The neutrophil recombinatorial TCR-like immune receptor is expressed across the entire human life span but repertoire diversity declines in old age

Aberrant expression of T cell receptors in monocyte/macrophage RAW 264.7 cells: FCγRII/III compensates the need for CD3

Conventionally T-cell receptors (TCRs) have so far been considered as a T-lymphocyte privilege. However, recent findings also place TCR expression in non-lymphoid cells, namely neutrophils, eosinophils and macrophages. In order to examine the ectopic expression of TCR, this study focused on RAW 264.7 cells, which have been broadly used for their macrophage properties. Immunofluorescence staining detected 70% and 40% of the cells to express TCRαβ and TCRγδ respectively, which was also verified by RT-PCR experiments and confocal microscopy analysis. Interestingly, except from the predicted 292 and 288 bp gene products for the α- and γ-chain, additional products at 220 and 550 bp could be detected, respectively. RAW 264.7 cells also expressed the co-stimulatory CD4 and CD8 markers at a percentage of 61% and 14% respectively, which supported the expression of TCRs. However, only low numbers of cells expressed CD3ε and CD3ζ (9% and 7% respectively). Such observations contradicted the existing knowledge, and indicated that TCRs would be supported by other molecules for reaching the membrane and transducing their signal. Such candidate molecules could be the Fcγ receptors (FcγRs). Indeed, the FcγRII/III receptor was found to be expressed in 75% of the cells, which also expressed at a percentage of 25% major histocompatibility complex (MHC) class II molecules. Engagement of the FcγRII/III receptor by a recombinant IgG2aCH2 fragment, except from stimulating the macrophage-dependent properties of the cells, was shown to reduce expression of TCRαβ and γδ indicating that FcγRII/III was indeed used by TCRs for their transport to the cell membrane. In order to examine the ability of RAW 264.7 cells to simultaneously display antigen presenting- and T-cell properties, functional experiments as to antigen-specific antibody and IL-2 production were performed. In in vitro immunization assays in the presence of naïve B cells, RAW264.7 failed to promote antibody production. However, RAW 264.7 cells could compete with antigen-stimulated macrophages but not T cells when applied to a system of in vivo antigen-sensitized cells followed by an in vitro immunization protocol. Interestingly, simultaneous addition of antigen and the IgG2aCH2 fragment to RAW 264.7 cells could promote IL-2 production from the cells, indicating that FcγRII/III activation could also support TCR stimulation. Extrapolating these findings to cells of the myeloid origin, the above results dictate novel regulatory mechanisms towards the alteration of the immune response.

Polymorphonuclear Cells Show Features of Dysfunctional Activation During Fatal Sepsis

Sepsis and septic shock remain leading causes of morbidity and mortality for patients in the intensive care unit. During the early phase, immune cells produce various cytokines leading to prompt activation of the immune system. Polymorphonuclear leukocytes (PMNs) respond to different signals producing inflammatory factors and executing their antimicrobial mechanisms, resulting in the engulfment and elimination of invading pathogens. However, excessive activation caused by various inflammatory signals produced during sepsis progression can lead to the alteration of PMN signaling and subsequent defects in their functionality. Here, we analyzed samples from 34 patients in septic shock, focusing on PMNs gene expression and proteome changes associated with septic shock. We revealed that, compared to those patients who survived longer than five days, PMNs from patients who had fulminant sepsis were characterized by a dysfunctional hyper-activation, show altered metabolism, and recent exit from the cell cycle and signs of cellular lifespan. We believe that this multi-omics approach, although limited, pinpoints the alterations in PMNs' functionality, which may be rescued by targeted treatments.

Trilineage Sequencing Reveals Complex TCRβ Transcriptomes in Neutrophils and Monocytes Alongside T Cells

Recent findings indicate the presence of T cell receptor (TCR)-based combinatorial immune receptors beyond T cells in neutrophils and monocytes/macrophages. In this study, using a semiquantitative trilineage immune repertoire sequencing approach as well as under rigorous bioinformatic conditions, we identify highly complex TCRβ transcriptomes in human circulating monocytes and neutrophils that separately encode repertoire diversities one and two orders of magnitude smaller than that of T cells. Intraindividual transcriptomic analyses reveal that neutrophils, monocytes, and T cells express distinct TCRβ repertoires with less than 0.1% overall trilineage repertoire sharing. Interindividual comparison shows that in all three leukocyte lineages, the vast majority of the expressed TCRβ variants are private. We also find that differentiation of monocytes into macrophages induces dramatic individual-specific repertoire shifts, revealing a surprising degree of immune repertoire plasticity in the monocyte lineage. These results uncover the remarkable complexity of the two phagocyte-based flexible immune systems which until now has been hidden in the shadow of T cells.

CyTOF mass cytometry reveals phenotypically distinct human blood neutrophil populations differentially correlated with melanoma stage

Background

Understanding neutrophil heterogeneity and its relationship to disease progression has become a recent focus of cancer research. Indeed, several studies have identified neutrophil subpopulations associated with protumoral or antitumoral functions. However, this work has been hindered by a lack of widely accepted markers with which to define neutrophil subpopulations.

Methods

To identify markers of neutrophil heterogeneity in cancer, we used single-cell cytometry by time-of-flight (CyTOF) coupled with high-dimensional analysis on blood samples from treatment-naïve patients with melanoma.

Results

Our efforts allowed us to identify seven blood neutrophil clusters, including two previously identified individual populations. Interrogation of these neutrophil subpopulations revealed a positive trend between specific clusters and disease stage. Finally, we recapitulated these seven blood neutrophil populations via flow cytometry and found that they exhibited diverse capacities for phagocytosis and reactive oxygen species production in vitro.

Conclusions

Our data provide a refined consensus on neutrophil heterogeneity markers, enabling a prospective functional evaluation in patients with solid tumors.

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.

The Adaptome as Biomarker for Assessing Cancer Immunity and Immunotherapy

In terms of diagnosing and treating diseases, our adaptive immune system is the "best doctor." It carries out these tasks with unmatched precision, with the help of both T and B cell receptors, our most diverse set of genes, distinguishing one individual from another. It does this by generating autologous extraordinary diversity in the receptors, ranging from 10¹⁵ to 10²⁵ for each chain of the rearranged receptors. By combining multiplex PCR and next-generation sequencing (NGS), we have developed high throughput methods to study adaptive immunity. The adaptome is the sum-total of expressed T and B cell receptor genes in a sample, composed of seven chains, including the alpha/beta and gamma/delta chains for T cells, and heavy/lambda or kappa chains for B cells. Immune repertoire is the sum-total of the individual clonotypes within one chain, including individual complementarity-determining regions (CDR) 3 sequences. In order to reflect the breadth and depth of the true adaptome, the following criteria assessing any method needs to be ascertained: (1) Methods need to be inclusive and quantitative; (2) Analysis should consider what questions need to be addressed and whether bulk or single cell sequencing provide the best tools for assessing the underlying biology and addressing important questions; (3) Measures of clonal diversity are key to understand the underlying structure and providence of the repertoire; and (4) Convergent evolution may allow a surprising degree of homologous or identical CDR3s associated with individual disease entities, creating hope for novel diagnostics and/or disease burden assessments. Integrating studies of the peripheral blood, lymph nodes, and tumor allows dynamic interrogation of the alterations occurring with age, treatment, and response to emergent and established therapies.

T Cell Reprogramming Against Cancer

Advances in academic and clinical studies during the last several years have resulted in practical outcomes in adoptive immune therapy of cancer. Immune cells can be programmed with molecular modules that increase their therapeutic potency and specificity. It has become obvious that successful immunotherapy must take into account the full complexity of the immune system and, when possible, include the use of multifactor cell reprogramming that allows fast adjustment during the treatment. Today, practically all immune cells can be stably or transiently reprogrammed against cancer. Here, we review works related to T cell reprogramming, as the most developed field in immunotherapy. We discuss factors that determine the specific roles of αβ and γδ T cells in the immune system and the structure and function of T cell receptors in relation to other structures involved in T cell target recognition and immune response. We also discuss the aspects of T cell engineering, specifically the construction of synthetic T cell receptors (synTCRs) and chimeric antigen receptors (CARs) and the use of engineered T cells in integrative multifactor therapy of cancer.

CD3+ Macrophages Deliver Proinflammatory Cytokines by a CD3- and Transmembrane TNF-Dependent Pathway and Are Increased at the BCG-Infection Site

Macrophages are essential cells of the innate immune response against microbial infections, and they have the ability to adapt under both pro- and anti-inflammatory conditions and develop different functions. A growing body of evidence regarding a novel macrophage subpopulation that expresses CD3 has recently emerged. Here, we explain that human circulating monocytes can be differentiated into CD3⁺TCRαβ⁺ and CD3⁺TCRαβ⁻ macrophages. Both cell subpopulations express on their cell surface HLA family molecules, but only the CD3⁺TCRαβ⁺ macrophage subpopulation co-express CD1 family molecules and transmembrane TNF (tmTNF). CD3⁺TCRαβ⁺ macrophages secrete IL-1β, IL-6 IP-10, and MCP-1 by both tmTNF- and CD3-dependent pathways, while CD3⁺TCRαβ⁻ macrophages specifically produce IFN-γ, TNF, and MIP-1β by a CD3-dependent pathway. In this study, we also used a mouse model of BCG-induced pleurisy and demonstrated that CD3⁺ myeloid cells (TCRαβ⁺ and TCRαβ⁻ cells) are increased at the infection sites during the acute phase (2 weeks post-infection). Interestingly, cell increment was mediated by tmTNF, and the soluble form of TNF was dispensable. BCG-infection also induced the expression of TNF receptor 2 on CD3⁺ myeloid cells, which increased after BCG-infection, suggesting that the tmTNF/TNFRs axis plays an important role in the presence or function of these cells in tuberculosis.

Differential expression of immune-related genes in head kidney and spleen of cobia (Rachycentron canadum) having Streptococcus dysgalactiae infection

Streptococcus dysgalactiae is a gram-positive bacterium and a harmful aquaculture pathogen. To investigate the immune response against S. dysgalactiae, we performed transcriptome analysis of the head kidney and spleen of cobia (Rachycentron canadum) using RNA-seq. Total RNA was extracted from the head kidney and spleen of cobia, 1 and 2 days after treatment with S. dysgalactiae or control PBS. After RNA purification and cDNA library generation, sequencing was performed using the Illumina HiSeq™ 4000 platform. The filtering and de novo assembling transcripts were annotated using several databases. To identify differentially expressed genes (DEGs) between the S. dysgalactiae and PBS groups, the mapped values of fragments per kilobase of transcripts per million fragments were calculated. After de novo assembly, a total of 106,984 transcripts were detected, with an N50 of 3020 bp. These transcripts were annotated and categorised into a total of 7608 genes based on the KEGG pathway database. DEGs (2-fold difference) were calculated by comparing the S. dysgalactiae and PBS control group gene expression levels at each time point. The DEGs were mainly annotated into signal transduction and immune system categories, based on the KEGG database. The DEGs were significantly enriched in the immune-related pathways - "cytokine-cytokine receptor interaction", "complement and coagulation cascades", and "hematopoietic cell linage". In this study, immune-related genes responding to S. dysgalactiae were detected, and several immune system pathways were categorized. We identified the IL17C-related pathway for inducing the expression of pro-inflammatory cytokine genes (IL-1β, IL-6, and IFNγ). Additionally, neutrophil-related genes (CSF3, CD121, and CD114) were induced in the spleen after S. dysgalactiae infection. It was suggested that these pathways contribute to immune responses against S. dysgalactiae infection. The data revealed in this study may offer improved strategies against S. dysgalactiae infection in cobia.

Circulating monocytes and tumor-associated macrophages express recombined immunoglobulins in glioblastoma patients

BACKGROUND

Glioblastoma is the most common and malignant brain tumor in adults. Glioblastoma is usually fatal 12-15 months after diagnosis and the current possibilities in therapy are mostly only palliative. Therefore, new forms of diagnosis and therapy are urgently needed. Since tumor-associated macrophages are key players in tumor progression and survival there is large potential in investigating their immunological characteristics in glioblastoma patients. Recent evidence shows the expression of variable immunoglobulins and TCRαβ in subpopulations of monocytes, in vitro polarized macrophages and macrophages in the tumor microenvironment. We set out to investigate the immunoglobulin sequences of circulating monocytes and tumor-associated macrophages from glioblastoma patients to evaluate their potential as novel diagnostic or therapeutic targets.

RESULTS

We routinely find consistent expression of immunoglobulins in tumor-associated macrophages (TAM) and circulating monocytes from all glioblastoma patients analyzed in this study. However, the immunoglobulin repertoires of circulating monocytes and TAM are generally more restricted compared to B cells. Furthermore, the immunoglobulin expression in the macrophage populations negatively correlates with the tumor volume. Interestingly, the comparison of somatic mutations, V-chain usage, CDR3-length and the distribution of used heavy chain genes on the locus of chromosome 14 of the immunoglobulins from myeloid to B cells revealed virtually no differences.

CONCLUSIONS

The investigation of the immunoglobulin repertoires from TAM and circulating monocytes in glioblastoma-patients revealed a negative correlation to the tumor volume, which could not be detected in the immunoglobulin repertoires of the patients' B lymphocytes. Furthermore, the immunoglobulin repertoires of monocytes were more diverse than the repertoires of the macrophages in the tumor microenvironment from the same patients suggesting a tumor-specific immune response which could be advantageous for the use as diagnostic or therapeutic target.

Immediate Neutrophil-Variable-T Cell Receptor Host Response in Bacterial Meningitis

Bacterial meningitis is a life-threatening disease that evokes an intense neutrophil-dominated host response to microbes invading the subarachnoid space. Recent evidence indicates the existence of combinatorial V(D)J immune receptors in neutrophils that are based on the T cell receptor (TCR). Here, we investigated expression of the novel neutrophil TCRαβ-based V(D)J receptors in cerebrospinal fluid (CSF) from human patients with acute-phase bacterial meningitis using immunocytochemical, genetic immunoprofiling, cell biological, and mass spectrometric techniques. We find that the human neutrophil combinatorial V(D)J receptors are rapidly induced in CSF neutrophils during the first hours of bacterial meningitis. Immune receptor repertoire diversity is consistently increased in CSF neutrophils relative to circulating neutrophils and phagocytosis of baits directed to the variable immunoreceptor is enhanced in CSF neutrophils during acute-phase meningitis. Our results reveal that a flexible immune response involving neutrophil V(D)J receptors which enhance phagocytosis is immediately initiated at the site of acute bacterial infection.

The role of neutrophils in the pathogenesis of atherosclerosis

Atherosclerosis (AS) is one of the causes of cardiovascular disease. The formation of atherosclerotic lesions of the arteries is a long process, and clinical symptoms appear already at the stage of atherosclerotic plaque (ASB), which prevents blood flow and can cause coronary heart disease, as well as acute coronary syndrome. The study of atherosclerosis mechanisms at the subclinical level is relevant. This article provides a summary of current data on the structure and functions of neutrophils (NF) in physiological processes. Particular attention is paid to the participation of neutrophils in the damage and formation of vascular endothelial dysfunction. Discusses several mechanisms of involvement of neutrophils in atherogenesis: the production of reactive oxygen species, which cause direct endothelial damage; the synthesis of cytokines that trigger the migration of leukocytes in inflammation; the formation of protein complexes with cholesterol, contributing to their deposition in the vessels, and neutrophil traps, triggering destructive-alterative reactions.

Expression of combinatorial immunoglobulins in macrophages in the tumor microenvironment

Recent evidence indicates the presence of macrophage subpopulations that express the TCRαβ in chronic inflammatory diseases such as tuberculosis and atherosclerosis and in the tumor microenvironment. Here, we demonstrate that a second subpopulation of macrophages expresses rearranged heavy and light chain immunoglobulins. We identify immunoglobulin expression in human and murine monocytes, in ex vivo differentiated macrophages and macrophages from the tumor microenvironment of five randomly selected distinct human tumor entities. The immunoglobulin heavy and light chains are expressed in a small macrophage subfraction (~3-5%) as combinatorial and individual-specific immune receptors. Using Sanger sequencing and deep sequencing, we routinely find markedly restricted Ig repertoires in monocytes/macrophages compared to normal B cells. Furthermore, we report the complete Ig heavy and light chain sequences of a fully functional immunoglobulin from a single tumor-associated macrophage. These results demonstrate that Ig expression is a defining feature of monocytes and also macrophages in the tumor microenvironment and thus reveal an as yet unrecognized modus operandi of host defense in professional phagocytes.

Immune System Dysfunction in the Elderly

Human aging is characterized by both physical and physiological frailty that profoundly affects the immune system. In this context aging is associated with declines in adaptive and innate immunity established as immunosenescence. Immunosenescence is a new concept that reflects the age-associated restructuring changes of innate and adaptive immune functions. Thus elderly individuals usually present chronic low-level inflammation, higher infection rates and chronic diseases. A study of alterations in the immune system during aging could provide a potentially useful biomarker for the evaluation of immune senescence treatment. The immune system is the result of the interplay between innate and adaptive immunity, yet the impact of aging on this function is unclear. In this article the function of the immune system during aging is explored.

Neutrophil programming dynamics and its disease relevance

Neutrophils are traditionally considered as first responders to infection and provide antimicrobial host defense. However, recent advances indicate that neutrophils are also critically involved in the modulation of host immune environments by dynamically adopting distinct functional states. Functionally diverse neutrophil subsets are increasingly recognized as critical components mediating host pathophysiology. Despite its emerging significance, molecular mechanisms as well as functional relevance of dynamically programmed neutrophils remain to be better defined. The increasing complexity of neutrophil functions may require integrative studies that address programming dynamics of neutrophils and their pathophysiological relevance. This review aims to provide an update on the emerging topics of neutrophil programming dynamics as well as their functional relevance in diseases.

THE NEW LOOK AT NEUTROPHILIC GRANULOCYTES: RETHINKING OLD DOGMAS. PART 1

Numerous modern basic research done undeniable fact that neutrophilic granulocytes (NG) are key effector and regulatory circuits both innate and adaptive immunity, and play a crucial role in the pathogenesis of a wide range of diseases. NG have potent receptor repertoire, providing a connection between them, cells of the immune system, as well as communication with endothelial cells, epithelial and other tissues. NG inducing stimuli activate and promote the translocation of cytoplasmic granules and vesicles surface molecules on the cytoplasmic membrane the secretion of a large spectrum of pro-and anti-inf lammatory, immunoregulatory cytokines, colony, angiogenic factors and fibrogenic, TNF superfamily members, chemokines, regulatory protein, etc. Chromatin nuclei NG capable of restructuring under the influence of inducing stimuli, which is associated with the expression of multiple cytokine genes. NG receiving complex cytokine inf luence not only acquire new features, but also in various stages of activation and differentiation processes involved in intracellular intraphagosomalis degranulation and killing of implementing elimination microorganisms and extracellular neutrophil degranulation in the formation neutrophil extracellular traps (NET), while this dying through NETosis. Features NG phenotype and their functional properties, demonstrate the existence of subpopulations of NG with different capabilities: equipment of different receptor, the ability to restructure chromatin expressing cytokine genes and secrete cytokines to implement the contents of the granular system, produce reactive oxygen species, implement cytotoxicity form NET. In our opinion, there subpopulation NG: regulatory; suppressor; proinf lammatory — initiating an inf lammatory response; inf lammation with a positive potential microbicidal (antibacterial, antiviral, antifungal); inf lammatory cytotoxic potential of the negative  — “aggressive”; anti-inf lammation regulating regression; antitumoral — TAN1; pro-tumoral — TAN2; hybrid, combining the characteristics of NG and dendritic cells. The absence of adequate response, or hyperactivation blockade NG functions leads to the development of low-intensity infectious and inf lammatory diseases, do not respond to conventional therapy of autoimmune diseases/chronic immune-dependent processes. Remodeling dysfunctions NG — the key to new immunotherapeutic strategies.

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.

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.

Mitochondrial and oxidative stress genes are differentially expressed in neutrophils of sJIA patients treated with tocilizumab: a pilot microarray study

BACKGROUND

Various pathways involved in the pathogenesis of sJIA have been identified through gene expression profiling in peripheral blood mononuclear cells (PBMC), but not in neutrophils. Since neutrophils are important in tissue damage during inflammation, and are elevated as part of the acute phase response, we hypothesised that neutrophil pathways could also be important in the pathogenesis of sJIA. We therefore studied the gene profile in both PBMC and neutrophils of sJIA patients treated with tocilizumab.

METHODS

We studied the transcriptomes of peripheral blood mononuclear cells (PBMC) and neutrophils from eight paired samples obtained from 4 sJIA patients taken before and after treatment, selected on the basis that they achieved ACR90 responses within 12 weeks of therapy initiation with tocilizumab. RNA was extracted and gene expression profiling was performed using Affymetrix GeneChip Human Genome U133 Plus 2.0 microarray platform. A longitudinal analysis using paired t-test (p < 0.05 and FC ≥ 1.5) was applied to identify differentially expressed genes (DEGs) between the two time points followed by ingenuity pathway analysis. Gene Set Enrichment Analysis (GSEA) and quantitative real-time PCR were then performed to verify the microarray results.

RESULTS

Gene ontology analysis in neutrophils revealed that response to tocilizumab significantly altered genes regulating mitochondrial dysfunction and oxidative stress (p = 4.6E-05). This was independently verified with GSEA, by identifying a set of oxidative genes whose expression correlated with response to tocilizumab. In PBMC, treatment of sJIA with tocilizumab appeared to affect genes in Oncostatin M signalling and B cell pathways.

CONCLUSIONS

For the first time we demonstrate that neutrophils from sJIA patients responding to tocilizumab showed significantly different changes in gene expression. These data could highlight the importance of mitochondrial genes that modulate oxidative stress in the pathogenesis of sJIA.

A combinatorial αβ T cell receptor expressed by macrophages in the tumor microenvironment

Recent evidence indicates the presence of macrophage subpopulations that express the TCRαβ in two major inflammatory diseases, tuberculosis and atherosclerosis. Inflammation is also a well-established attribute of cancer progression and macrophages are one of the major immune cells that infiltrate tumors. Here, we demonstrate that the macrophage-TCRαβ is expressed in the tumor microenvironment of human and murine malignancies. We identify TCRαβ⁺ macrophages in each case of four randomly selected distinct human tumor entities. In human tumor tissues, the TCRαβ expressed by macrophages in the tumor microenvironment is a combinatorial and individual-specific immune receptor. Furthermore, we routinely find TCRαβ⁺ macrophage subpopulations in experimental tumors (TS/A, mammary adenocarcinoma) which we induced both in normal mice and mice deficient in the macrophage receptor stabilin-1. Expression of the combinatorial murine tumor macrophage TCRαβ is individual-specific and independent of stabilin-1. These results demonstrate that TCRαβ expression is a characteristic feature of macrophages in the tumor microenvironment and identify an as yet unrecognized flexible element in the macrophage-based host response to tumors.

The macrophage-TCRαβ is a cholesterol-responsive combinatorial immune receptor and implicated in atherosclerosis

Recent evidence indicates constitutive expression of a recombinatorial TCRαβ immune receptor in mammalian monocytes and macrophages. Here, we demonstrate in vitro that macrophage-TCRβ repertoires are modulated by atherogenic low density cholesterol (LDL) and high-density cholesterol (HDL). In vivo, analysis of freshly obtained artery specimens from patients with severe carotid atherosclerosis reveals massive abundance of TCRαβ(+) macrophages within the atherosclerotic lesions. Experimental atherosclerosis in mouse carotids induces accumulation of TCR bearing macrophages in the vascular wall and TCR deficient rag(-/-) mice have an altered macrophage-dependent inflammatory response. We find that the majority of TCRαβ bearing macrophages are localized in the hot spot regions of the atherosclerotic lesions. Advanced carotid artery lesions express highly restricted TCRαβ repertoires that are characterized by a striking usage of the Vβ22 and Vβ16 chains. This together with a significant degree of interindividual lesion repertoire sharing suggests the existence of atherosclerosis-associated TCRαβ signatures. Our results implicate the macrophage-TCRαβ combinatorial immunoreceptor in atherosclerosis and thus identify an as yet unknown adaptive component in the innate response-to-injury process that underlies this macrophage-driven disease.

Social networking of human neutrophils within the immune system

It is now widely recognized that neutrophils are highly versatile and sophisticated cells that display de novo synthetic capacity and may greatly extend their lifespan. In addition, concepts such as "neutrophil heterogeneity" and "neutrophil plasticity" have started to emerge, implying that, under pathological conditions, neutrophils may differentiate into discrete subsets defined by distinct phenotypic and functional profiles. A number of studies have shown that neutrophils act as effectors in both innate and adaptive immunoregulatory networks. In fact, once recruited into inflamed tissues, neutrophils engage into complex bidirectional interactions with macrophages, natural killer, dendritic and mesenchymal stem cells, B and T lymphocytes, or platelets. As a result of this cross-talk, mediated either by contact-dependent mechanisms or cell-derived soluble factors, neutrophils and target cells reciprocally modulate their survival and activation status. Altogether, these novel aspects of neutrophil biology have shed new light not only on the potential complex roles that neutrophils play during inflammation and immune responses, but also in the pathogenesis of several inflammatory disorders including infection, autoimmunity, and cancer.

A second combinatorial immune receptor in monocytes/macrophages is based on the TCRγδ

Recent evidence indicates that monocytes and macrophages express T cell receptor (TCR)αβ-like combinatorial immune receptors. Here, we demonstrate the presence of a second recombinatorial immunoreceptor, which is structurally based on the TCR γ- and δ-chains, in human and murine monocytes and differentially activated macrophages (referred to here as TCRL(m)γδ). In vitro, infection of macrophages with mycobacteria and gram positive or gram negative bacteria induced expression of donor-specific and differential TCRL(m)Vδ repertoires indicating that the novel immunoreceptor represents a dynamic flexible host defense system that responds to bacterial challenge. In vivo, we find that TCRL(m)γδ bearing macrophages, which express highly restricted repertoires of the antigen-binding Vδ chain, accumulate in the cerebrospinal fluid in acute bacterial meningitis and in advanced lesions of atherosclerosis. These results identify an as yet unrecognized monocyte/macrophage subpopulation that bears combinatorial TCRL(m)γδ immune receptors, and is associated with both acute and chronic inflammatory diseases. Moreover, they indicate that the monocytic lineage uses the same bipartite system of TCRαβ/TCRγδ-based combinatorial immune receptors that is present in T cells. Our findings suggest specific roles of monocytes/macrophages in various inflammatory conditions and lend further evidence that flexible immune recognition in higher vertebrates operates on a broader cellular basis than previously thought.

On the horizon: flexible immune recognition outside lymphocytes

Since decades there is consensus among immunologists that in jawless and jawed vertebrates flexible immune recognition is strictly confined to the lymphoid lineage. In jawed vertebrates the adaptive immune system is represented by two lineages of lymphocytes, B cells and T cells that express recombinatorial antigen receptors of enormous diversity known as immunoglobulins and the T cell receptor (TCR). The recent identification of recombined immune receptors that are structurally based on the TCR in subpopulations of neutrophils and eosinophils (referred to here as TCR-like immunoreceptors, "TCRL") provides unexpected evidence for the existence of flexible host defense mechanisms beyond the realm of lymphocytes. Consistent with this, subpopulations of monocytes and macrophages from humans and mice now have also been shown to constitutively express recombined TCR-like immunoreceptors. Available in vitro evidence suggests that the TCRL in macrophages may exert functions as facilitators of phagocytosis and self-recruitment. More importantly, our recent findings that the macrophage-TCRL is implicated in granuloma formation in tuberculosis and the neutrophil-TCRL is associated with autoimmune hemolytic anemia establish for the first time a link between myeloid recombinatorial immune receptors and clinical disease. The discovery of recombined TCR-like immune receptors in granulocytes and macrophages extends the principle of combinatorial immune recognition to phagocytic cells. Conceptually, this unifies the two hitherto disparate cardinal features of innate and adaptive immunity, phagocytic capacity and recombinatorial immune recognition on a common cellular platform. Moreover, it strongly suggests that flexible host defense in vertebrates may operate on a broader cellular basis than currently thought.