Surface CD52, CD84, and PTGER2 mark mature PMN-MDSCs from cancer patients and G-CSF-treated donors.

Precise molecular characterization of circulating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is hampered by their mixed composition of mature and immature cells and lack of specific markers. Here, we focus on mature CD66b+CD10+CD16+CD11b+ PMN-MDSCs (mPMN-MDSCs) from either cancer patients or healthy donors receiving G-CSF for stem cell mobilization (GDs). By RNA sequencing (RNA-seq) experiments, we report the identification of a distinct gene signature shared by the different mPMN-MDSC populations under investigation, also validated in mPMN-MDSCs from GDs and tumor-associated neutrophils (TANs) by single-cell RNA-seq (scRNA-seq) experiments. Analysis of such a gene signature uncovers a specific transcriptional program associated with mPMN-MDSC differentiation and allows us to identify that, in patients with either solid or hematologic tumors and in GDs, CD52, CD84, and prostaglandin E receptor 2 (PTGER2) represent potential mPMN-MDSC-associated markers. Altogether, our findings indicate that mature PMN-MDSCs distinctively undergo specific reprogramming during differentiation and lay the groundwork for selective immunomonitoring, and eventually targeting, of mature PMN-MDSCs.

Plasmacytoid Dendritic Cell, Slan+-Monocyte and Natural Killer Cell Counts Function as Blood Cell-Based Biomarkers for Predicting Responses to Immune Checkpoint Inhibitor Monotherapy in Non-Small Cell Lung Cancer Patients.

The advent of immune checkpoint inhibitors (ICIs), for instance, programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) blockers, has greatly improved the outcome of patients affected by non-small cell lung cancer (NSCLC). However, most NSCLC patients either do not respond to ICI monotherapy or develop resistance to it after an initial response. Therefore, the identification of biomarkers for predicting the response of patients to ICI monotherapy represents an urgent issue. Great efforts are currently dedicated toward identifying blood-based biomarkers to predict responses to ICI monotherapy. In this study, more commonly utilized blood-based biomarkers, such as the neutrophil-to-lymphocyte ratio (NLR) and the lung immune prognostic index (LIPI) score, as well as the frequency/number and activation status of various types of circulating innate immune cell populations, were evaluated in NSCLC patients at baseline before therapy initiation. The data indicated that, among all the parameters tested, low plasmacytoid dendritic cell (pDC), slan+-monocyte and natural killer cell counts, as well as a high LIPI score and elevated PD-L1 expression levels on type 1 conventional DCs (cDC1s), were independently correlated with a negative response to ICI therapy in NSCLC patients. The results from this study suggest that the evaluation of innate immune cell numbers and phenotypes may provide novel and promising predictive biomarkers for ICI monotherapy in NSCLC patients.

Immunological profile in a pediatric population of patients with spherocytosis. A single-center experience.

Spherocytosis is a hereditary disease caused by the deficiencies of different membrane proteins of red blood cells. Currently, splenectomy is the main therapeutic strategy available, although it is accompanied by an increased risk of sepsis. Several evidences have supported the hypothesis of spleen dysfunction in patients with spherocytosis that haven't yet undergone splenectomy. The aim of this study is to furtherly characterize this aspect, by describing the immune subpopulations in peripheral blood samples obtained from 41 pediatric patients with hereditary spherocytosis by flow cytometry, in order to evaluate changes in the composition of the immune populations compared to 16 healthy donors. Patients were divided in two groups: splenectomized and non-splenectomized. In the splenectomized population, data showed neutrophilic leukocytosis, thrombocytosis, increase in NK and reduction in CD4+ lymphocytes. However, we observed that most of the results obtained in the splenectomized group were found in the non-splenectomized patients as well (increase in neutrophils, in NK, reduction of CD19+, CD4+ lymphocytes and CD4+ and CD8+ naïve cells). The alterations of the immune system may be mainly due to the disease itself, regardless of splenectomy. Therefore, immunological criteria could be included in clinical phenotype assessment in order to better optimize the timing for splenectomy.

Inflammatory status in pediatric sickle cell disease: Unravelling the role of immune cell subsets.

Introduction: The mutation of the beta-globin gene that causes sickle cell disease (SCD) results in pleiotropic effects, such as hemolysis and vaso-occlusive crisis that can induce inflammatory mechanisms with deleterious consequences on the organism. Moreover, SCD patients display an increased susceptibility to infections. Few studies are currently available that evaluate a wide immunological profile in a pediatric population. This study proposes an evaluation of the immune profile in subjects with SCD in a pediatric population through a detailed analysis by flow cytometry. Methods and Materials: Peripheral blood samples from 53 pediatric patients with SCD (mean age 9.8 years, interquartile range 9 years) were obtained and then analyzed by flow cytometry, in order to evaluate changes in the immune populations compared to 40 healthy donors (mean age 7.3 years, interquartile range 9.5 years). Results: Our data showed an increase in neutrophils (with a reduction in the CD62L + subpopulation) and monocytes (with a decrease in HLA-DRlow monocytes) with normal values of lymphocytes in SCD patients. In the lymphocyte subpopulations analysis we observed lower values of CD4+ T cells (with higher number of memory and central memory T lymphocytes) with increased frequency of CD8+ T cells (with a predominant naive pattern). Moreover, we observed higher values of CD39+ Tregs and lower HLA-DR+ and CD39- T cells with an increased Th17, Th1-17 and Th2 response. Conclusion: We observed immunological alterations typical of an inflammatory status (increase in activated neutrophils and monocytes) associated with a peculiar Treg pattern (probably linked to a body attempt to minimize inflammation intrinsic to SCD). Furthermore, we highlighted a T helper pathway associated with inflammation in line with other studies. Our data showed that immunological markers may have an important role in the understanding the pathophysiology of SCD and in optimizing targeted therapeutic strategies for each patient.

Tumor-associated neutrophils (TANs) in human carcinoma-draining lymph nodes: a novel TAN compartment.

OBJECTIVES: The role of tumor-associated neutrophils (TANs) in the nodal spread of cancer cells remains unexplored. The present study evaluates the occurrence and clinical significance of human nodal TANs. METHODS: The relevance, derivation, phenotype and interactions of nodal TANs were explored via a large immunohistochemical analysis of carcinoma-draining lymph nodes, and their clinical significance was evaluated on a retrospective cohort of oral squamous cell carcinomas (OSCC). The tumor-promoting function of nodal TAN was probed in the OSCC TCGA dataset combining TAN and epithelial-to-mesenchymal transition (EMT) signatures. RESULTS: The pan-carcinoma screening identified a consistent infiltration (59%) of CD66b+  TANs in tumor-draining lymph nodes (TDLNs). Microscopic findings, including the occurrence of intra-lymphatic conjugates of TANs and cancer cells, indicate that TANs migrate through lymphatic vessels. In vitro experiments revealed that OSCC cell lines sustain neutrophil viability and activation via release of GM-CSF. Moreover, by retrospective analysis, a high CD66b+ TAN density in M-TDLNs of OSCC (n = 182 patients) predicted a worse prognosis. The analysis of the OSCC-TCGA dataset unveiled that the expression of a set of neutrophil-specific genes in the primary tumor (PT) is highly associated with an EMT signature, which predicts nodal spread. Accordingly, in the PT of OSCC cases, CD66b+TANs co-localised with PDPN+S100A9- EMT-switched tumor cells in areas of lymphangiogenesis. The pro-EMT signature is lacking in peripheral blood neutrophils from OSCC patients, suggesting tissue skewing of TANs. CONCLUSION: Our findings are consistent with a novel pro-tumoral TAN compartment that may promote nodal spread via EMT, through the lymphatics.

Deciphering myeloid-derived suppressor cells: isolation and markers in humans, mice and non-human primates.

In cancer, infection and inflammation, the immune system's function can be dysregulated. Instead of fighting disease, immune cells may increase pathology and suppress host-protective immune responses. Myeloid cells show high plasticity and adapt to changing conditions and pathological challenges. Despite their relevance in disease pathophysiology, the identity, heterogeneity and biology of myeloid cells is still poorly understood. We will focus on phenotypical and functional markers of one of the key myeloid regulatory subtypes, the myeloid derived suppressor cells (MDSC), in humans, mice and non-human primates. Technical issues regarding the isolation of the cells from tissues and blood, timing and sample handling of MDSC will be detailed. Localization of MDSC in a tissue context is of crucial importance and immunohistochemistry approaches for this purpose are discussed. A minimal antibody panel for MDSC research is provided as part of the Mye-EUNITER COST action. Strategies for the identification of additional markers applying state of the art technologies such as mass cytometry will be highlighted. Such marker sets can be used to study MDSC phenotypes across tissues, diseases as well as species and will be crucial to accelerate MDSC research in health and disease.

Role of MyD88 signaling in the imiquimod-induced mouse model of psoriasis: focus on innate myeloid cells.

Psoriasis is a chronic skin disease associated with deregulated activation of immune cells and keratinocytes. In this study, we used the imiquimod (IMQ)-induced mouse model of psoriasis to dissect better the contribution of hematopoietic and skin-resident stromal cells to psoriasis development. The comparison of disease development in mice carrying the hematopoietic cell-specific deletion of MyD88 (Myd88fl/flVav-cre+ mice) with mice carrying the total MyD88 deficiency (Myd88-/- mice), we show that the progression of skin and systemic inflammation, as well as of epidermal thickening, was completely dependent on MyD88 expression in hematopoietic cells. However, both Myd88-/- mouse strains developed some degree of epidermal thickening during the initial stages of IMQ-induced psoriasis, even in the absence of hematopoietic cell activation and infiltration into the skin, suggesting a contribution of MyD88-independent mechanisms in skin-resident stromal cells. With the use of conditional knockout mouse strains lacking MyD88 in distinct lineages of myeloid cells (Myd88fl/flLysM-cre+ and Myd88fl/flMRP8-cre+ mice), we report that MyD88 signaling in monocytes and Mϕ, but not in neutrophils, plays an important role in disease propagation and exacerbation by modulating their ability to sustain γδ T cell effector functions via IL-1ß and IL-23 production. Overall, these findings add new insights into the specific contribution of skin-resident stromal vs. hematopoietic cells to disease initiation and progression in the IMQ-induced mouse model of psoriasis and uncover a potential novel pathogenic role for monocytes/Mϕ to psoriasis development.

Mature CD10+ and immature CD10- neutrophils present in G-CSF-treated donors display opposite effects on T cells.

The identification of discrete neutrophil populations, as well as the characterization of their immunoregulatory properties, is an emerging topic under extensive investigation. In such regard, the presence of circulating CD66b+ neutrophil populations, exerting either immunosuppressive or proinflammatory functions, has been described in several acute and chronic inflammatory conditions. However, due to the lack of specific markers, the precise phenotype and maturation status of these neutrophil populations remain unclear. Herein, we report that CD10, also known as common acute lymphoblastic leukemia antigen, neutral endopeptidase, or enkephalinase, can be used as a marker that, within heterogeneous populations of circulating CD66b+ neutrophils present in inflammatory conditions, clearly distinguishes the mature from the immature ones. Accordingly, we observed that the previously described immunosuppressive neutrophil population that appears in the circulation of granulocyte colony-stimulating factor (G-CSF)-treated donors (GDs) consists of mature CD66b+CD10+ neutrophils displaying an activated phenotype. These neutrophils inhibit proliferation and interferon γ (IFNγ) production by T cells via a CD18-mediated contact-dependent arginase 1 release. By contrast, we found that immature CD66b+CD10- neutrophils, also present in GDs, display an immature morphology, promote T-cell survival, and enhance proliferation and IFNγ production by T cells. Altogether, our findings uncover that in GDs, circulating mature and immature neutrophils, distinguished by their differential CD10 expression, exert opposite immunoregulatory properties. Therefore, CD10 might be used as a phenotypic marker discriminating mature neutrophils from immature neutrophil populations present in patients with acute or chronic inflammatory conditions, as well as facilitating their isolation, to better define their specific immunoregulatory properties.

Human neutrophils in the saga of cellular heterogeneity: insights and open questions.

Recent findings have uncovered novel fascinating aspects of the biology of neutrophils, which ultimately attribute to these cells a broader role in inflammation and immunity. One aspect that is currently under intensive investigation is the notion of neutrophil 'heterogeneity'. Studies examining neutrophils in a variety of acute and chronic inflammatory conditions report, in fact, the recovery of CD66b(+) cells displaying neutrophil-like morphology at different degrees of maturation/activation, able to exert either immunosuppressive or proinflammatory properties. These heterogeneous populations of mature and immature neutrophils are indicated with a variety of names, including 'low density neutrophils (LDNs)', 'low density granulocytes (LDGs)', 'granulocytic-myeloid derived suppressor cells (G-MDSCs)', and immunosuppressive neutrophils. However, due to the lack of discrete markers that can unequivocally allow their specific identification and isolation, the precise phenotype and function of all these presumably novel, neutrophil-like, populations have not been correctly defined yet. Aim of this article is to summarize current knowledge on the mature and immature neutrophil populations described to date, featuring immunosuppressive or proinflammatory properties, often defined as 'subsets', as well as to critically discuss unresolved issues in the field.

Identification of granulocytic myeloid-derived suppressor cells (G-MDSCs) in the peripheral blood of Hodgkin and non-Hodgkin lymphoma patients.

Human granulocytic myeloid-derived suppressor cells (G-MDSCs) have been described as low-density immunosuppressive CD66b+CD33dimHLA-DR-granulocytes that co-purify with mononuclear cells after density gradient centrifugation of blood from cancer patients. The role of G-MDSCs in Hodgkin (HL) and non-Hodgkin lymphoma (NHL) remains unclear.The percentage and immunophenotype of CD66b+CD33dimHLA-DR-cells were analyzed in PBMCs from HL and B-cell NHL patients (n = 124) and healthy donors (n = 48). The immunosuppressive functions of these cells were tested in vitro. Correlations between CD66b+CD33dimHLA-DR-cells and patient clinicopathological features and outcome, were evaluated.CD66b+CD33dimHLA-DR-cells were increased in PBMCs from HL and B-cell NHL patients as compared to healthy donors: 2.18 (0.02-70.92) vs 0.42 (0.04-2.97), p < 0.0001. Their percentage remained significantly higher even considering HL (n = 31), indolent (n = 31) and aggressive (n = 62) B-cell NHL patients separately: 1.54 (0.28-26.34), 2.15 (0.02-20.08), and 2.96 (0.25-70.92), respectively, p < 0.0001. CD66b+CD33dimHLA-DR-cells in patient PBMCs were mostly composed of mature CD11b+CD16+ low-density neutrophils in an activated status, as revealed by their higher CD11b and CD66b expression as compared to conventionally isolated (normal-density) autologous or healthy donor neutrophils. The in vitro depletion of CD66b+ cells from patient PBMCs restored the proliferation of autologous T cells. Higher frequencies of CD66b+CD33dimHLA-DR- G-MDSCs correlated significantly with unfavorable prognostic index scores and a shorter freedom from disease progression.PBMCs from HL and B-cell NHL patients contain a population of CD66b+CD33dimHLA-DR- G-MDSCs, mostly composed of activated low-density neutrophils with immunosuppressive properties. These findings disclose a previously unknown G-MDSC-mediated mechanism of immune-escape in lymphomas, therefore anticipating possible targets for therapeutic interventions.