Characterization of a novel mouse model with genetic deletion of CD177

Regulatory role of CD177+ neutrophils in BMP signaling pathway and its implications for inflammatory bowel disease, sepsis, and intestinal tumors

OBJECTIVES

Inflammatory bowel disease (IBD), sepsis, and intestinal tumors are major health threats. This study aimed to explore the regulatory role of CD177+ neutrophils in the BMP signaling pathway and its impact on the onset, progression, and treatment of these diseases.

METHODS

Gene expression data from the Gene Expression Omnibus (GEO) database for IBD and sepsis were retrieved. Bioinformatics methods like background correction, normalization, and differential expression analysis were used. Weighted gene co-expression network analysis (WGCNA), gene functional enrichment analysis, pan-cancer analysis, single-cell analysis, and in vitro experiments including Caco-2 cell culture, cell proliferation assay (CCK-8), flow cytometry apoptosis analysis, quantitative real-time PCR (qRT-PCR), and plate colony formation assay were performed.

RESULTS

Key genes associated with IBD and sepsis, such as BMP2, BMP4, BMP6, BMP8A, and CD177, were identified. WGCNA in sepsis found two significant modules related to key clinical outcomes. Core gene screening revealed seven shared genes between IBD and sepsis, and enrichment analysis showed involvement in important biological processes and pathways. Pan-cancer analysis showed diverse gene expression patterns and correlations with immune dynamics. Single-cell transcriptomics provided insights into the tumor microenvironment. In vitro experiments demonstrated that CD177 knockdown affected BMP signaling pathway-related gene expression, ROS production, apoptosis, and cell proliferation.

CONCLUSION

CD177+ neutrophils play a crucial role in regulating the BMP signaling pathway in IBD, sepsis, and intestinal tumors. These findings offer potential therapeutic targets, but further clinical validation is required to translate them into effective treatment strategies.

Distinct immunophenotypic profiles and neutrophil heterogeneity in colorectal cancer

Colorectal cancer (CRC) exhibits significant molecular and immunological heterogeneity. Neutrophil infiltration patterns play a crucial yet poorly understood role in tumor progression and patient outcomes. This study presents a comprehensive single-cell atlas of the CRC tumor microenvironment (TME), integrating transcriptomic data from 388,511 cells across 98 samples from 63 patients. Employing advanced computational methods, we stratified patients based on their immune cell infiltration profiles, revealing distinct immunophenotypes with potential therapeutic implications. Our analysis focused on tissue-resident neutrophils (TRNs) and uncovered previously uncharacterized subpopulations with diverse functional states. Trajectory inference analysis revealed a dynamic differentiation path from normal-associated neutrophils to tumor-associated neutrophils, highlighting the remarkable plasticity of these cells within the tumor environment. By integrating single-cell data with bulk transcriptomic and clinical information, we identified specific neutrophil-derived gene signatures associated with poor prognosis in CRC, suggesting their potential as novel prognostic biomarkers. This study not only provides unprecedented insights into neutrophil heterogeneity in CRC but also identifies potential targets for immunomodulatory therapies. Our findings lay the groundwork for developing more nuanced, personalized immunotherapeutic strategies for CRC, potentially improving treatment efficacy for patients who currently show a limited response to existing immunotherapies.

Aberrant expansion of CD177+ neutrophils promotes endothelial dysfunction in systemic lupus erythematosus via neutrophil extracellular traps

OBJECTIVE

Aberrant neutrophil activation is implicated in the pathogenesis of systemic lupus erythematosus (SLE) and its related comorbidities. We found that CD177 was one of the most highly up-regulated genes at the transcriptional level in purified neutrophils from SLE patients. In this study, we aimed to explore the role of CD177+ neutrophils in the pathogenesis of SLE.

METHODS

Expression of CD177 was analyzed by neutrophil transcriptome and flow cytometry. CD177+ neutrophils and CD177-neutrophils were isolated to determine the role of neutrophils-derived NETs in endothelium dysfunction. Wild type and CD177-/- murine model of lupus were analyzed for organ involvement, endothelium-dependent vasorelaxation, serum autoantibodies, and innate and adaptive immune responses in an imiquimod (IMQ)-induced lupus model.

RESULTS

CD177MFI-hi neutrophils and CD177MFI-hi low-density granulocytes (LDGs) were expanded in active SLE, which were weakly but significantly associated with disease activity. CD177+neutrophils displayed enhanced production of reactive oxygen species (ROS) and NETs, which impaired the murine aortic endothelium-dependent vasorelaxation and induced endothelial cell apoptosis. Moreover, CD177-/- mice exposed to IMQ showed alleviated splenomegaly, endothelium-dependent vasorelaxation, and renal immune complex deposition.

CONCLUSIONS

Our findings indicated that CD177 MFI-hi may serve as a novel biomarker for monitoring disease activity in SLE. Further, CD177+ neutrophils may play a vasculopathic role in cardiovascular disease (CVD) via NETs formation, suggesting that specific targeting CD177+ neutrophil subset may have therapeutic effect in SLE but reducing the levels of NETs-prone neutrophils.

Comprehensive analysis of myeloid reporter mice

Macrophages are a pivotal cell type within the synovial lining and sub-lining of the joint, playing a crucial role in maintaining homeostasis of synovium. Although fate-mapping techniques have been employed to differentiate synovial macrophages from other synovial myeloid cells, no comprehensive study has yet been conducted within the mouse synovial macrophage compartment. In this study, we present, for the first time, lineage tracing results from 18 myeloid-specific fate-mapping models in mouse peripheral blood (PB) and synovial tissue. The identification of synovial macrophages and monocyte-lineage cells through flow cytometry was further validated using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) datasets. These findings provide a valuable methodological tool for researchers to select appropriate models for studying the function of synovial myeloid cells and serve as a reference for investigations in other tissue types.

CD177, MYBL2, and RRM2 Are Potential Biomarkers for Musculoskeletal Infections

BACKGROUND

Biomarkers of infection are measurable indicators that reflect the presence of an infection in the body. They are particularly valuable for detecting infections and tracking treatment responses. Previous transcriptome analysis of peripheral blood mononuclear cells (PBMCs) collected from patients during the active phase of diabetic foot infection identified the upregulation of several genes, including a neutrophil-specific cell surface glycoprotein, CD177, an Myb-related transcription factor 2 (MYBL2), and ribonucleotide reductase regulatory subunit M2 (RRM2). We aimed to investigate whether these observations in diabetic foot infections could be extrapolated to other musculoskeletal infections.

QUESTIONS/PURPOSES

(1) Are the protein concentrations of CD177, MYBL2, and RRM2 elevated in serum or PBMCs of patients with musculoskeletal infections? (2) Do serum and PBMC concentrations of CD177, MYBL2, and RRM2 decrease in response to antibiotic therapy? (3) Can these biomarkers give diagnostic accuracy and differentiate patients with musculoskeletal infections from controls?

METHODS

From April 2023 to June 2024, we treated 26 patients presenting with clinical symptoms and signs of acute musculoskeletal infections, including elevated inflammatory markers (white blood cell [WBC] and C-reactive protein [CRP]) and local changes such as swelling, erythema, tenderness or pain, warmth, purulent drainage, sinus tract, or wound leading to bone or hardware. Diagnosis included periprosthetic joint infection (PJI), foot and ankle infection (FAI), fracture-related infection (FRI), and septic arthritis of the native joints. Patients with chronic recurrent osteomyelitis, PJI, or FRI were excluded from the study. Among the 26 patients deemed potentially eligible, 19% (5) were excluded for the following reasons: prison inmate (1), unable to provide consent because of severe sepsis (1), mental illness (1), and declined to participate (2). Of the 81% (21) of patients who provided consent, cultures from 9.5% (2) were negative. These two patients were ultimately diagnosed with inflammatory arthritis: gout (1) and rheumatoid arthritis (1); thus, the musculoskeletal infection group for analysis consisted of 73.1% (19 of 26) of patients. A control group of 21 patients undergoing elective foot or ankle deformity correction surgery without infections or systemic inflammation was included. Because foot or ankle deformity is highly unlikely to influence the immunologic profile of the subjects, we believed that these patients would serve as an appropriate control group. Other than the absence of infection and the lower prevalence of diabetes mellitus, the control group was comparable to the study group in terms of demographics and clinical factors, including age and sex distribution. We collected blood samples from both patients and controls and quantified CD177, MYBL2, and RRM2 RNA transcription levels in the PBMC using qRT-PCR. We also assessed protein concentrations in the serum and PBMC using an enzyme-linked immunosorbent assay. A comparative analysis of the three biomarkers was performed on 19 patients with musculoskeletal infections with positive cultures and 21 controls to assess their diagnostic potential using the unpaired nonparametric t-test with the Mann-Whitney test. We obtained 8-week follow-up blood samples from seven patients with musculoskeletal infections who clinically healed. Healing was defined by normalization of inflammatory markers (WBC and CRP) and absence of swelling, erythema, local tenderness or pain, warmth, purulent drainage, sinus tract, or open wound. We performed a comparative analysis of the seven patients during active infection and after treatment to determine a change in the level of CD177, MYBL2, and RRM2 in their serum and PBMCs. These findings were also compared with those of the control group. We evaluated the diagnostic accuracy of CD177, MYBL2, and RRM2 for musculoskeletal infections using receiver operating characteristic (ROC) curve analysis.

RESULTS

The musculoskeletal infections group showed a larger increased serum and PBMC concentrations of CD177, MYBL2, and RRM2 proteins compared with the control group. The mean protein concentrations of CD177, MYBL2, and RRM2 were increased in the serum and PBMC of the musculoskeletal infections group compared with the controls. Serum levels of all biomarkers investigated were higher in musculoskeletal infections group compared with the control group (CD177 227 [155 to 432] versus 54 [10 to 100], difference of medians 173, p < 0.01; MYBL2 255 [231 to 314] versus 180 [148 to 214], difference of medians 75, p < 0.01; RRM2 250 [216 to 305] versus 190 [148 to 255], difference of medians 60, p < 0.01). Similarly, PBMC levels of all biomarkers were higher in the musculoskeletal infections group (CD177 55.3 [39.1 to 80.5] versus 17.5 [10.5 to 27.5], difference of medians 37.8, p < 0.01; MYBL2 144 [114 to 190] versus 91 [70 to 105], difference of medians 53, p < 0.01; RRM2 168 [143 to 202] versus 100 [77.5 to 133], difference of medians 68, p < 0.01). Additionally, serum levels of all biomarkers decreased in seven patients with musculoskeletal infections after infection treatment (CD177 3080 [2690 to 3320] versus 4250 [3100 to 8640], difference of medians 1170, p < 0.01; MYBL2 4340 [4120 to 4750] versus 5010 [4460 to 5880], difference of medians 670, p < 0.01; RRM2 4350 [3980 to 5000] versus 5025 [4430 to 6280], difference of medians 675, p = 0.01). Similarly, PBMC levels of all biomarkers were lower after infection treatment (CD177 805 [680 to 980] versus 1025 [750 to 1610], difference of medians 220, p < 0.01; MYBL2 2300 [2100 to 2550] versus 2680 [2220 to 3400], difference of medians 380, p = 0.02; RRM2 2720 [2500 to 3200] versus 3350 [2825 to 4030], difference of medians 630, p < 0.01). The area under the ROC curve for diagnosing musculoskeletal infections in the serum and PBMC was as follows: CD177 95% confidence interval [CI] > 0.99 and > 0.99, MYBL2 95% CI > 0.99 and > 0.99, and RRM2 95% CI = 0.96 and > 0.99, respectively.

CONCLUSION

We may utilize blood-based tests for CD177, MYBL2, and RRM2 to aid in the diagnosis of musculoskeletal infections, particularly when arthrocentesis or obtaining tissue culture is challenging. They may also assist in monitoring treatment response. As some of these biomarkers may also be elevated in other inflammatory conditions, a large-scale clinical study is needed to confirm their reliability in differentiating musculoskeletal infections from other inflammatory conditions.

CLINICAL RELEVANCE

CD177, MYBL2, and RRM2 proteins in blood samples may serve as novel biomarkers for diagnosing and monitoring treatment response in musculoskeletal infections.

Meningeal neutrophil immune signaling influences behavioral adaptation following threat

Social creatures must attend to threat signals from conspecifics and respond appropriately, both behaviorally and physiologically. In this work, we show in mice a threat-sensitive immune mechanism that orchestrates psychological processes and is amenable to social modulation. Repeated encounters with socially cued threats triggered meningeal neutrophil (MN) priming preferentially in males. MN activity was correlated with attenuated defensive responses to cues. Canonical neutrophil-specific activation marker CD177 was upregulated after social threat cueing, and its genetic ablation abrogated male behavioral phenotypes. CD177 signals favored meningeal T helper (Th)1-like immune bias, which blunted neural response to threatening stimuli by enhancing intrinsic GABAergic inhibition within the prelimbic cortex via interferon-gamma (IFN-γ). MN signaling was sensitized by negative emotional states and governed by socially dependent androgen release. This male-biased hormone/neutrophil regulatory axis is seemingly conserved in humans. Our findings provide insights into how immune responses influence behavioral threat responses, suggesting a possible neuroimmune basis of emotional regulation.

Unveiling shared diagnostic biomarkers and molecular mechanisms between T2DM and sepsis: Insights from bioinformatics to experimental assays

Septic patients with T2DM were prone to prolonged recovery and unfavorable prognoses. Thus, this study aimed to pinpoint potential genes related to sepsis with T2DM and develop a predictive model for the disease. The candidate genes were screened using protein-protein interaction networks (PPI) and machine learning algorithms. The nomogram and receiver operating characteristic curve were developed to assess the diagnostic efficiency of the biomarkers. The relationship between sepsis and immune cells was analyzed using the CIBERSORT algorithm. The biomarkers were validated by qPCR and western blotting in basic experiments, and differences in organ damage in mice were studied. Three genes (MMP8, CD177, and S100A12) were identified using PPI and machine learning algorithms, demonstrating strong predictive capabilities. These biomarkers presented significant differences in gene expression patterns between diseased and healthy conditions. Additionally, the expression levels of biomarkers in mouse models and blood samples were consistent with the findings of the bioinformatics analysis. The study elucidated the common molecular mechanisms associated with the pathogenesis of T2DM and sepsis and developed a gene signature-based prediction model for sepsis. These findings provide new targets for the diagnosis and intervention of sepsis complicated with T2DM.

Dual role of CD177 + neutrophils in inflammatory bowel disease: a review

Inflammatory bowel disease (IBD) represents a group of recurrent chronic inflammatory disorders associated with autoimmune dysregulation, typically characterized by neutrophil infiltration and mucosal inflammatory lesions. Neutrophils, as the earliest immune cells to arrive at inflamed tissues, play a dual role in the onset and progression of mucosal inflammation in IBD. Most of these cells specifically express CD177, a molecule increasingly recognized for its critical role in the pathogenesis of IBD. Under IBD-related inflammatory stimuli, CD177 is highly expressed on neutrophils and promotes their migration. CD177 + neutrophils activate bactericidal and barrier-protective functions at IBD mucosal inflammation sites and regulate the release of inflammatory mediators highly correlated with the severity of inflammation in IBD patients, thus playing a dual role. However, mitigating the detrimental effects of neutrophils in inflammatory bowel disease remains a challenge. Based on these data, we have summarized recent articles on the role of neutrophils in intestinal inflammation, with a particular emphasis on CD177, which mediates the recruitment, transepithelial migration, and activation of neutrophils, as well as their functional consequences. A better understanding of CD177 + neutrophils may contribute to the development of novel therapeutic targets to selectively modulate the protective role of this class of cells in IBD.

Investigation of pulmonary inflammatory responses following intratracheal instillation of and inhalation exposure to polypropylene microplastics

BACKGROUND

Microplastics have been detected in the atmosphere as well as in the ocean, and there is concern about their biological effects in the lungs. We conducted a short-term inhalation exposure and intratracheal instillation using rats to evaluate lung disorders related to microplastics. We conducted an inhalation exposure of polypropylene fine powder at a low concentration of 2 mg/m3 and a high concentration of 10 mg/m3 on 8-week-old male Fischer 344 rats for 6 h a day, 5 days a week for 4 weeks. We also conducted an intratracheal instillation of polypropylene at a low dose of 0.2 mg/rat and a high dose of 1.0 mg/rat on 12-week-old male Fischer 344 rats. Rats were dissected from 3 days to 6 months after both exposures, and bronchoalveolar lavage fluid (BALF) and lung tissue were collected to analyze lung inflammation and lung injury.

RESULTS

Both exposures to polypropylene induced a persistent influx of inflammatory cells and expression of CINC-1, CINC-2, and MPO in BALF from 1 month after exposure. Genetic analysis showed a significant increase in inflammation-related factors for up to 6 months. The low concentration in the inhalation exposure of polypropylene also induced mild lung inflammation.

CONCLUSION

These findings suggest that inhaled polypropylene, which is a microplastic, induces persistent lung inflammation and has the potential for lung disorder. Exposure to 2 mg/m3 induced inflammatory changes and was thought to be the Lowest Observed Adverse Effect Level (LOAEL) for acute effects of polypropylene. However, considering the concentration of microplastics in a real general environment, the risk of environmental hazards to humans may be low.

CD177 on neutrophils engages stress-related behavioral changes in male mice

Persistent psychological stress can affect immune homeostasis and is a key factor in the development of depression. Many efforts are focused on the identifcation of pathways that link the immune system and mood disorders. Here, we found that psychological stress caused an increase in the frequency of brain-associated neutrophils and the level of neutrophil-specific antigen CD177 on peripheral neutrophils in male mice. Upregulated levels of blood CD177 are associated with depression in humans. Neutrophil depletion or Cd177 deficiency protected mice from stress-induced behavioral deficits. Importantly, adoptive transfer of CD177+ neutrophils from stressed mice increased the frequency of brain-associated leukocytes, including neutrophils, and caused behavioral defects in naive mice. These effects may be related to the endothelial adhesion advantage of CD177+ neutrophils and the interference of serine protease on endothelial junction. Our findings suggest a critical link between circulating CD177+ neutrophils and psychological stress-driven behavioral disorder.

CD177 is a novel IgG Fc receptor and CD177 genetic variants affect IgG-mediated function

CD177 plays an important role in the proliferation and differentiation of myeloid lineage cells including neutrophils, myelocytes, promyelocytes, megakaryocytes, and early erythroblasts in bone marrow. CD177 deficiency is a common phenotype in humans. Our previous studies revealed genetic mechanisms of human CD177 deficiency and expression variations. Up to now, immune functions of CD177 remain undefined. In the current study, we revealed human IgG as a ligand for CD177 by using flow cytometry, bead-rosette formation, and surface plasmon resonance (SPR) assays. In addition, we show that CD177 variants affect the binding capacity of CD177 for human IgG. Furthermore, we show that the CD177 genetic variants significantly affect antibody-dependent cell-mediated cytotoxicity (ADCC) function. The demonstration of CD177 as a functional IgG Fc-receptor may provide new insights into CD177 immune function and genetic mechanism underlying CD177 as biomarkers for human diseases.

Classical monocyte ontogeny dictates their functions and fates as tissue macrophages

Classical monocytes (CMs) are ephemeral myeloid immune cells that circulate in the blood. Emerging evidence suggests that CMs can have distinct ontogeny and originate from either granulocyte-monocyte- or monocyte-dendritic-cell progenitors (GMPs or MDPs). Here, we report surface markers that allowed segregation of murine GMP- and MDP-derived CMs, i.e., GMP-Mo and MDP-Mo, as well as their functional characterization, including fate definition following adoptive cell transfer. GMP-Mo and MDP-Mo yielded an equal increase in homeostatic CM progeny, such as blood-resident non-classical monocytes and gut macrophages; however, these cells differentially seeded various other selected tissues, including the dura mater and lung. Specifically, GMP-Mo and MDP-Mo differentiated into distinct interstitial lung macrophages, linking CM dichotomy to previously reported pulmonary macrophage heterogeneity. Collectively, we provide evidence for the existence of two functionally distinct CM subsets in the mouse that differentially contribute to peripheral tissue macrophage populations in homeostasis and following challenge.

Peripheral priming induces plastic transcriptomic and proteomic responses in circulating neutrophils required for pathogen containment

Neutrophils rapidly respond to inflammation and infection, but to which degree their functional trajectories after mobilization from the bone marrow are shaped within the circulation remains vague. Experimental limitations have so far hampered neutrophil research in human disease. Here, using innovative fixation and single-cell-based toolsets, we profile human and murine neutrophil transcriptomes and proteomes during steady state and bacterial infection. We find that peripheral priming of circulating neutrophils leads to dynamic shifts dominated by conserved up-regulation of antimicrobial genes across neutrophil substates, facilitating pathogen containment. We show the TLR4/NF-κB signaling-dependent up-regulation of canonical neutrophil activation markers like CD177/NB-1 during acute inflammation, resulting in functional shifts in vivo. Blocking de novo RNA synthesis in circulating neutrophils abrogates these plastic shifts and prevents the adaptation of antibacterial neutrophil programs by up-regulation of distinct effector molecules upon infection. These data underline transcriptional plasticity as a relevant mechanism of functional neutrophil reprogramming during acute infection to foster bacterial containment within the circulation.

CD177 is a novel IgG Fc receptor and CD177 genetic variants affect IgG-mediated function

CD177 plays an important role in the proliferation and differentiation of myeloid lineage cells including neutrophils, myelocytes, promyelocytes, megakaryocytes, and early erythroblasts in bone marrow. CD177 deficiency is a common phenotype in humans. Our previous studies revealed genetic mechanisms of human CD177 deficiency and expression variations. Up to now, immune functions of CD177 remain undefined. In the current study, we revealed human IgG as a ligand for CD177 by using flow cytometry, bead-rosette formation, and surface plasmon resonance (SPR) assays. In addition, we show that CD177 variants affect the binding capacity of CD177 for human IgG. Furthermore, we showed that the CD177 genetic variants significantly affect antibody-dependent cell-mediated cytotoxicity (ADCC) function. The demonstration of CD177 as a functional IgG Fc-receptor may provide new insights into CD177 immune function and genetic mechanism underlying CD177 as biomarkers for human diseases.

Clinical exome sequencing findings in 1589 patients

Clinical exome sequencing (CES) is important for the diagnosis of Mendelian diseases, which are clinically and etiologically heterogeneous. Sharing of large amounts of CES data associated with clinical findings will increase the accuracy of variant interpretation. We performed a retrospective study to state the diagnostic yield of CES in 1589 patients with a wide phenotypic spectrum. CES was performed using the Sophia Clinical Exome Sequencing Kit with 4493 genes, followed by sequencing on a NextSeq 500 system. The diagnosis rate was 36.8% when only pathogenic and likely pathogenic variants were included. Consanguineous unions and positive family history were associated with a high diagnostic yield. The neurological disease group had the highest number of patients. The groups with high diagnosis rates were ear, eye, and muscle disease groups. Seven candidate genes (EFHC2, HSPB3, FAAH2, ITGB1, GYG2, CD177, and CSTF2T) that are not yet associated with human diseases were identified. Owing to the high diagnostic yield of CES compared with that of other genetic tests, it can be used as a standard diagnostic test in patients with rare genetic disorders that require a wide differential diagnosis, especially in laboratories with limited resources.

Immune cell targeting nanoparticles: a review

Immune cells are attractive targets for therapy as they are direct participants in a variety of diseases. Delivering a therapeutic agent only to cells that act on a disease by distinguishing them from other cells has the advantage of concentrating the therapeutic effect and lowering systemic side effects. Distinguishing each immune cell from other immune cells to deliver substances, including drugs and genes, can be achieved using nanotechnology. And also nanoparticles can ensure in vivo stability and sustained drug release. In addition, there is an ease of surface modification, which is an important characteristic that can be utilized in targeted drug delivery systems. This characteristic allows us to utilize various properties that are specifically expressed in each immune cell. A number of studies have delivered various substances specifically to immune cells through surface engineering with active target ligands that can target each immune cell and enzyme-responsive coating, and demonstrated high therapeutic effects compared to conventional treatments. Progress in research on target delivery has been suggested to be a breakthrough for the treatments of various diseases, including cancer treatment.

CD177 modulates the function and homeostasis of tumor-infiltrating regulatory T cells

Regulatory T (Treg) cells are one of the major immunosuppressive cell types in cancer and a potential target for immunotherapy, but targeting tumor-infiltrating (TI) Treg cells has been challenging. Here, using single-cell RNA sequencing of immune cells from renal clear cell carcinoma (ccRCC) patients, we identify two distinct transcriptional fates for TI Treg cells, Fate-1 and Fate-2. The Fate-1 signature is associated with a poorer prognosis in ccRCC and several other solid cancers. CD177, a cell surface protein normally expressed on neutrophil, is specifically expressed on Fate-1 TI Treg cells in several solid cancer types, but not on other TI or peripheral Treg cells. Mechanistically, blocking CD177 reduces the suppressive activity of Treg cells in vitro, while Treg-specific deletion of Cd177 leads to decreased tumor growth and reduced TI Treg frequency in mice. Our results thus uncover a functional CD177+ TI Treg population that may serve as a target for TI Treg-specific immunotherapy.

Tumor Temporal Proteome Profiling Reveals the Immunological Triple Offensive Induced by Synthetic Anti-Cancer Salmonella

The engineered “obligate” anaerobic Salmonella typhimurium strain YB1 shows a prominent ability to repress tumor growth and metastasis, which has great potential as a novel cancer immunotherapy. However, the antitumor mechanism of YB1 remains unelucidated. To resolve the proteome dynamics induced by the engineered bacteria, we applied tumor temporal proteome profiling on murine bladder tumors after intravenous injection of either YB1 or PBS as a negative control. Our data suggests that during the two weeks treatment of YB1 injections, the cured tumors experienced three distinct phases of the immune response. Two days after injection, the innate immune response was activated, particularly the complement and blood coagulation pathways. In the meantime, the phagocytosis was initiated. The professional phagocytes such as macrophages and neutrophils were recruited, especially the infiltration of iNOS⁺ and CD68⁺ cells was enhanced. Seven days after injection, substantial amount of T cells was observed at the invasion margin of the tumor. As a result, the tumor shrunk significantly. Overall, the temporal proteome profiling can systematically reveal the YB1 induced immune responses in tumor, showing great promise for elucidating the mechanism of bacteria-mediated cancer immunotherapy.

Ly6G deficiency alters the dynamics of neutrophil recruitment and pathogen capture during Leishmania major skin infection

Neutrophils represent one of the first immune cell types recruited to sites of infection, where they can control pathogens by phagocytosis and cytotoxic mechanisms. Intracellular pathogens such as Leishmania major can hijack neutrophils to establish an efficient infection. However the dynamic interactions of neutrophils with the pathogen and other cells at the site of the infection are incompletely understood. Here, we have investigated the role of Ly6G, a homolog of the human CD177 protein, which has been shown to interact with cell adhesion molecules, and serves as a bona fide marker for neutrophils in mice. We show that Ly6G deficiency decreases the initial infection rate of neutrophils recruited to the site of infection. Although the uptake of L. major by subsequently recruited monocytes was tightly linked with the concomitant uptake of neutrophil material, this process was not altered by Ly6G deficiency of the neutrophils. Instead, we observed by intravital 2-photon microscopy that Ly6G-deficient neutrophils entered the site of infection with delayed initial recruitment kinetics. Thus, we conclude that by promoting neutrophils’ ability to efficiently enter the site of infection, Ly6G contributes to the early engagement of intracellular pathogens by the immune system.

Triggering Receptor Expressed on Myeloid Cells-1 Agonist Regulates Intestinal Inflammation via Cd177+ Neutrophils

Triggering receptor expressed on myeloid cell-1 (TREM-1) signaling is expressed on neutrophils and monocytes that is necessary for the successful antimicrobial response and resolution of inflammation in the gut. In this study, we determined the effect of an anti-TREM-1 agonistic antibody (α-TREM-1) on colitis and identify its underlying mechanism of action. Administration of α-TREM-1 alleviated colitis in mice and resolved dysbiosis, which required TLR4/Myd88 signaling. α-TREM-1 increased the production of neutrophil extracellular traps and interleukin-22 by CD177+ neutrophils, which led to pathogen clearance and protection of the intestinal barrier. TREM-1 activation using an α-TREM-1 antibody protects against colitis by rebalancing the microbiota and protecting the epithelium against the immune response as well as modulates the function of neutrophils and macrophages. These results highlight the importance of the TREM-1 pathway in intestinal homeostasis and suggest that α-TREM-1 treatment may be an effective therapeutic strategy for inflammatory bowel disease.

A host-based two-gene model for the identification of bacterial infection in general clinical settings

OBJECTIVES

In this study, we aimed to develop a simple gene model to identify bacterial infection, which can be implemented in general clinical settings.

METHODS

We used a clinically availablereal-time quantitative polymerase chain reaction platform to conduct focused gene expression assays on clinical blood samples. Samples were collected from 2 tertiary hospitals.

RESULTS

We found that the 8 candidate genes for bacterial infection were significantly dysregulated in bacterial infection and displayed good performance in group classification, whereas the 2 genes for viral infection displayed poor performance. A two-gene model (S100A12 and CD177) displayed 93.0% sensitivity and 93.7% specificity in the modeling stage. In the independent validation stage, 87.8% sensitivity and 96.6% specificity were achieved in one set of case-control groups, and 93.6% sensitivity and 97.1% specificity in another set.

CONCLUSIONS

We have validated the signature genes for bacterial infection and developed a two-gene model to identify bacterial infection in general clinical settings.

The immune response after noise damage in the cochlea is characterized by a heterogeneous mix of adaptive and innate immune cells

Cells of the immune system are present in the adult cochlea and respond to damage caused by noise exposure. However, the types of immune cells involved and their locations within the cochlea are unclear. We used flow cytometry and immunostaining to reveal the heterogeneity of the immune cells in the cochlea and validated the presence of immune cell gene expression by analyzing existing single-cell RNA-sequencing (scRNAseq) data. We demonstrate that cell types of both the innate and adaptive immune system are present in the cochlea. In response to noise damage, immune cells increase in number. B, T, NK, and myeloid cells (macrophages and neutrophils) are the predominant immune cells present. Interestingly, immune cells appear to respond to noise damage by infiltrating the organ of Corti. Our studies highlight the need to further understand the role of these immune cells within the cochlea after noise exposure.

Neutrophil heterogeneity and fate in inflamed tissues: implications for the resolution of inflammation

Neutrophils are polymorphonuclear leukocytes that play a central role in host defense against infection and tissue injury. They are rapidly recruited to the inflamed site and execute a variety of functions to clear invading pathogens and damaged cells. However, many of their defense mechanisms are capable of inflicting collateral tissue damage. Neutrophil-driven inflammation is a unifying mechanism underlying many common diseases. Efficient removal of neutrophils from inflammatory loci is critical for timely resolution of inflammation and return to homeostasis. Accumulating evidence challenges the classical view that neutrophils represent a homogeneous population and that halting neutrophil influx is sufficient to explain their rapid decline within inflamed loci during the resolution of protective inflammation. Hence, understanding the mechanisms that govern neutrophil functions and their removal from the inflammatory locus is critical for minimizing damage to the surrounding tissue and for return to homeostasis. In this review, we briefly address recent advances in characterizing neutrophil phenotypic and functional heterogeneity and the molecular mechanisms that determine the fate of neutrophils within inflammatory loci and the outcome of the inflammatory response. We also discuss how these mechanisms may be harnessed as potential therapeutic targets to facilitate resolution of inflammation.

Multiple Roles for Chemokines in Neutrophil Biology

Chemokines are recognized as the most critical mediators for selective neutrophil recruitment during inflammatory conditions. Furthermore, they are considered fundamental regulators of neutrophil mobilization from the bone marrow (BM) to the bloodstream and for their homing back at the end of their life for apoptosis and clearance. However, chemokines are also important mediators of neutrophil effector functions including oxidative burst, degranulation, neutrophil extracellular trap (NET)osis, and production of inflammatory mediators. Neutrophils have been historically considered as a homogeneous population. In recent years, several maturation stages and subsets with different phenotypic profiles and effector functions were described both in physiological and pathological conditions such as infections, autoimmunity, and cancer. The aim of this review is to give an overview of the current evidence regarding the role of chemokines and chemokine receptors in neutrophil biology, including their possible role in neutrophil maturation, differentiation, and in defining emerging neutrophil subsets.

The neutrophil subset defined by CD177 expression is preferentially recruited to gingival crevicular fluid in periodontitis

In recent years, the concept of distinct subpopulations of human neutrophils has attracted much attention. One bona fide subset marker, exclusively expressed by a proportion of circulating neutrophils in a given individual, and therefore dividing neutrophils in two distinct subpopulations, is the glycoprotein CD177. CD177 is expressed on the plasma and granule membranes of 0-100% of circulating neutrophils depending on the donor. Several in vitro studies have linked CD177 to neutrophil transmigration, yet very few have looked at the role of CD177 for tissue recruitment in vivo. We investigate whether the CD177⁺ and CD177^- neutrophil subsets differ in their propensity to migrate to both aseptic- and microbe-triggered inflamed human tissues. Microbe-triggered neutrophil migration was evaluated in samples of gingival crevicular fluid (GCF) from patients with periodontitis, whereas neutrophil migration to aseptic inflammation was evaluated in synovial fluid from patients with inflammatory arthritis, as well as in exudate from experimental skin chambers applied on healthy donors. We found that the proportion of CD177⁺ neutrophils was significantly higher in GCF from patients with periodontitis, as compared to blood from the same individuals. Such accumulation of CD177⁺ neutrophils was not seen in the two models of aseptic inflammation. Moreover, the proportion of CD177⁺ neutrophils in circulation was significantly higher in the periodontitis patient group, as compared to healthy donors. Our data indicate that the CD177⁺ neutrophil subset is preferentially recruited to the gingival crevice of periodontitis patients, and may imply that this subtype is of particular importance for situations of microbe-driven inflammation.

Differential attenuation of β2 integrin-dependent and -independent neutrophil migration by Ly6G ligation

Antibody ligation of the murine neutrophil surface protein Ly6G disrupts neutrophil migration in some contexts but not others. We tested whether this variability reflected divergent dependence of neutrophil migration on β2 integrins, adhesion molecules that interact with Ly6G at the neutrophil surface. In integrin-dependent murine arthritis, Ly6G ligation attenuated joint inflammation, even though mice lacking Ly6G altogether developed arthritis normally. By contrast, Ly6G ligation had no impact on integrin-independent neutrophil migration into inflamed lung. In peritoneum, the role of β2 integrins varied with stimulus, proving dispensable for neutrophil entry in Escherichia coli peritonitis but contributory in interleukin 1 (IL-1)-mediated sterile peritonitis. Correspondingly, Ly6G ligation attenuated only IL-1 peritonitis, disrupting the molecular association between integrins and Ly6G and inducing cell-intrinsic blockade restricted to integrin-dependent migration. Consistent with this observation, Ly6G ligation impaired integrin-mediated postadhesion strengthening for neutrophils arresting on activated cremaster endothelium in vivo. Together, these findings identify selective inhibition of integrin-mediated neutrophil emigration through Ly6G ligation, highlighting the marked site and stimulus specificity of β2 integrin dependence in neutrophil migration.

Identification of the initial molecular changes in response to circulating angiogenic cells-mediated therapy in critical limb ischemia

Background

Critical limb ischemia (CLI) constitutes the most aggressive form of peripheral arterial occlusive disease, characterized by the blockade of arteries supplying blood to the lower extremities, significantly diminishing oxygen and nutrient supply. CLI patients usually undergo amputation of fingers, feet, or extremities, with a high risk of mortality due to associated comorbidities.

Circulating angiogenic cells (CACs), also known as early endothelial progenitor cells, constitute promising candidates for cell therapy in CLI due to their assigned vascular regenerative properties. Preclinical and clinical assays with CACs have shown promising results. A better understanding of how these cells participate in vascular regeneration would significantly help to potentiate their role in revascularization.

Herein, we analyzed the initial molecular mechanisms triggered by human CACs after being administered to a murine model of CLI, in order to understand how these cells promote angiogenesis within the ischemic tissues.

Methods

Balb-c nude mice (n:24) were distributed in four different groups: healthy controls (C, n:4), shams (SH, n:4), and ischemic mice (after femoral ligation) that received either 50 μl physiological serum (SC, n:8) or 5 × 10⁵ human CACs (SE, n:8). Ischemic mice were sacrificed on days 2 and 4 (n:4/group/day), and immunohistochemistry assays and qPCR amplification of Alu-human-specific sequences were carried out for cell detection and vascular density measurements. Additionally, a label-free MS-based quantitative approach was performed to identify protein changes related.

Results

Administration of CACs induced in the ischemic tissues an increase in the number of blood vessels as well as the diameter size compared to ischemic, non-treated mice, although the number of CACs decreased within time. The initial protein changes taking place in response to ischemia and more importantly, right after administration of CACs to CLI mice, are shown.

Conclusions

Our results indicate that CACs migrate to the injured area; moreover, they trigger protein changes correlated with cell migration, cell death, angiogenesis, and arteriogenesis in the host. These changes indicate that CACs promote from the beginning an increase in the number of vessels as well as the development of an appropriate vascular network.

Graphical abstract

Cancer cell-intrinsic function of CD177 in attenuating β-catenin signaling

Aiming to identify immune molecules with a novel function in cancer pathogenesis, we found the cluster of differentiation 177 (CD177), a known neutrophil antigen, to be positively correlated with relapse-free (RFS), metastasis-free (MFS) or overall survival (OS) in breast cancer. Additionally, CD177 expression is correlated with good prognosis in several other solid cancers including prostate, cervical, and lung. Focusing on breast cancer, we found that CD177 is expressed in normal breast epithelial cells and is significantly reduced in invasive cancers. Loss of CD177 leads to hyperproliferative mammary epithelium and contributes to breast cancer pathogenesis. Mechanistically, we found that CD177-deficiency is associated with an increase in β-Catenin signaling. Here we identified CD177 as a novel regulator of mammary epithelial proliferation and breast cancer pathogenesis likely via the modulation of Wnt/β-Catenin signaling pathway, a key signaling pathway involved in multiple cancer types.

Proteomic Profiles in Advanced Age-Related Macular Degeneration Using an Aptamer-Based Proteomic Technology

Purpose

To explore top-ranked plasma proteins related to neovascular age-related macular degeneration (AMD) and geographic atrophy (GA), and explore pathways related to neovascular AMD and GA.

Methods

We conducted a pilot study of patients with neovascular AMD (n = 10), GA (n = 10), and age-matched cataract controls (n = 10) who were recruited into an AMD registry. We measured 4001 proteins in ethylenediaminetetraacetic acid plasma samples using an aptamer-based proteomic technology. Relative concentrations of each of 4001 proteins were log (base 2) transformed and compared between cases of neovascular AMD and GA versus controls using linear regression. Pathway analysis was conducted using pathways downloaded from Reactome.

Results

In this pilot study, higher levels of vinculin and lower levels of CD177 were found in patients with neovascular AMD compared with controls. Neuregulin-4 was higher and soluble intercellular adhesion molecule-1 was lower in patients with GA compared with controls. For neovascular AMD, cargo trafficking to the periciliary membrane, fibroblast growth factor receptor 3b ligand binding and activation, and vascular endothelial growth factor–related pathways were in the top ranked pathways. The top-ranked pathways for GA included several related to ErbB4 signaling.

Conclusions

We found different proteins and different pathways associated with neovascular AMD and GA. Vinculin and some of the top-ranked pathways have been previously associated with AMD, whereas others have not been described.

Translational Relevance

Biomarkers identified in plasma likely reflect systemic alterations in protein expression and may improve our understanding of the mechanisms leading to AMD.

Understanding the Multifaceted Role of Neutrophils in Cancer and Autoimmune Diseases

Neutrophils are one of the first immune cell types that are recruited to injury and infection site. As a vital component of the immune system, neutrophils are heterogeneous immune cells known to have phagocytic property and function in inflammation. Recent studies revealed that neutrophils play dual roles in tumor initiation, development, and progression. The multifunctional roles of neutrophils in diseases are mainly due to their production of different effector molecules under different conditions. N1 and N2 neutrophils or high density neutrophils (HDNs) and low density neutrophils (LDNs) have been used to distinguish neutrophils subpopulations with pro- vs. anti-tumor activity, respectively. Indeed, N1 and N2 neutrophils also represent immunostimulating and immunosuppressive subsets, respectively, in cancer. The emerging studies support their multifaceted roles in autoimmune diseases. Although such subsets are rarely identified in autoimmune diseases, some unique subsets of neutrophils, including low density granulocytes (LDGs) and CD177⁺ neutrophils, have been reported. Given the heterogeneity and functional plasticity of neutrophils, it is necessary to understand the phenotypical and functional features of neutrophils in disease status. In this article, we review the multifaceted activates of neutrophils in cancer and autoimmune diseases, which may support new classification of neutrophils to help understand their important functions in immune homeostasis and pathologies.

Murine host response to Neisseria gonorrhoeae upper genital tract infection reveals a common transcriptional signature, plus distinct inflammatory responses that vary between reproductive cycle phases

Background

The emergence of fully antimicrobial resistant Neisseria gonorrhoeae has led global public health agencies to identify a critical need for next generation anti-gonococcal pharmaceuticals. The development and success of these compounds will rely upon valid pre-clinical models of gonorrhoeae infection. We recently developed and reported the first model of upper genital tract gonococcal infection. During initial characterization, we observed significant reproductive cycle-based variation in infection outcome. When uterine infection occurred in the diestrus phase, there was significantly greater pathology than during estrus phase. The aim of this study was to evaluate transcriptional profiles of infected uterine tissue from mice in either estrus or diestrus phase in order to elucidate possible mechanisms for these differences.

Results

Genes and biological pathways with phase-independent induction during infection showed a chemokine dominant cytokine response to Neisseria gonorrhoeae. Despite general induction being phase-independent, this common anti-gonococcal response demonstrated greater induction during diestrus phase infection. Greater activity of granulocyte adhesion and diapedesis regulators during diestrus infection, particularly in chemokines and diapedesis regulators, was also shown. In addition to a greater induction of the common anti-gonococcal response, Gene Set Enrichment Analysis identified a diestrus-specific induction of type-1 interferon signaling pathways.

Conclusions

This transcriptional analysis of murine uterine gonococcal infection during distinct points in the natural reproductive cycle provided evidence for a common anti-gonococcal response characterized by significant induction of granulocyte chemokine expression and high proinflammatory mediators. The basic biology of this host response to N. gonorrhoeae in estrus and diestrus is similar at the pathway level but varies drastically in magnitude. Overlaying this, we observed type-1 interferon induction specifically in diestrus infection where greater pathology is observed. This supports recent work suggesting this pathway has a significant, possibly host-detrimental, function in gonococcal infection. Together these findings lay the groundwork for further examination of the role of interferons in gonococcal infection. Additionally, this work enables the implementation of the diestrus uterine infection model using the newly characterized host response as a marker of pathology and its prevention as a correlate of candidate vaccine efficacy and ability to protect against the devastating consequences of N. gonorrhoeae-associated sequelae.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5000-7) contains supplementary material, which is available to authorized users.

Polymorphonuclear Neutrophil Functions are Differentially Altered in Amnestic Mild Cognitive Impairment and Mild Alzheimer's Disease Patients

The mechanisms of neurodegeneration in Alzheimer's disease (AD) remain under investigation. Alterations in the blood-brain barrier facilitate exchange of inflammatory mediators and immune cells between the brain and the periphery in AD. Here, we report analysis of phenotype and functions of polymorphonuclear neutrophils (PMN) in peripheral blood from patients with amnestic mild cognitive impairment (aMCI, n = 13), patients with mild AD (mAD, n = 15), and healthy elderly controls (n = 13). Results showed an increased expression of CD177 in mAD but not in healthy or aMCI patients. IL-8 stimulated increased expression of the CD11b integrin in PMN of healthy subjects in vitro but PMN of aMCI and mAD patients failed to respond. CD14 and CD16 expression was lower in PMN of mAD but not in aMCI individuals relative to controls. Only PMN of aMCI subjects expressed lower levels of CD88. Phagocytosis toward opsonized E. coli was differentially impaired in PMN of aMCI and mAD subjects whereas the capacity to ingest Dextran particles was absent only in mAD subjects. Killing activity was severely impaired in aMCI and mAD subjects whereas free radical production was only impaired in mAD patients. Inflammatory cytokine (TNFα, IL-6, IL-1β, IL-12p70) and chemokine (MIP-1α, MIP-1β, IL-8) production in response to LPS stimulation was very low in aMCI and nearly absent in mAD subjects. TLR2 expression was low only in aMCI. Our data showed a differentially altered capacity of PMN of aMCI and mAD subjects to respond to pathological aggression that may impact impaired responses associated with AD development.

Emerging Functions of Regulatory T Cells in Tissue Homeostasis

CD4⁺Foxp3⁺ regulatory T-cells (Tregs) are a unique subset of helper T-cells, which regulate immune response and establish peripheral tolerance. Tregs not only maintain the tone and tenor of an immune response by dominant tolerance but, in recent years, have also been identified as key players in resolving tissue inflammation and as mediators of tissue healing. Apart from being diverse in their origin (thymic and peripheral) and location (lymphoid and tissue resident), Tregs are also phenotypically heterogeneous as per the orientation of ongoing immune response. In this review, we discuss the recent advances in the field of Treg biology in general, and non-lymphoid and tissue-resident Tregs in particular. We elaborate upon well-known visceral adipose tissue, colon, skin, and tumor-infiltrating Tregs and newly identified tissue Treg populations as in lungs, skeletal muscle, placenta, and other tissues. Our attempt is to differentiate Tregs based on distinctive properties of their location, origin, ligand specificity, chemotaxis, and specific suppressive mechanisms. Despite ever expanding roles in maintaining systemic homeostasis, Tregs are employed by large varieties of tumors to dampen antitumor immunity. Thus, a comprehensive understanding of Treg biology in the context of inflammation can be instrumental in effectively managing tissue transplantation, autoimmunity, and antitumor immune responses.

Regulatory T Cells Exhibit Distinct Features in Human Breast Cancer

Regulatory T (Treg) cells reside in lymphoid organs and barrier tissues where they control different types of inflammatory responses. Treg cells are also found in human cancers, and studies in animal models suggest that they contribute to cancer progression. However, properties of human intratumoral Treg cells and those present in corresponding normal tissue remain largely unknown. Here, we analyzed features of Treg cells in untreated human breast carcinomas, normal mammary gland, and peripheral blood. Tumor-resident Treg cells were potently suppressive and their gene-expression pattern resembled that of normal breast tissue, but not of activated peripheral blood Treg cells. Nevertheless, a number of cytokine and chemokine receptor genes, most notably CCR8, were upregulated in tumor-resident Treg cells in comparison to normal tissue-resident ones. Our studies suggest that targeting CCR8 for the depletion of tumor-resident Treg cells might represent a promising immunotherapeutic approach for the treatment of breast cancer.

CD177 modulates human neutrophil migration through activation-mediated integrin and chemoreceptor regulation

CD177 is a glycosylphosphatidylinositol (GPI)-anchored protein expressed by a variable proportion of human neutrophils that mediates surface expression of the antineutrophil cytoplasmic antibody antigen proteinase 3. CD177 associates with β2 integrins and recognizes platelet endothelial cell adhesion molecule 1 (PECAM-1), suggesting a role in neutrophil migration. However, CD177^pos neutrophils exhibit no clear migratory advantage in vivo, despite interruption of in vitro transendothelial migration by CD177 ligation. We sought to understand this paradox. Using a PECAM-1-independent transwell system, we found that CD177^pos and CD177^neg neutrophils migrated comparably. CD177 ligation selectively impaired migration of CD177^pos neutrophils, an effect mediated through immobilization and cellular spreading on the transwell membrane. Correspondingly, CD177 ligation enhanced its interaction with β2 integrins, as revealed by fluorescence lifetime imaging microscopy, leading to integrin-mediated phosphorylation of Src and extracellular signal-regulated kinase (ERK). CD177-driven cell activation enhanced surface β2 integrin expression and affinity, impaired internalization of integrin attachments, and resulted in ERK-mediated attenuation of chemokine signaling. We conclude that CD177 signals in a β2 integrin-dependent manner to orchestrate a set of activation-mediated mechanisms that impair human neutrophil migration.

Heterogeneity Among Neutrophils

Neutrophils (PMNs) play a key role in innate defence mechanisms. Generally, PMNs were considered to have a homogeneous population of mature and diversified cells. It seems, however, that their pleiotropic action results from the existence of different subpopulations in this group of cells. There are data that confirm the involvement of PMNs in the direct activation of other cells in non-specific response, as well as specialised cells in specific response. For example, there have been observations of PMNs with different levels of activity in relation to lymphocytes, and a population was identified which had characteristics similar to those of cells which are capable of presenting antigens. There are also reports of PMNs which demonstrate different survival time or capacity for chemotaxis. Other studies suggest that the neutrophil response to Staphylococcus aureus is diverse (not identical among all neutrophil). There are also reports of PMNs with varying activity during inflammation, which might explain many as yet unknown pathophysiological aspects of their hyperreactivity. The functional dualism of PMNs in the course of neoplastic disorders raises a lot of controversy. This paper presents the current state of knowledge of the heterogeneity of PMNs and their potential roles in different stages of disease.

A sequence-specific polymerase chain reaction method for HNA-2 genotyping: homozygous c.843A>T mutation predicts the absence of CD177

BACKGROUND

Human neutrophil antigen-2 is located on a glycosylphosphatidylinositol-anchored receptor, CD177. Humans not expressing CD177 on their neutrophils may, under defined conditions, form isoantibodies. The genetic background for the absence of CD177 is not fully understood, and genetic screening of patients and donors is currently unavailable. A recent study has documented two mutations associated with CD177 absence: a nonsense polymorphism c.843A>T and a single-base deletion c.1011delG.

STUDY DESIGN AND METHODS

First, we aimed to demonstrate that these newly described mutations are indeed associated with the absence of CD177. DNA fragments from isoimmunized, CD177-negative individuals were sequenced (n = 5). An additional five negative and 10 positive individuals were also analyzed. Second, we aimed to establish a sequence-specific primer (SSP) polymerase chain reaction method for easy and rapid detection of these mutations.

RESULTS

None of 10 CD177-positive individuals, but four of 10 CD177-negative individuals were homozygous for the A>T mutation at Position c.843, including three of five isoimmunized individuals. This finding is supportive for the reported association. Surprisingly, and in contrast to the initial report, c.1011delG was not detected in our cohort. Furthermore, a two-step SSP method for c.843A>G was successfully established.

CONCLUSION

c.843A>T, but not c.1011delG, is associated with the absence of CD177 in a significant number of individuals, including CD177-isoimmunized women. The c.843A>T mutation is easily detectable by a newly established SSP, but screening for this mutation will only provide sufficient evidence for a final diagnosis in case of homozygosity for the c.843T allele.

Neutrophil heterogeneity: implications for homeostasis and pathogenesis

Neutrophils are polymorphonuclear leukocytes of the phagocytic system that act as first line of host defense against invading pathogens but are also important mediators of inflammation-induced injury. In contrast to other members of the innate immune system, neutrophils are classically considered a homogenous population of terminally differentiated cells with a well-defined and highly conserved function. Indeed, their short lifespan, the absent proliferative capacity, their limited ability to produce large amounts of cytokines, and the failure to recirculate from the tissue to the bloodstream have sustained this idea. However, increasing evidence over the last decade has demonstrated an unexpected phenotypic heterogeneity and functional versatility of the neutrophil population. Far beyond their antimicrobial functions, neutrophils are emerging as decision-shapers during innate and adaptive immune responses. These emerging discoveries open a new door to understand the role of neutrophils during homeostatic but also pathogenic immune processes. Thus, this review details novel insights of neutrophil phenotypic and functional heterogeneity during homeostasis and disease.

Organization, evolution and functions of the human and mouse Ly6/uPAR family genes

Members of the lymphocyte antigen-6 (Ly6)/urokinase-type plasminogen activator receptor (uPAR) superfamily of proteins are cysteine-rich proteins characterized by a distinct disulfide bridge pattern that creates the three-finger Ly6/uPAR (LU) domain. Although the Ly6/uPAR family proteins share a common structure, their expression patterns and functions vary. To date, 35 human and 61 mouse Ly6/uPAR family members have been identified. Based on their subcellular localization, these proteins are further classified as GPI-anchored on the cell membrane, or secreted. The genes encoding Ly6/uPAR family proteins are conserved across different species and are clustered in syntenic regions on human chromosomes 8, 19, 6 and 11, and mouse Chromosomes 15, 7, 17, and 9, respectively. Here, we review the human and mouse Ly6/uPAR family gene and protein structure and genomic organization, expression, functions, and evolution, and introduce new names for novel family members.