Keratinocytes present Staphylococcus aureus enterotoxins and promote malignant and non-malignant T cell proliferation in cutaneous T cell lymphoma.

Cutaneous T-cell lymphoma (CTCL) is characterized by malignant T-cells proliferating in a unique tumor microenvironment (TME) dominated by keratinocytes. Skin colonization and infection by Staphylococcus aureus (S. aureus) is a common cause of morbidity and suspected of fueling disease activity. Here we show that expression of HLA-DR, high-affinity receptors for Staphylococcal enterotoxins (SE), by keratinocytes correlates with IFN-γ expression in the TME. Importantly, IFN-γ induces HLA-DR, SE-binding, and SE-presentation by keratinocytes to malignant T-cells from Sézary syndrome (SS) patients, and malignant and non-malignant T-cell lines derived from SS and Mycosis fungoides patients. Likewise, preincubation of keratinocytes with supernatant from patient-derived SE-producing S. aureus triggers proliferation in malignant T-cells and cytokine release (including IL-2), when cultured with non-malignant T-cells. This is inhibited by pre-treatment with engineered bacteriophage S. aureus-specific endolysins. Furthermore, mutations in the HLA-DR binding sites of SE type-A, and siRNA-mediated knockdown of Janus Kinase-3 (JAK3) and IL-2Rγ block induction of malignant T-cell proliferation. In conclusion, we show that, upon exposure to patient-derived S. aureus and SE, keratinocytes stimulate IL-2Rγ/JAK3-dependent proliferation of malignant and non-malignant T-cells in an environment with non-malignant T-cells. These findings suggest that keratinocytes in the TME play a key role in S. aureus mediated disease activity in CTCL.

Large overlap in neutrophil transcriptome between lupus and COVID-19 with limited lupus-specific gene expression.

OBJECTIVES: To illuminate the poorly understood aetiology of SLE by comparing the gene expression profile of SLE neutrophils with that of neutrophils from patients infected by SARS-CoV-2, a disease (COVID-19) with well-defined antigens and a similar type I interferon response. METHODS: RNA sequencing of neutrophils from patients with SLE (n=15) and healthy controls (n=12) was analysed for differential gene expression and modulated pathways. The same analyses were performed on a similar neutrophil dataset from patients with SARS-CoV-2 infection (n=30) and healthy controls (n=8). Next, we carried out comparative analyses to identify common and unique transcriptional changes between the two disease contexts, emphasising genes regulated in opposite directions. RESULTS: We identified 372 differentially expressed genes in SLE neutrophils compared with healthy donor neutrophils (≥2 fold, p<0.05), 181 of which were concordant with transcriptional changes in SARS-CoV-2-infected individuals compared with their respective healthy controls. In contrast, 118 genes demonstrated statistically significant alterations exclusive to SLE, including 28 genes that were differentially expressed in opposite directions in the two diseases. CONCLUSIONS: The substantial overlap between neutrophil responses in SLE and COVID-19 suggests that the unknown cause of SLE is functionally similar to a viral infection and drives a similar immune activation and type I interferon response. Conversely, the genes regulated in the opposite direction represent responses unique to SLE. These include tyrosylprotein sulfotransferase-1 and nucleic acid deaminases of the APOBEC family, which can catalyse cytosine-to-uridine editing of both RNA and DNA, and other RNA-modifying enzymes.

Prediction of alternative pre-mRNA splicing outcomes.

To understand the biological impact of alternative pre-mRNA splicing, it is vital to know which exons are involved, what protein domains they encode, and how the translated isoforms differ. Therefore, we developed a computational pipeline (RiboSplitter) focused on functional effect prediction. It builds on event-based alternative splicing detection with additional filtering steps leading to more efficient statistical testing, and with detection of isoform-specific protein changes. A key methodological advance is reading frame prediction by translating exonic DNA in all possible frames, then finding a single open reading frame, or a single frame with matches to known proteins of the gene. This allowed unambiguous translation in 93.9% of alternative splicing events when tested on RNA-sequencing data of B cells from Sjögren's syndrome patients. RiboSplitter does not depend on reference annotations and translates events even when one or both isoform(s) are novel (unannotated). RiboSplitter's visualizations illustrate each event with translation outcomes, show event location within the gene, and align exons to protein domains.

Ultrasensitive Detection of Circulating LINE-1 ORF1p as a Specific Multicancer Biomarker.

Improved biomarkers are needed for early cancer detection, risk stratification, treatment selection, and monitoring treatment response. Although proteins can be useful blood-based biomarkers, many have limited sensitivity or specificity for these applications. Long INterspersed Element-1 (LINE-1) open reading frame 1 protein (ORF1p) is a transposable element protein overexpressed in carcinomas and high-risk precursors during carcinogenesis with negligible expression in normal tissues, suggesting ORF1p could be a highly specific cancer biomarker. To explore ORF1p as a blood-based biomarker, we engineered ultrasensitive digital immunoassays that detect mid-attomolar (10-17 mol/L) ORF1p concentrations in plasma across multiple cancers with high specificity. Plasma ORF1p shows promise for early detection of ovarian cancer, improves diagnostic performance in a multianalyte panel, provides early therapeutic response monitoring in gastroesophageal cancers, and is prognostic for overall survival in gastroesophageal and colorectal cancers. Together, these observations nominate ORF1p as a multicancer biomarker with potential utility for disease detection and monitoring. SIGNIFICANCE: The LINE-1 ORF1p transposon protein is pervasively expressed in many cancers and is a highly specific biomarker of multiple common, lethal carcinomas and their high-risk precursors in tissue and blood. Ultrasensitive ORF1p assays from as little as 25 µL plasma are novel, rapid, cost-effective tools in cancer detection and monitoring. See related commentary by Doucet and Cristofari, p. 2502. This article is featured in Selected Articles from This Issue, p. 2489.

Expression of Envelope Protein Encoded by Endogenous Retrovirus K102 in Rheumatoid Arthritis Neutrophils.

Many patients suffering from autoimmune diseases have autoantibodies against proteins encoded by genomic retroelements, suggesting that normal epigenetic silencing is insufficient to prevent the production of the encoded proteins for which immune tolerance appears to be limited. One such protein is the transmembrane envelope (Env) protein encoded by human endogenous retrovirus K (HERV-K). We reported recently that patients with rheumatoid arthritis (RA) have IgG autoantibodies that recognize Env. Here, we use RNA sequencing of RA neutrophils to analyze HERV-K expression and find that only two loci with an intact open-reading frame for Env, HERV-K102, and K108 are expressed, but only the former is increased in RA. In contrast, other immune cells express more K108 than K102. Patient autoantibodies recognized endogenously expressed Env in breast cancer cells and in RA neutrophils but not healthy controls. A monoclonal anti-Env antibody also detected Env on the surface of RA neutrophils but very little on the surface of other immune cells. We conclude that HERV-K102 is the locus that produces Env detectable on the surface of neutrophils in RA. The low levels of HERV-K108 transcripts may contribute only marginally to cell surface Env on neutrophils or other immune cells in some patients.

Tozorakimab (MEDI3506): an anti-IL-33 antibody that inhibits IL-33 signalling via ST2 and RAGE/EGFR to reduce inflammation and epithelial dysfunction.

Interleukin (IL)-33 is a broad-acting alarmin cytokine that can drive inflammatory responses following tissue damage or infection and is a promising target for treatment of inflammatory disease. Here, we describe the identification of tozorakimab (MEDI3506), a potent, human anti-IL-33 monoclonal antibody, which can inhibit reduced IL-33 (IL-33red) and oxidized IL-33 (IL-33ox) activities through distinct serum-stimulated 2 (ST2) and receptor for advanced glycation end products/epidermal growth factor receptor (RAGE/EGFR complex) signalling pathways. We hypothesized that a therapeutic antibody would require an affinity higher than that of ST2 for IL-33, with an association rate greater than 107 M-1 s-1, to effectively neutralize IL-33 following rapid release from damaged tissue. An innovative antibody generation campaign identified tozorakimab, an antibody with a femtomolar affinity for IL-33red and a fast association rate (8.5 × 107 M-1 s-1), which was comparable to soluble ST2. Tozorakimab potently inhibited ST2-dependent inflammatory responses driven by IL-33 in primary human cells and in a murine model of lung epithelial injury. Additionally, tozorakimab prevented the oxidation of IL-33 and its activity via the RAGE/EGFR signalling pathway, thus increasing in vitro epithelial cell migration and repair. Tozorakimab is a novel therapeutic agent with a dual mechanism of action that blocks IL-33red and IL-33ox signalling, offering potential to reduce inflammation and epithelial dysfunction in human disease.

Expression of L1 retrotransposons in granulocytes from patients with active systemic lupus erythematosus.

BACKGROUND: Patients with systemic lupus erythematosus (SLE) have autoantibodies against the L1-encoded open-reading frame 1 protein (ORF1p). Here, we report (i) which immune cells ORF1p emanates from, (ii) which L1 loci are transcriptionally active, (iii) whether the cells express L1-dependent interferon and interferon-stimulated genes, and (iv) the effect of inhibition of L1 ORF2p by reverse transcriptase inhibitors. RESULTS: L1 ORF1p was detected by flow cytometry primarily in SLE CD66b+CD15+ regular and low-density granulocytes, but much less in other immune cell lineages. The amount of ORF1p was higher in neutrophils from patients with SLE disease activity index (SLEDAI) > 6 (p = 0.011) compared to patients with inactive disease, SLEDAI < 4. Patient neutrophils transcribed seven to twelve human-specific L1 loci (L1Hs), but only 3 that are full-length and with an intact ORF1. Besides serving as a source of detectable ORF1p, the most abundant transcript encoded a truncated ORF2p reverse transcriptase predicted to remain cytosolic, while the two other encoded an intact full-length ORF2p. A number of genes encoding proteins that influence L1 transcription positively or negatively were altered in patients, particularly those with active disease, compared to healthy controls. Components of nucleic acid sensing and interferon induction were also altered. SLE neutrophils also expressed type I interferon-inducible genes and interferon ß, which were substantially reduced after treatment of the cells with drugs known to inhibit ORF2p reverse transcriptase activity. CONCLUSIONS: We identified L1Hs loci that are transcriptionally active in SLE neutrophils, and a reduction in the epigenetic silencing mechanisms that normally counteract L1 transcription. SLE neutrophils contained L1-encoded ORF1p protein, as well as activation of the type I interferon system, which was inhibited by treatment with reverse transcriptase inhibitors. Our findings will enable a deeper analysis of L1 dysregulation and its potential role in SLE pathogenesis.

Argonaute, Vault, and Ribosomal Proteins Targeted by Autoantibodies in Systemic Lupus Erythematosus.

OBJECTIVE: To expand, in an unbiased manner, our knowledge of autoantigens and autoantibodies in patients with systemic lupus erythematosus (SLE) and evaluate their associations with serological and clinical variables. METHODS: Human proteome arrays (> 21,000 proteins) were screened with serum from patients with SLE (n = 12) and healthy controls (n = 6) for IgG and IgA binding. Top hits were validated with 2 cohorts of patients with SLE (cohort 1, n = 49; cohort 2, n = 46) and other rheumatic diseases by ELISA. Clinical associations of the autoantibodies were tested. RESULTS: Ro60 was the top hit in the screen, and the 10 following proteins included 2 additional known SLE autoantigens plus 8 novel autoantigens involved in microRNA processing (Argonaute protein 1 [AGO1], AGO2, and AGO3), ribosomes (ribosomal protein lateral stalk subunit P2 and ovarian tumor deubiquitinase 5 [OTUD5]), RNA transport by the vault (major vault protein), and the immune proteasome (proteasome activator complex subunit 3). Patient serum contained IgG reactive with these proteins and IgA against the AGO proteins. Using the 95th percentile of healthy donor reactivity, 5-43% were positive for the novel antigens, with OTUD5 and AGO1 showing the highest percentages of positivity. Autoantibodies against AGO1 proteins were more prevalent in patients with oral ulcers in a statistically significant manner. IgG autoantibodies against AGO proteins were also seen in other rheumatic diseases. CONCLUSION: We discovered new autoantigens existing in cytosolic macromolecular protein assemblies containing RNA (except the proteasome) in cells. A more comprehensive list of autoantigens will allow for a better analysis of how proteins are targeted by the autoimmune response. Future research will also reveal whether specific autoantibodies have utility in the diagnosis or management of SLE.

Ultrasensitive detection of circulating LINE-1 ORF1p as a specific multi-cancer biomarker.

Improved biomarkers are needed for early cancer detection, risk stratification, treatment selection, and monitoring treatment response. While proteins can be useful blood-based biomarkers, many have limited sensitivity or specificity for these applications. Long INterspersed Element-1 (LINE-1, L1) open reading frame 1 protein (ORF1p) is a transposable element protein overexpressed in carcinomas and high-risk precursors during carcinogenesis with negligible detectable expression in corresponding normal tissues, suggesting ORF1p could be a highly specific cancer biomarker. To explore the potential of ORF1p as a blood-based biomarker, we engineered ultrasensitive digital immunoassays that detect mid-attomolar (10-17 M) ORF1p concentrations in patient plasma samples across multiple cancers with high specificity. Plasma ORF1p shows promise for early detection of ovarian cancer, improves diagnostic performance in a multi-analyte panel, and provides early therapeutic response monitoring in gastric and esophageal cancers. Together, these observations nominate ORF1p as a multi-cancer biomarker with potential utility for disease detection and monitoring.

Neutrophil activation in patients with anti-neutrophil cytoplasmic autoantibody-associated vasculitis and large-vessel vasculitis.

OBJECTIVE: To assess markers of neutrophil activation such as calprotectin and N-formyl methionine (fMET) in anti-neutrophil cytoplasmic autoantibody-associated vasculitis (AAV) and large-vessel vasculitis (LVV). METHODS: Levels of fMET, and calprotectin, were measured in the plasma of healthy controls (n=30) and patients with AAV (granulomatosis with polyangiitis (GPA, n=123), microscopic polyangiitis (MPA, n=61)), and LVV (Takayasu's arteritis (TAK, n=58), giant cell arteritis (GCA, n=68)), at times of remission or flare. Disease activity was assessed by physician global assessment. In vitro neutrophil activation assays were performed in the presence or absence of formyl peptide receptor 1 (FPR1) inhibitor cyclosporine H. RESULTS: Levels of calprotectin, and fMET were elevated in patients with vasculitis as compared to healthy individuals. Levels of fMET correlated with markers of systemic inflammation: C-reactive protein (r=0.82, p<0.0001), and erythrocyte sedimentation rate (r=0.235, p<0.0001). The neutrophil activation marker, calprotectin was not associated with disease activity. Circulating levels of fMET were associated with neutrophil activation (p<0.01) and were able to induce de novo neutrophil activation via FPR1-mediated signaling. CONCLUSION: Circulating fMET appears to propagate neutrophil activation in AAV and LVV. Inhibition of fMET-mediated FPR1 signaling could be a novel therapeutic intervention for systemic vasculitides.

Autoantibodies against the envelope proteins of endogenous retroviruses K102 and K108 in patients with systemic lupus erythematosus correlate with active disease.

OBJECTIVES: To determine if patients with systemic lupus erythematosus (SLE), a disease characterised by elevated type I interferons reminiscent of anti-viral immunity, have expression of human endogenous retrovirus K (HERV-K) proviruses capable of producing envelope (Env) protein, as well as associated autoantibodies against the Env protein. METHODS: ELISAs were conducted with recombinant Env protein and sera from SLE patients with active (n=60) or inactive (n=49) disease, healthy controls (n=47), other rheumatic disorders (n=59), as well as plasma from paediatric lupus patients with active (n=30) or inactive (n=30) disease, and 17 healthy children. Antibody reactivity was evaluated for correlations with clinical and laboratory parameters of the patients. Expression of HERV-K transcripts were profiled in SLE leukocytes by RNA-Seq. RESULTS: Both adult and paediatric SLE patients had autoantibodies against HERV-K Env with higher titres than healthy controls or patients with Sjögren's syndrome, small- or large-vessel vasculitis, or psoriatic arthritis. Transcripts from only two HERV-K loci capable of producing Env, HERV-K102 and -K108, were detected among the 10 expressed loci in SLE patients. CONCLUSIONS: Our data reveal that HERV-K proviruses are expressed in SLE and that the HERV-K-encoded Env protein elicits an immune response in patients, particularly during active disease.

Autoantibodies Against Unmodified and Citrullinated Human Endogenous Retrovirus K Envelope Protein in Patients With Rheumatoid Arthritis.

OBJECTIVE: Autoantibodies against proteins encoded by human endogenous retrovirus K (HERV-K) have been reported in patients with rheumatoid arthritis (RA), but their relevance, if any, has remained unresolved. We revisited this question and tested if such autoantibodies may react with citrullinated epitopes on the envelope (Env) protein of HERV-K. METHODS: Immunoblotting and ELISAs were conducted with unmodified Env protein and with Env citrullinated by protein arginine deiminase 4 (PAD4). Sera from 100 patients with RA, plasma from 32 patients with juvenile idiopathic arthritis (JIA), and healthy adult and pediatric controls were included. Antibody reactivity was evaluated for correlations with clinical and laboratory variables of the patients. RESULTS: We replicated and expanded upon published data suggesting that patients with RA or JIA have autoantibodies against HERV-K Env, some with high titers. Anti-HERV-K antibodies correlated with cigarette smoking and with circulating myeloperoxidase-DNA complexes indicative of nonapoptotic neutrophil cell death. Further, most of the patients with RA, but not those with JIA, had autoantibodies that reacted more strongly with Env that was citrullinated by PAD4. These anticitrullinated Env autoantibodies correlated with seropositivity and tended to be higher in patients with erosive disease. CONCLUSION: Our data suggest that anti-HERV-K immunity is elevated in RA and JIA and may have a connection with pathogenic protein citrullination in RA.

Allergic Aspects of IgG4-Related Disease: Implications for Pathogenesis and Therapy.

IgG4-related disease (IgG4-RD) is a rare systemic fibroinflammatory disease frequently associated with allergy. The pathogenesis of IgG4-RD is poorly understood, and effective therapies are limited. However, IgG4-RD appears to involve some of the same pathogenic mechanisms observed in allergic disease, such as T helper 2 (Th2) and regulatory T cell (Treg) activation, IgG4 and IgE hypersecretion, and blood/tissue eosinophilia. In addition, IgG4-RD tissue fibrosis appears to involve activation of basophils and mast cells and their release of alarmins and cytokines. In this article, we review allergy-like features of IgG4-RD and highlight targeted therapies for allergy that have potential in treating patients with IgG4-RD.

IgG and IgA autoantibodies against L1 ORF1p expressed in granulocytes correlate with granulocyte consumption and disease activity in pediatric systemic lupus erythematosus.

BACKGROUND: Most patients with systemic lupus erythematosus (SLE) have IgG autoantibodies against the RNA-binding p40 (ORF1p) protein encoded by the L1 retroelement. This study tested if these autoantibodies are also present in children with pediatric SLE (pSLE) and if the p40 protein itself could be detected in immune cells. METHODS: Autoantibodies in the plasma of pSLE patients (n = 30), healthy children (n = 37), and disease controls juvenile idiopathic arthritis (JIA) (n = 32) and juvenile dermatomyositis (JDM) (n = 60), were measured by ELISA. Expression of p40 in immune cells was assessed by flow cytometry. Markers of neutrophil activation and death were quantitated by ELISA. RESULTS: IgG and IgA autoantibodies reactive with p40 were detected in the pSLE patients, but were low in healthy controls and in JIA or JDM. pSLE patients with active disease (13 of them newly diagnosed) had higher titers than the same patients after effective therapy (p = 0.0003). IgG titers correlated with SLEDAI (r = 0.65, p = 0.0001), ESR (r = 0.43, p = 0.02), and anti-dsDNA antibodies (r = 0.49, p < 0.03), and inversely with complement C3 (r = -0.55, p = 0.002) and C4 (r = -0.51, p = 0.006). p40 protein was detected in a subpopulation of CD66b+ granulocytes in pSLE, as well as in adult SLE patients. Myeloperoxidase and neutrophil elastase complexed with DNA and the neutrophil-derived S100A8/A9 were elevated in plasma from pSLE patients with active disease and correlated with anti-p40 autoantibodies and disease activity. CONCLUSIONS: Children with active SLE have elevated IgG and IgA autoantibodies against L1 p40, and this protein can be detected in circulating granulocytes in both pediatric and adult SLE patients. P40 expression and autoantibody levels correlate with disease activity. Markers of neutrophil activation and death also correlate with these autoantibodies and with disease activity, suggesting that neutrophils express L1 and are a source of p40.

Implications of Endogenous Retroelements in the Etiopathogenesis of Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease. While its etiology remains elusive, current understanding suggests a multifactorial process with contributions by genetic, immunologic, hormonal, and environmental factors. A hypothesis that combines several of these factors proposes that genomic elements, the L1 retrotransposons, are instrumental in SLE pathogenesis. L1 retroelements are transcriptionally activated in SLE and produce two proteins, ORF1p and ORF2p, which are immunogenic and can drive type I interferon (IFN) production by producing DNA species that activate cytosolic DNA sensors. In addition, these two proteins reside in RNA-rich macromolecular assemblies that also contain well-known SLE autoantigens like Ro60. We surmise that cells expressing L1 will exhibit all the hallmarks of cells infected by a virus, resulting in a cellular and humoral immune response similar to those in chronic viral infections. However, unlike exogenous viruses, L1 retroelements cannot be eliminated from the host genome. Hence, dysregulated L1 will cause a chronic, but perhaps episodic, challenge for the immune system. The clinical and immunological features of SLE can be at least partly explained by this model. Here we review the support for, and the gaps in, this hypothesis of SLE and its potential for new diagnostic, prognostic, and therapeutic options in SLE.

Acute skin exposure to ultraviolet light triggers neutrophil-mediated kidney inflammation.

Photosensitivity to ultraviolet (UV) light affects up to ∼80% of lupus patients. Sunlight exposure can exacerbate local as well as systemic manifestations of lupus, including nephritis, by mechanisms that are poorly understood. Here, we report that acute skin exposure to UV light triggers a neutrophil-dependent injury response in the kidney characterized by upregulated expression of endothelial adhesion molecules as well as inflammatory and injury markers associated with transient proteinuria. We showed that UV light stimulates neutrophil migration not only to the skin but also to the kidney in an IL-17A-dependent manner. Using a photoactivatable lineage tracing approach, we observed that a subset of neutrophils found in the kidney had transited through UV light-exposed skin, suggesting reverse transmigration. Besides being required for the renal induction of genes encoding mediators of inflammation (vcam-1, s100A9, and Il-1b) and injury (lipocalin-2 and kim-1), neutrophils significantly contributed to the kidney type I interferon signature triggered by UV light. Together, these findings demonstrate that neutrophils mediate subclinical renal inflammation and injury following skin exposure to UV light. Of interest, patients with lupus have subpopulations of blood neutrophils and low-density granulocytes with similar phenotypes to reverse transmigrating neutrophils observed in the mice post-UV exposure, suggesting that these cells could have transmigrated from inflamed tissue, such as the skin.

How Retroviruses and Retrotransposons in Our Genome May Contribute to Autoimmunity in Rheumatological Conditions.

More than 200 human disorders include various manifestations of autoimmunity. The molecular events that lead to these diseases are still incompletely understood and their causes remain largely unknown. Numerous potential triggers of autoimmunity have been proposed over the years, but very few of them have been conclusively confirmed or firmly refuted. Viruses have topped the lists of suspects for decades, and it seems that many viruses, including those of the Herpesviridae family, indeed can influence disease initiation and/or promote exacerbations by a number of mechanisms that include prolonged anti-viral immunity, immune subverting factors, and mechanisms, and perhaps "molecular mimicry". However, no specific virus has yet been established as being truly causative. Here, we discuss a different, but perhaps mechanistically related possibility, namely that retrotransposons or retroviruses that infected us in the past and left a lasting copy of themselves in our genome still can provoke an escalating immune response that leads to autoimmune disease. Many of these loci still encode for retroviral proteins that have retained some, or all, of their original functions. Importantly, these endogenous proviruses cannot be eliminated by the immune system the way it can eliminate exogenous viruses. Hence, if not properly controlled, they may drive a frustrated and escalating chronic, or episodic, immune response to the point of a frank autoimmune disorder. Here, we discuss the evidence and the proposed mechanisms, and assess the therapeutic options that emerge from the current understanding of this field.

Distal lung epithelial progenitor cell function declines with age.

Tissue stem cell exhaustion is a key hallmark of aging, and in this study, we characterised its manifestation in the distal lung. We compared the lungs of 3- and 22-month old mice. We examined the gross morphological changes in these lungs, the density and function of epithelial progenitor populations and the epithelial gene expression profile. Bronchioles became smaller in their cross-sectional area and diameter. Using long-term EdU incorporation analysis and immunohistochemistry, we found that bronchiolar cell density remained stable with aging, but inferred rates of bronchiolar club progenitor cell self-renewal and differentiation were reduced, indicative of an overall slowdown in cellular turnover. Alveolar Type II progenitor cell density and self-renewal were maintained per unit tissue area with aging, but rates of inferred differentiation into Type I cells, and indeed overall density of Type I cells was reduced. Microarray analysis revealed age-related changes in multiple genes, including some with roles in proliferation and differentiation, and in IGF and TGFß signalling pathways. By characterising how lung stem cell dynamics change with aging, this study will elucidate how they contribute to age-related loss of pulmonary function, and pathogenesis of common age-related pulmonary diseases.

Role of Neutrophils in Systemic Vasculitides.

Neutrophils and neutrophil extracellular traps (NETs) contribute to the pathogenesis of many autoimmune diseases, including vasculitis. Though neutrophils, and NETs, can break self-tolerance by being a source of autoantigens for autoantibodies in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, playing a key role in driving the autoimmune response, the role of neutrophils and NETs in large vessel vasculitis, including giant cell arteritis (GCA), is not well understood. In this review, we summarize the current insight into molecular mechanisms contributing to neutrophil-mediated pathology in small and medium vessel vasculitis, as well as provide potential translational perspectives on how neutrophils, and NETs, may partake in large vessel vasculitis, a rare disease entity of unclear pathogenesis.