation was decreased in obese transgenic mice specifically overexpressing Gilz in macrophages. Pharmacological inhibition of the Gr showed that impairment of Gilz induction in KC by LPS and DEX in obesity was driven by a downregulation of the Gr. In mice specifically deficient for Gr in macrophages, Gilz expression was low, leading to an exacerbation of obesity-induced liver inflammation., Conclusions: Obesity is associated with a downregulation of the Gr-Gilz axis in KC, which promotes liver inflammation. The Gr-Gilz axis in KC is an important target for the regulation of liver inflammation in obesity., (Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

The ectonucleotidases CD39 and CD73 hydrolyze extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to generate adenosine, which binds to adenosine receptors and inhibits T-cell and natural killer (NK)-cell responses, thereby suppressing the immune system. The generation of adenosine via the CD39/CD73 pathway is recognized as a major mechanism of regulatory T cell (Treg) immunosuppressive function. The number of CD39⁺ Tregs is increased in some human cancers, and the importance of CD39⁺ Tregs in promoting tumor growth and metastasis has been demonstrated using several in vivo models. Here, we addressed whether CD39 is expressed by tumor cells and whether CD39⁺ tumor cells mediate immunosuppression via the adenosine pathway. Immunohistochemical staining of normal and tumor tissues revealed that CD39 expression is significantly higher in several types of human cancer than in normal tissues. In cancer specimens, CD39 is expressed by infiltrating lymphocytes, the tumor stroma, and tumor cells. Furthermore, the expression of CD39 at the cell surface of tumor cells was directly demonstrated via flow cytometry of human cancer cell lines. CD39 in cancer cells displays ATPase activity and, together with CD73, generates adenosine. CD39⁺CD73⁺ cancer cells inhibited the proliferation of CD4 and CD8 T cells and the generation of cytotoxic effector CD8 T cells (CTL) in a CD39- and adenosine-dependent manner. Treatment with a CD39 inhibitor or blocking antibody alleviated the tumor-induced inhibition of CD4 and CD8 T-cell proliferation and increased CTL- and NK cell-mediated cytotoxicity. In conclusion, interfering with the CD39-adenosine pathway may represent a novel immunotherapeutic strategy for inhibiting tumor cell-mediated immunosuppression., (©2014 American Association for Cancer Research.)

Homing of inflammatory cells to the liver is key in the progression of non-alcoholic steatohepatitis (NASH). An abnormal response of CD4+ T-cells from obese mice to the chemotactic effect of CXCL12 has been reported but the mechanism involved in this process and relevance in patients are unknown. We aimed to explore the mechanism involved in the abnormal chemotaxis of CXC chemokine ligand 12 (CXCL12) in several mouse models of NASH and the relevance in the context of human non-alcoholic fatty liver disease (NAFLD). We assessed chemotactic responsiveness of CD4+ T-cells to CXCL12, the effect of AMD3100, a CXC chemokine receptor 4 (CXCR4) antagonist, in mice and lymphocytes from patients with NAFLD, and the affinity of CXCL12 for CXCR4. CXCL12-promoted migration of CD4+ T-cells from three different mouse models of NASH was increased and dependent of CXCR4. CD4+ T-cells from patients with NASH, but not from patients with pure steatosis, responded more strongly to the chemotactic effect of CXCL12, and this response was inhibited by AMD3100. Treatment with AMD3100 decreased the number of CD4+ T-cells to the liver in ob/ob mice. CXCL12 expression in the liver, CXCR4 and CXCR7 expression in CD4+ T-cells were not increased in three different mouse models of NASH. However, the affinity of CXCL12 for CXCR4 was increased in CD4+ T-cells of ob/ob mice. In conclusion, the CXCL12/CXCR4 pathway contributes in both mice and patients to the enhanced recruitment of CD4+ T-cells in NASH. An increased affinity of CXCL12 to CXCR4 rather than a higher expression of the chemokine or its receptors is involved in this process.

Ca(2+) signaling is a key regulator of B lymphocyte cell fate and defects in this signaling pathway have been reported in numerous diseases such as Chronic lymphocytic leukemia (CLL). CLL is a B cell clonal disorder characterized by the accumulation of mature monoclonal CD5(+) B cells. Although CLL could be considered to be a proliferative disease, most circulating CLL B cells are arrested in the G0 phase of the cell cycle and present both defects in calcium (Ca(2+)) homeostasis and signaling. The Ca(2+) response to antigen ligation is heterogeneous and related, in part, to defects arising from the incapacity to respond to B cell receptor (BCR) engagement (anergy), to the expression of T cell kinases (e.g. Zap70), and to the presence of negative feedback regulation by phosphatases (e.g. SHP-1). Anergic CD5(+) CLL B cells are characterized by an elevated basal Ca(2+) level, IgM/CD79 downregulation, a constitutive activation of BCR pathway kinases, and an activation of the nuclear factor of activated T cells (NF-AT). Based on the Ca(2+) response, patients are classified into three groups: unresponders, responders with apoptosis, and responders with entry in the cell cycle. Moreover, internal and direct interaction between leukemic BCR-HCDR3 epitopes at the plasma membrane and interaction between Bcl-2 and the IP3-receptor at the endoplasmic reticulum are also suspected to interfere with the intracellular Ca(2+) homeostasis in CLL-B cells. As a whole, the Ca(2+) pathway is emerging to play a key role in malignant CLL-B survival, disease progression, and last but not least, in the therapeutic response.

Allergic contact dermatitis (ACD) is induced by low-molecular weight electrophilic chemicals and metal ions. Chemical contact sensitizers trigger reactive oxygen species production and provoke electrophilic stress, leading to the accumulation of the transcription factor nuclear-related factor 2 (Nrf2) in innate immune cell types. The objective of this work was to identify the role of Nrf2 in the regulation of ACD. We used the local lymph node assay (LLNA) and the mouse ear swelling test (MEST) to study the role of Nrf2 in both the sensitization and elicitation phase in nrf2 knockout (nrf2(-/-)) and wild-type (nrf2(+/+)) mice. Five chemicals were used: two compounds known to react with cysteine residues, 2,4-dinitrochlorobenzene (DNCB) and cinnamaldehyde (CinA); one sensitizer known to exhibit mixed reactivity to cysteine and lysine residues, isophorone diisocyanate; and one reacting specifically with lysine residues, trimellitic anhydride and croton oil, a well-known irritant. In the MEST assay, DNCB (1 and 2%) induced a significant increase in ear thickness in nrf2(-/-) compared with nrf2(+/+) mice, suggesting a role for Nrf2 in the control of the inflammatory process. When DNCB was used at 0.25 and 0.5% or when mice were treated with CinA, inflammation was found only in nrf2(-/-) mice. In the LLNA, all chemical sensitizers induced an increase of lymphocyte proliferation in nrf2(-/-) compared with nrf2(+/+) mice for the same chemical concentration. These results reveal an important role for Nrf2 in controlling ACD and lymphocyte proliferation in response to sensitizers.

Immune suppressive activities exerted by regulatory T-cell subsets have several specific functions, including self-tolerance and regulation of adaptive immune reactions, and their dysfunction can lead to autoimmune diseases and contribute to AIDS and cancer. Two functionally distinct regulatory T-cell subsets are currently identified in peripheral tissues: thymus-developed natural T regulatory cells (nTregs) controlling self-tolerance and antiinflammatory IL-10-secreting type 1 regulatory T cells (Tr1) derived from Ag-stimulated T cells, which regulate inflammation-dependent adaptive immunity and minimize immunopathology. We establish herein that cell contact-mediated nTreg regulatory function is inhibited by inflammation, especially in the presence of the complement C3b receptor (CD46). Instead, as with other T-cell subsets, the latter inflammatory conditions of stimulation skew nTreg differentiation to Tr1 cells secreting IL-10, an effect potentiated by IFN-α. The clinical relevance of these findings was verified in a study of 152 lupus patients, in which we showed that lupus nTreg dysfunction is not due to intrinsic defects but is rather induced by C3b stimulation of CD46 and IFN-α and that these immune components of inflammation are directly associated with active lupus. These results provide a rationale for using anti-IFN-α Ab immunotherapy in lupus patients.

Melanoma is the most aggressive skin cancer in humans that often expresses MHC class II (MHC II) molecules, which could make these tumors eliminable by the immune system. However, this MHC II expression has been associated with poor prognosis, and there is a lack of immune-mediated eradication. The lymphocyte activation gene-3 (LAG-3) is a natural ligand for MHC II that is substantially expressed on melanoma-infiltrating T cells including those endowed with potent immune-suppressive activity. Based on our previous data showing the signaling capacity of MHC II in melanoma cells, we hypothesized that LAG-3 could contribute to melanoma survival through its MHC II signaling capacity in melanoma cells. In this study, we demonstrate that both soluble LAG-3 and LAG-3-transfected cells can protect MHC II-positive melanoma cells, but not MHC II-negative cells, from FAS-mediated and drug-induced apoptosis. Interaction of LAG-3 with MHC II expressed on melanoma cells upregulates both MAPK/Erk and PI3K/Akt pathways, albeit with different kinetics. Inhibition studies using specific inhibitors of both pathways provided evidence of their involvement in the LAG-3-induced protection from apoptosis. Altogether, our data suggest that the LAG-3-MHC II interaction could be viewed as a bidirectional immune escape pathway in melanoma, with direct consequences shared by both melanoma and immune cells. In the future, compounds that efficiently hinder LAG-3-MHC II interaction might be used as an adjuvant to current therapy for MHC II-positive melanoma.

Organ transplantation represents a unique therapeutic option for irreparable organ dysfunction and rejection of transplants results from a breakdown in operational tolerance. Although endothelial cells (ECs) are the first target in graft rejection following kidney transplantation, their capacity to alloactivate and generate particular T lymphocyte subsets that could intervene in this process remains unknown. By using an experimental model of microvascular endothelium, we demonstrate that, under inflammatory conditions, human ECs induced proliferation of memory CD4(+)CD45RA(-) T cells and selectively amplified proinflammatory Th17 and suppressive CD45RA(-)HLA-DR(+)FoxP3(bright) regulatory CD4(+) T lymphocytes (Tregs). Although HLA-DR expression on resting microvascular ECs was sufficient to induce proliferation of memory CD4(+) T cells, Treg amplification was dependent on the interaction with CD54, highly expressed only under inflammatory conditions. Moreover, expansion of Th17 cells was dependent on IL-6 and STAT-3, and inhibition of either specifically impaired Th17, without altering Treg expansion. Collectively these data reveal that the HLA-DR(+) ECs regulate the local inflammatory allogeneic response, promoting either an IL-6/STAT-3-dependent Th17 response or a contact-CD54-dependent regulatory response according to the cytokine environment. Finally, these data open therapeutic perspectives in human organ transplantation based on targeting the IL-6/STAT-3 pathway and/or promoting CD54 dependent Treg proliferation.