IL-21 Promotes Pulmonary Fibrosis through the Induction of Profibrotic CD8+ T Cells

TGF-β signaling: critical nexus of fibrogenesis and cancer

The transforming growth factor-beta (TGF-β) signaling pathway is a vital regulator of cell proliferation, differentiation, apoptosis, and extracellular matrix production. It functions through canonical SMAD-mediated processes and noncanonical pathways involving MAPK cascades, PI3K/AKT, Rho-like GTPases, and NF-κB signaling. This intricate signaling system is finely tuned by interactions between canonical and noncanonical pathways and plays key roles in both physiologic and pathologic conditions including tissue homeostasis, fibrosis, and cancer progression. TGF-β signaling is known to have paradoxical actions. Under normal physiologic conditions, TGF-β signaling promotes cell quiescence and apoptosis, acting as a tumor suppressor. In contrast, in pathological states such as inflammation and cancer, it triggers processes that facilitate cancer progression and tissue remodeling, thus promoting tumor development and fibrosis. Here, we detail the role that TGF-β plays in cancer and fibrosis and highlight the potential for future theranostics targeting this pathway.

Murine MHC-Deficient Nonobese Diabetic Mice Carrying Human HLA-DQ8 Develop Severe Myocarditis and Myositis in Response to Anti-PD-1 Immune Checkpoint Inhibitor Cancer Therapy

Myocarditis has emerged as an immune-related adverse event of immune checkpoint inhibitor (ICI) cancer therapy associated with significant mortality. To ensure patients continue to safely benefit from life-saving cancer therapy, an understanding of fundamental immunological phenomena underlying ICI myocarditis is essential. We recently developed the NOD-cMHCI/II-/-.DQ8 mouse model that spontaneously develops myocarditis with lower mortality than observed in previous HLA-DQ8 NOD mouse strains. Our strain was rendered murine MHC class I and II deficient using CRISPR/Cas9 technology, making it a genetically clean platform for dissecting CD4+ T cell-mediated myocarditis in the absence of classically selected CD8+ T cells. These mice are highly susceptible to myocarditis and acute heart failure following anti-PD-1 ICI-induced treatment. Additionally, anti-PD-1 administration accelerates skeletal muscle myositis. Using histology, flow cytometry, adoptive transfers, and RNA sequencing analyses, we performed a thorough characterization of cardiac and skeletal muscle T cells, identifying shared and unique characteristics of both populations. Taken together, this report details a mouse model with features of a rare, but highly lethal clinical presentation of overlapping myocarditis and myositis following ICI therapy. This study sheds light on underlying immunological mechanisms in ICI myocarditis and provides the basis for further detailed analyses of diagnostic and therapeutic strategies.

A prognostic model of idiopathic pulmonary fibrosis constructed based on macrophage and mitochondria-related genes

BACKGROUND

Studies have shown that mitochondrial function and macrophages may play a role in the development of idiopathic pulmonary fibrosis (IPF). However, the understanding of the interactions and specific mechanisms between mitochondrial function and macrophages in pulmonary fibrosis is still very limited.

METHODS

To construct a prognostic model for IPF based on Macrophage- related genes (MaRGs) and Mitochondria-related genes (MitoRGs), differential analysis was performed to achieve differentially expressed genes (DEGs) between IPF and Control groups in the GSE28042 dataset. Then, MitoRGs, MaRGs and DEGs were overlapped to screen out the signature genes. The univariate Cox analysis and the least absolute shrinkage and selection operator (LASSO) algorithm were implemented to achieve key genes. Furthermore, the independent prognostic analysis was employed. The ingenuity pathway analysis (IPA) was employed to further understand the molecular mechanisms of key genes.Next, the immune infiltration analysis was implemented to identify differential immune cells between two risk subgroups.

RESULTS

There were 4791 DEGs between IPF and Control groups. Furthermore, 26 signature genes were achieved by the intersection processing. Three key genes including ALDH2, MCL1, and BCL2A1 were achieved, and the risk model based on the key genes was created. In addition, a nomogram for survival forecasting of IPF patients was created based on riskScore, Age, and Gender, and we found that key genes were associated with classical pathways including 'Apoptosis Signaling', 'PI3K/AKT Signaling', and so on. Next, two differential immune cells including Monocytes and CD8 T cells were identified between two risk subgroups. Moreover, we found that MIR29B2CHG and hsa-mir-1-3p could regulate the expression of ALDH2.

CONCLUSION

We achieved 3 key genes including ALDH2, MCL1,, and BCL2A1 associated with IPF, providing a new theoretical basis for clinical treatment of IPF.

The clinical manifestations and molecular pathogenesis of radiation fibrosis

Advances in radiation techniques have enabled the precise delivery of higher doses of radiotherapy to tumours, while sparing surrounding healthy tissues. Consequently, the incidence of radiation toxicities has declined, and will likely continue to improve as radiotherapy further evolves. Nonetheless, ionizing radiation elicits tissue-specific toxicities that gradually develop into radiation-induced fibrosis, a common long-term side-effect of radiotherapy. Radiation fibrosis is characterized by an aberrant wound repair process, which promotes the deposition of extensive scar tissue, clinically manifesting as a loss of elasticity, tissue thickening, and organ-specific functional consequences. In addition to improving the existing technologies and guidelines directing the administration of radiotherapy, understanding the pathogenesis underlying radiation fibrosis is essential for the success of cancer treatments. This review integrates the principles for radiotherapy dosimetry to minimize off-target effects, the tissue-specific clinical manifestations, the key cellular and molecular drivers of radiation fibrosis, and emerging therapeutic opportunities for both prevention and treatment.

IL-21, not IL-17A, exacerbates murine primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease caused by intrahepatic bile duct injuries, resulting in fibrosis, cirrhosis, and eventually liver failure. T helper (Th) 17 cells are proposed to involve in the pathogenesis of PBC. However, how and which Th17 cell-derived cytokines affect PBC remains unclear. In this study, we investigated the effects of Th17 effector cytokines, including interleukin (IL)-17A, IL-17F, and IL-21 in PBC using a xenobiotic-induced mouse model of autoimmune cholangitis (inducible chemical xenobiotic models of PBC) treated with cytokine-expressing adeno-associated virus. Our results showed that administration of IL-17A, the well-known main cytokine produced by Th17 cells, did not augment liver inflammation or fibrosis. In contrast, we noted IL-17A-treated mice had lower hepatic Th1 cell numbers and higher hepatic CD11b+Ly6G+ polymorphonuclear myeloid-derived suppressor cell numbers. IL-17F did not alter liver inflammation or fibrosis. However, the administration of IL-21 exacerbated liver inflammatory responses and portal cell infiltration. IL-21 markedly increased the numbers of activated CD8+ T cells and liver tissue-resident memory CD8+ T cells. Moreover, IL-21 aggravates liver fibrosis in mice with autoimmune cholangitis. These results emphasized that not IL-17A but IL-21 in Th17 cell-derived cytokines affected the pathogenesis of PBC. IL-21 enhanced liver inflammation and progression to fibrosis by enhancing the numbers and effector activities of CD8+ T cells. Delineation of the effects of different Th17 effector cytokines in PBC offers clues for developing new therapeutic approaches.

The effector program of human CD8 T cells supports tissue remodeling

CD8 T lymphocytes are classically viewed as cytotoxic T cells. Whether human CD8 T cells can, in parallel, induce a tissue regeneration program is poorly understood. Here, antigen-specific assay systems revealed that human CD8 T cells not only mediated cytotoxicity but also promoted tissue remodeling. Activated CD8 T cells could produce the epidermal growth factor receptor (EGFR)-ligand amphiregulin (AREG) and sensitize epithelial cells for enhanced regeneration potential. Blocking the EGFR or the effector cytokines IFN-γ and TNF could inhibit tissue remodeling. This regenerative program enhanced tumor spheroid and stem cell-mediated organoid growth. Using single-cell gene expression analysis, we identified an AREG+, tissue-resident CD8 T cell population in skin and adipose tissue from patients undergoing abdominal wall or abdominoplasty surgery. These tissue-resident CD8 T cells showed a strong TCR clonal relation to blood PD1+TIGIT+ CD8 T cells with tissue remodeling abilities. These findings may help to understand the complex CD8 biology in tumors and could become relevant for the design of therapeutic T cell products.

APPLICATION OF QUANTILE DISCRETIZATION AND BAYESIAN NETWORK ANALYSIS TO PUBLICLY AVAILABLE CYSTIC FIBROSIS DATA SETS

The availability of multiple publicly-available datasets studying the same phenomenon has the promise of accelerating scientific discovery. Meta-analysis can address issues of reproducibility and often increase power. The promise of meta-analysis is especially germane to rarer diseases like cystic fibrosis (CF), which affects roughly 100,000 people worldwide. A recent search of the National Institute of Health's Gene Expression Omnibus revealed 1.3 million data sets related to cancer compared to about 2,000 related to CF. These studies are highly diverse, involving different tissues, animal models, treatments, and clinical covariates. In our search for gene expression studies of primary human airway epithelial cells, we identified three studies with compatible methodologies and sufficient metadata: GSE139078, Sala Study, and PRJEB9292. Even so, experimental designs were not identical, and we identified significant batch effects that would have complicated functional analysis. Here we present quantile discretization and Bayesian network construction using the Hill climb method as a powerful tool to overcome experimental differences and reveal biologically relevant responses to the CF genotype itself, exposure to virus, bacteria, and drugs used to treat CF. Functional patterns revealed by cluster Profiler included interferon signaling, interferon gamma signaling, interleukins 4 and 13 signaling, interleukin 6 signaling, interleukin 21 signaling, and inactivation of CSF3/G-CSF signaling pathways showing significant alterations. These pathways were consistently associated with higher gene expression in CF epithelial cells compared to non-CF cells, suggesting that targeting these pathways could improve clinical outcomes. The success of quantile discretization and Bayesian network analysis in the context of CF suggests that these approaches might be applicable to other contexts where exactly comparable data sets are hard to find.

Mechanisms and management of cough in interstitial lung disease

INTRODUCTION

Many patients with interstitial lung diseases (ILDs), especially fibrotic ILDs, experience chronic cough. It negatively impacts both physical and psychological well-being. Effective treatment options are limited.

AREAS COVERED

The pathophysiology of chronic cough in IPF is complex and involves multiple mechanisms, including mechanical distortion of airways, parenchyma, and nerve fibers. The pathophysiology of cough in other fibrosing ILDs is poorly understood and involves various pathways. The purpose of this review is to highlight mechanisms of chronic cough and to present therapeutic evidence for its management in the most commonly occurring diffuse fibrosing lung diseases including idiopathic pulmonary fibrosis (IPF), connective tissue disease-related interstitial lung disease (CTD-ILD), sarcoidosis-related ILD (Sc-ILD), chronic hypersensitivity pneumonitis-related ILD (CHP-ILD), and post-COVID-19-related interstitial lung disease (PC-ILD).

EXPERT OPINION

This review guides the management of chronic cough in fibrosing ILDs. In this era of precision medicine, chronic cough management should be individualized in each interstitial lung disease.

The Role of Immune Cells in the Pathogenesis of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease of unknown etiology with limited treatment options. The role of the immune system in IPF has received increasing attention. Uncontrolled immune responses drive the onset and progression of IPF. This article provides an overview of the role of innate immune cells (including macrophages, neutrophils, mast cells, eosinophils, dendritic cells, nature killer cells, nature kill cells and γδ T cells) and adaptive immune cells (including Th1 cells, Th2 cells, Th9 cells, Th17 cells, Th22 cells, cytotoxic T cells, B lymphocytes and Treg cells) in IPF. In addition, we review the current status of pharmacological treatments for IPF and new developments in immunotherapy. A deeper comprehension of the immune system's function in IPF may contribute to the development of targeted immunomodulatory therapies that can alter the course of the disease.

PTX3 shapes profibrotic immune cells and epithelial/fibroblast repair and regeneration in a murine model of pulmonary fibrosis

The long pentraxin 3 (PTX3) is protective in different pathologies but was not analyzed in-depth in Idiopathic Pulmonary Fibrosis (IPF). Here, we have explored the influence of PTX3 in the bleomycin (BLM)-induced murine model of IPF by looking at immune cells (macrophages, mast cells, T cells) and stemness/regenerative markers of lung epithelium (SOX2) and fibro-blasts/myofibroblasts (CD44) at different time points that retrace the progression of the disease from onset at day 14, to full-blown disease at day 21, to incomplete regression at day 28. We took advantage of transgenic PTX3 overexpressing mice (Tie2-PTX3) and Ptx3 null ones (PTX3-KO) in which pulmonary fibrosis was induced. Our data have shown that PTX3 overexpression in Tie2-PTX3 compared to WT or PTX3-KO: reduced CD68+ and CD163+ macrophages and the Tryptase+ mast cells during the whole experimental time; on the contrary, CD4+ T cells are consistently present on day 14 and dramatically decreased on day 21; CD8+ T cells do not show significant differences on day 14, but are significantly reduced on day 21; SOX2 is reduced on days 14 and 21; CD44 is reduced on day 21. Therefore, PTX3 could act on the proimmune and fibrogenic microenvironment to prevent fibrosis in BLM-treated mice.

T Follicular Helper Cells in Tertiary Lymphoid Structure Contribute to Renal Fibrosis by IL-21

Tertiary lymphoid structure (TLS) represents lymphocyte clusters in non-lymphoid organs. The formation and maintenance of TLS are dependent on follicular helper T (TFH) cells. However, the role of TFH cells during renal TLS formation and the renal fibrotic process has not been comprehensively elucidated in chronic kidney disease. Here, we detected the circulating TFH cells from 57 IgAN patients and found that the frequency of TFH cells was increased in IgA nephropathy patients with renal TLS and also increased in renal tissues from the ischemic-reperfusion-injury (IRI)-induced TLS model. The inducible T-cell co-stimulator (ICOS) is one of the surface marker molecules of TFH. Remarkably, the application of an ICOS-neutralizing antibody effectively prevented the upregulation of TFH cells and expression of its canonical functional mediator IL-21, and also reduced renal TLS formation and renal fibrosis in IRI mice in vivo. In the study of this mechanism, we found that recombinant IL-21 could directly promote renal fibrosis and the expression of p65. Furthermore, BAY 11-7085, a p65 selective inhibitor, could effectively alleviate the profibrotic effect induced by IL-21 stimulation. Our results together suggested that TFH cells contribute to TLS formation and renal fibrosis by IL-21. Targeting the ICOS-signaling pathway network could reduce TFH cell infiltration and alleviate renal fibrosis.

Tissue-resident memory T cells and lung immunopathology

Rapid reaction to microbes invading mucosal tissues is key to protect the host against disease. Respiratory tissue-resident memory T (TRM ) cells provide superior immunity against pathogen infection and/or re-infection, due to their presence at the site of pathogen entry. However, there has been emerging evidence that exuberant TRM -cell responses contribute to the development of various chronic respiratory conditions including pulmonary sequelae post-acute viral infections. In this review, we have described the characteristics of respiratory TRM cells and processes underlying their development and maintenance. We have reviewed TRM -cell protective functions against various respiratory pathogens as well as their pathological activities in chronic lung conditions including post-viral pulmonary sequelae. Furthermore, we have discussed potential mechanisms regulating the pathological activity of TRM cells and proposed therapeutic strategies to alleviate TRM -cell-mediated lung immunopathology. We hope that this review provides insights toward the development of future vaccines or interventions that can harness the superior protective abilities of TRM cells, while minimizing the potential for immunopathology, a particularly important topic in the era of coronavirus disease 2019 (COVID-19) pandemic.

Diagnostic and prognostic biomarkers for progressive fibrosing interstitial lung disease

No biomarkers have been identified in bronchoalveolar lavage fluid (BALF) for predicting fibrosis progression or prognosis in progressive fibrosing interstitial lung disease (PF-ILD). We investigated BALF biomarkers for PF-ILD diagnosis and prognosis assessment. Overall, 120 patients with interstitial pneumonia who could be diagnosed with PF-ILD or non PF-ILD were enrolled in this retrospective study. PF-ILD was diagnosed according to Cottin's definition. All patients underwent bronchoscopy and BALF collection. We evaluated blood and BALF parameters, high-resolution computed tomography (HRCT) patterns, and spirometry data to identify factors influencing PF-ILD diagnosis and prognosis. On univariate logistic analysis, age, sex, the BALF white blood cell fraction (neutrophil, lymphocyte, eosinophil, and neutrophil-to-lymphocyte ratio), BALF flow cytometric analysis (CD8), and an idiopathic pulmonary fibrosis/usual interstitial pneumonia pattern on HRCT were correlated with PF-ILD diagnosis. Multivariate logistic regression analysis revealed that sex (male), age (cut-off 62 years, area under the curve [AUC] 0.67; sensitivity 0.80; specificity 0.47), white blood cell fraction in BALF (NLR, neutrophil, and lymphocyte), and CD8 in BALF (cut-off 34.2; AUC 0.66; sensitivity, 0.74; specificity, 0.62) were independent diagnostic predictors for PF-ILD. In BALF, the NLR (cut-off 8.70, AUC 0.62; sensitivity 0.62; specificity 0.70), neutrophil count (cut-off 3.0, AUC 0.59; sensitivity 0.57; specificity 0.63), and lymphocyte count (cut-off 42.0, AUC 0.63; sensitivity 0.77; specificity 0.53) were independent diagnostic predictors. In PF-ILD patients (n = 77), lactate dehydrogenase (cut-off 275, AUC 0.69; sensitivity 0.57; specificity 0.78), Krebs von den Lungen-6 (cut-off 1,140, AUC 0.74; sensitivity 0.71; specificity 0.76), baseline forced vital capacity (FVC) (cut-off 1.75 L, AUC 0.71; sensitivity, 0.93; specificity, 0.46), and BALF neutrophil ratio (cut-off 6.0, AUC 0.72; sensitivity 0.79; specificity 0.80) correlated with death within 3 years. The BALF cellular ratio, particularly the neutrophil ratio, correlated with the diagnosis and prognosis of PF-ILD. These findings may be useful in the management of patients with interstitial pneumonia.

Chlamydia transmitting from the genital to gastrointestinal tract and inducing tubal disease: Double attack pattern

Chlamydia trachomatis ( CT ) genital tract infection is insidious, and patients often have no conscious symptoms.Delayed treatment after infection can lead to serious complications. Chlamydia muridarum ( CM ) genital tract infection in female mice can simulate CT genital tract infection in women, which is an ideal model to investigate the pathogenesis of CT . CM plasmid protein pGP3, chromosomal protein TC0237/TC0668, CM -specific CD8 + T cells, TNF-α, and IL-13 can induce genital tract inflammation, CD4 + T cells are responsible for CM clearance. However, tubal inflammation persists after genital tract CM is removed. Genital tract CM can spread spontaneously in vivo and colonize the gastrointestinal (GI) tract, but the GI tract CM cannot reverse spread to the genital tract. The survival time and number of CM transmitted from genital tract to GI tract are positively correlated with the long-term lesion of oviduct, while the CM inoculated directly into the GI tract has no pathogenicity in both the genital and GI tract. The double attack pattern of Chlamydia -induced genital tract inflammatory lesions is as follows: CM infection of oviduct epithelial cells initiates the process of oviduct repair as the first attack. After genital CM spreads to the GI tract, activated chlamydia-specific CD8 + T cells are recruited to the genital tract and secreted pro-fibrotic cytokines such as TNF-α and IL-13. This process is called the second attack which transform tubal repair initiated by the first attack into long-term tubal fibrosis/hydrosalpinx. Elucidating the pathogenic mechanism of Chlamydia infection can provide new ideas for the development of Chlamydia vaccine, which is expected to solve the problems of infertility caused by repeated CT infection in women.

The role of immune response in the pathogenesis of idiopathic pulmonary fibrosis: far beyond the Th1/Th2 imbalance

INTRODUCTION

. Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unknown origin characterized by progressive scarring of the lung leading to irreversible loss of function. Despite the availability of two drugs that are able to slow down disease progression, IPF remains a deadly disease. The pathogenesis of IPF is poorly understood, but a dysregulated wound healing response following recurrent alveolar epithelial injury is thought to be crucial. Areas covered. In the last few years, the role of the immune system in IPF pathobiology has been reconsidered; indeed, recent data suggest that a dysfunctional immune system may promote and unfavorable interplay with pro-fibrotic pathways thus acting as a cofactor in disease development and progression. In this article, we review and critically discuss the role of T cells in the pathogenesis and progression of IPF in the attempt to highlight ways in which further research in this area may enable the development of targeted immunomodulatory therapies for this dreadful disease.

EXPERT OPINION

A better understanding of T cells interactions has the potential to facilitate the development of immune modulators targeting multiple T cell-mediated pathways thus halting disease initiation and progression.

Intestinal Fibrosis in Inflammatory Bowel Disease and the Prospects of Mesenchymal Stem Cell Therapy

Intestinal fibrosis is an important complication of inflammatory bowel disease (IBD). In the course of the development of fibrosis, certain parts of the intestine become narrowed, significantly destroying the structure and function of the intestine and affecting the quality of life of patients. Chronic inflammation is an important initiating factor of fibrosis. Unfortunately, the existing anti-inflammatory drugs cannot effectively prevent and alleviate fibrosis, and there is no effective anti-fibrotic drug, which makes surgical treatment the mainstream treatment for intestinal fibrosis and stenosis. Mesenchymal stem cells (MSCs) are capable of tissue regeneration and repair through their self-differentiation, secretion of cytokines, and secretion of extracellular vesicles. MSCs have been shown to play an important therapeutic role in the fibrosis of many organs. However, the role of MSC in intestinal fibrosis largely remained unexplored. This review summarizes the mechanism of intestinal fibrosis, including the role of immune cells, TGF-β, and the gut microbiome and metabolites. Available treatment options for fibrosis, particularly, MSCs are also discussed.

Dermatomyositis With Anti-MDA5 Antibodies: Bioclinical Features, Pathogenesis and Emerging Therapies

Anti-MDA5 dermatomyositis is a rare systemic autoimmune disease, historically described in Japanese patients with clinically amyopathic dermatomyositis and life-threatening rapidly progressive interstitial lung disease. Subsequently, the complete clinical spectrum of the disease was enriched by skin, articular and vascular manifestations. Depending on the predominance of these symptoms, three distinct clinical phenotypes with different prognosis are now defined. To date, the only known molecular component shared by the three entities are specific antibodies targeting MDA5, a cytosolic protein essential for antiviral host immune responses. Several biological tools have emerged to detect these antibodies, with drawbacks and limitations for each of them. However, the identification of this highly specific serological marker of the disease raises the question of its role in the pathogenesis. Although current knowledge on the pathogenic mechanisms that take place in the disease are still in their enfancy, several lines of evidence support a central role of interferon-mediated vasculopathy in the development of skin and lung lesions, as well as a possible pathogenic involvement of anti-MDA5 antibodies. Here, we review the clinical and biological evidences in favor of these hypothesis, and we discuss the contribution of emerging therapies that shed some light on the pathogenesis of the disease.

Differences in epithelial-mesenchymal-transition in paraquat-induced pulmonary fibrosis in BALB/C and BALB/C (nu/nu) nude mice

Exposure to the toxic herbicide paraquat (PQ) can lead to the active absorption and enrichment of alveolar epithelial cells, resulting in pulmonary fibrosis and respiratory failure. At present, no effective clinical treatment is available. Notably, however, patients infected with human acquired immunodeficiency virus (HIV) (with T lymphocyte deficiency) do not show pulmonary fibrosis after PQ poisoning, suggesting that T lymphocytes may be involved in the occurrence and pathological development of lung fibers following PQ exposure, although relevant studies remain limited. Here, we found that the degree of pulmonary fibrosis induced by intragastric administration of PQ in congenital immunodeficiency BALB/C (nu/nu) nude (T lymphocyte loss) mice was lower than that in normal mice. However, pulmonary fibrosis was aggravated after transplantation of BALB/C (nu/nu) T lymphocytes into congenital immunodeficiency mice. This study is the first to report on the involvement of T lymphocytes in the occurrence and pathological development of lung fibers induced by PQ exposure. Thus, T cells may be an important cellular target for the clinical treatment of pulmonary fibrosis caused by PQ.

Characterization of pathogenic CD8+ T cells in Chlamydia-infected OT1 mice

Chlamydia trachomatis is a leading infectious cause of infertility in women due to its induction of lasting pathology such as hydrosalpinx. Chlamydia muridarum induces mouse hydrosalpinx because C. muridarum can both invade tubal epithelia directly (as a 1^st hit) and induce lymphocytes to promote hydrosalpinx indirectly (as a 2^nd hit). In the current study, a critical role of CD8⁺ T cells in chlamydial induction of hydrosalpinx was validated in both wild type C57BL/6J and OT1 transgenic mice. OT1 mice failed to develop hydrosalpinx partially due to the failure of their lymphocytes to recognize chlamydial antigens. CD8⁺ T cells from naïve C57BL/6J rescued the recipient OT1 mice to develop hydrosalpinx when naïve CD8⁺ T cells were transferred at the time of infection with Chlamydia. However, when the transfer was delayed for 2 weeks or longer after the chlamydial infection, naïve CD8⁺ T cells no longer promoted hydrosalpinx. Nevertheless, Chlamydia-immunized CD8⁺ T cells still promoted significant hydrosalpinx in the recipient OT1 mice even when the transfer was delayed for 3 weeks. Thus, CD8⁺ T cells must be primed within 2 weeks after chlamydial infection to be pathogenic but once primed, they can promote hydrosalpinx for >3 weeks. However, Chlamydia-primed CD4⁺ T cells failed to promote chlamydial induction of pathology in OT1 mice. This study has optimized an OT1 mouse-based model for revealing the pathogenic mechanisms of Chlamydia-specific CD8⁺ T cells.

Bleomycin-Induced Lung Injury Increases Resistance to Influenza Virus Infection in a Type I Interferon-Dependent Manner

Acute lung injury (ALI) results in acute respiratory disease that causes fatal respiratory diseases; however, little is known about the incidence of influenza infection in ALI. Using a ALI-mouse model, we investigated the pro-inflammatory cytokine response to ALI and influenza infection. Mice treated with bleomycin (BLM), which induces ALI, were more resistant to influenza virus infection and exhibited higher levels of type I interferon (IFN-I) transcription during the early infection period than that in PBS-treated control mice. BLM-treated mice also exhibited a lower viral burden, reduced pro-inflammatory cytokine production, and neutrophil levels. In contrast, BLM-treated IFN-I receptor 1 (IFNAR1)-knockout mice failed to show this attenuated phenotype, indicating that IFN-I is key to the antiviral response in ALI-induced mice. The STING/TBK1/IRF3 pathway was found to be involved in IFN-I production and the establishment of an antiviral environment in the lung. The depletion of plasmacytoid dendritic cells (pDCs) reduced the effect of BLM treatment against influenza virus infection, suggesting that pDCs are the major source of IFN-I and are crucial for defense against viral infection in BLM-induced lung injury. Overall, this study showed that BLM-mediated ALI in mice induced the release of double-stranded DNA, which in turn potentiated IFN-I-dependent pulmonary viral resistance by activating the STING/TBK1/IRF3 pathway in association with pDCs.

Gastrointestinal Chlamydia-induced CD8+ T cells promote chlamydial pathogenicity in the female upper genital tract

Chlamydia is known to both ascend to the upper genital tract and spread to the gastrointestinal tract following intravaginal inoculation. The gastrointestinal Chlamydia was recently reported to promote chlamydial pathogenicity in the genital tract since mice intravaginally inoculated with an attenuated Chlamydia, which alone failed to develop pathology in the genital tract, were restored to develop hydrosalpinx by intragastric co-inoculation with wild type Chlamydia. Gastrointestinal Chlamydia promoted hydrosalpinx via an indirect mechanism since Chlamydia in the gut did not directly spread to the genital tract lumen. In the current study, we further investigated the role of CD8⁺ T cells in the promotion of hydrosalpinx by gastrointestinal Chlamydia. First, we confirmed that intragastric co-inoculation with wild type Chlamydia promoted hydrosalpinx in mice that were inoculated with an attenuated Chlamydia in the genital tract one week earlier. Second, the promotion of hydrosalpinx by intragastrically co-inoculated Chlamydia was blocked by depleting CD8⁺ T cells. Third, adoptive transfer of the gastrointestinal Chlamydia-induced CD8⁺ T cells was sufficient for promoting hydrosalpinx in mice that were intravaginally inoculated with an attenuated Chlamydia. These observations have demonstrated that CD8⁺ T cells induced by gastrointestinal Chlamydia are both necessary and sufficient for promoting hydrosalpinx in the genital tract. The study has laid a foundation for further revealing the mechanisms by which Chlamydia-induced T lymphocyte responses (as a 2^nd hit) promote hydrosalpinx in mice with genital Chlamydia-triggered tubal injury (as a 1^st hit), a continuing effort in testing the two-hit hypothesis as a chlamydial pathogenic mechanism.

The Role of CX3CL1 and ADAM17 in Pathogenesis of Diffuse Parenchymal Lung Diseases

Fractalkine (CX3CL1) is a unique chemokine that functions as a chemoattractant for effector cytotoxic lymphocytes and macrophages expressing fractalkine receptor CX3CR1. CX3CL1 exists in two forms—a soluble and a membrane-bound form. The soluble CX3CL1 is released from cell membranes by proteolysis by the TNF-α-converting enzyme/disintegrin-like metalloproteinase 17 (TACE/ADAM17) and ADAM10. In this study, we evaluated the diagnostic relevance and potential roles of CX3CL1 and ADAM17 in the pathogenesis of diffuse parenchymal lung diseases (DPLDs) in the human population. The concentration of CX3CL1 and ADAM17 was measured by the enzyme-linked immunosorbent assay (ELISA) test in bronchoalveolar lavage fluids of patients suffering from different DPLDs. The concentration of CX3CL1 was significantly higher in patients suffering from idiopathic pulmonary fibrosis (IPF) and hypersensitivity pneumonitis patients compared to the control group. A significantly higher concentration of CX3CL1 was measured in fibrotic DPLDs compared to non-fibrotic DLPD patients. We found a positive correlation of CX3CL1 levels with the number of CD8+ T cells, and a negative correlation with CD4+ T cells in BALF and diffusion capacity for carbon monoxide. The concentration of ADAM17 was significantly lower in the IPF group compared to the other DPLD groups. We noticed a significantly higher CX3CL1/ADAM17 ratio in the IPF group compared to the other DPLD groups. We suggest that CX3CL1 has a distinctive role in the pathogenesis of DPLDs. The level of CX3CL1 strongly correlates with the severity of lung parenchyma impairment. The results suggest that high values of CX3CL1/ADAM17 could be diagnostic markers for IPF.

Conventional Type 1 Dendritic Cells (cDC1) in Human Kidney Diseases: Clinico-Pathological Correlations

Background

cDC1 is a subset of conventional DCs, whose most recognized function is cross-presentation to CD8⁺ T cells. We conducted this study to investigate the number and location of cDC1s in various human kidney diseases as well as their correlation with clinico-pathological features and CD8⁺ T cells.

Methods

We analyzed 135 kidney biopsies samples. Kidney diseases included: acute tubular necrosis (ATN), acute interstitial nephritis (AIN), proliferative glomerulonephritis (GN) (IgA nephropathy, lupus nephritis, pauci-immune GN, anti-GBM disease), non-proliferative GN (minimal change disease, membranous nephropathy) and diabetic nephropathy. Indirect immunofluorescence staining was used to quantify cDC1s, CD1c⁺ DCs, and CD8⁺ T cells.

Results

cDC1s were rarely present in normal kidneys. Their number increased significantly in ATN and proliferative GN, proportionally much more than CD1c⁺ DCs. cDC1s were mainly found in the interstitium, except in lupus nephritis, pauci-immune GN and anti-GBM disease, where they were prominent in glomeruli and peri-glomerular regions. The number of cDC1s correlated with disease severity in ATN, number of crescents in pauci-immune GN, interstitial fibrosis in IgA nephropathy and lupus nephritis, as well as prognosis in IgA nephropathy. The number of CD8⁺ T cells also increased significantly in these conditions and cDC1 number correlated with CD8⁺ T cell number in lupus nephritis and pauci-immune GN, with many of them closely co-localized.

Conclusions

cDC1 number correlated with various clinic-pathological features and prognosis reflecting a possible role in these conditions. Their association with CD8⁺ T cells suggests a combined mechanism in keeping with the results in animal models.

Immune dysregulation as a driver of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) affects hundreds of thousands of people worldwide, reducing their quality of life and leading to death from respiratory failure within years of diagnosis. Treatment options remain limited, with only two FDA-approved drugs available in the United States, neither of which reverse the lung damage caused by the disease or prolong the life of individuals with IPF. The only cure for IPF is lung transplantation. In this review, we discuss recent major advances in our understanding of the role of the immune system in IPF that have revealed immune dysregulation as a critical driver of disease pathophysiology. We also highlight ways in which an improved understanding of the immune system's role in IPF may enable the development of targeted immunomodulatory therapies that successfully halt or potentially even reverse lung fibrosis.

Pulmonary restriction predicts long-term pulmonary impairment in people with HIV and tuberculosis

Background

While tuberculosis is considered a risk factor for chronic obstructive pulmonary disease, a restrictive pattern of pulmonary impairment may actually be more common among tuberculosis survivors. We aimed to determine the nature of pulmonary impairment before and after treatment among people with HIV and tuberculosis and identify risk factors for long-term impairment.

Methods

In this prospective cohort study conducted in South Africa, we enrolled adults newly diagnosed with HIV and tuberculosis who were initiating antiretroviral therapy and tuberculosis treatment. We measured lung function and symptoms at baseline, 6, and 12 months. We compared participants with and without pulmonary impairment and constructed logistic regression models to identify characteristics associated with pulmonary impairment.

Results

Among 134 participants with a median CD4 count of 110 cells/μl, 112 (83%) completed baseline spirometry at which time 32 (29%) had restriction, 13 (12%) had obstruction, and 9 (7%) had a mixed pattern. Lung function was dynamic over time and 30 (33%) participants had impaired lung function at 12 months. Baseline restriction was associated with greater symptoms and with long-term pulmonary impairment (adjusted odds ratio 5.44, 95% confidence interval 1.16–25.45), while baseline obstruction was not (adjusted odds ratio 1.95, 95% confidence interval 0.28–13.78).

Conclusions

In this cohort of people with HIV and tuberculosis, restriction was the most common, symptomatic, and persistent pattern of pulmonary impairment. These data can help to raise awareness among clinicians about the heterogeneity of post-tuberculosis pulmonary impairment, and highlight the need for further research into mediators of lung injury in this vulnerable population.

The Roles of Immune Cells in the Pathogenesis of Fibrosis

Tissue injury and inflammatory response trigger the development of fibrosis in various diseases. It has been recognized that both innate and adaptive immune cells are important players with multifaceted functions in fibrogenesis. The activated immune cells produce various cytokines, modulate the differentiation and functions of myofibroblasts via diverse molecular mechanisms, and regulate fibrotic development. The immune cells exhibit differential functions during different stages of fibrotic diseases. In this review, we summarized recent advances in understanding the roles of immune cells in regulating fibrotic development and immune-based therapies in different disorders and discuss the underlying molecular mechanisms with a focus on mTOR and JAK-STAT signaling pathways.

T Cells in Fibrosis and Fibrotic Diseases

Fibrosis is the extensive deposition of fibrous connective tissue, and it is characterized by the accumulation of collagen and other extracellular matrix (ECM) components. Fibrosis is essential for wound healing and tissue repair in response to a variety of triggers, which include infection, inflammation, autoimmune disorder, degenerative disease, tumor, and injury. Fibrotic remodeling in various diseases, such as liver cirrhosis, pulmonary fibrosis, renal interstitial fibrosis, myocardial infarction, systemic sclerosis (SSc), and graft-versus-host disease (GVHD), can impair organ function, causing high morbidity and mortality. Both innate and adaptive immunity are involved in fibrogenesis. Although the roles of macrophages in fibrogenesis have been studied for many years, the underlying mechanisms concerning the manner in which T cells regulate fibrosis are not completely understood. The T cell receptor (TCR) engages the antigen and shapes the repertoire of antigen-specific T cells. Based on the divergent expression of surface molecules and cell functions, T cells are subdivided into natural killer T (NKT) cells, γδ T cells, CD8⁺ cytotoxic T lymphocytes (CTL), regulatory T (Treg) cells, T follicular regulatory (Tfr) cells, and T helper cells, including Th1, Th2, Th9, Th17, Th22, and T follicular helper (Tfh) cells. In this review, we summarize the pro-fibrotic or anti-fibrotic roles and distinct mechanisms of different T cell subsets. On reviewing the literature, we conclude that the T cell regulations are commonly disease-specific and tissue-specific. Finally, we provide perspectives on microbiota, viral infection, and metabolism, and discuss the current advancements of technologies for identifying novel targets and developing immunotherapies for intervention in fibrosis and fibrotic diseases.

TREM-1 and TREM-2 Expression on CD14+ Cells in Bronchoalveolar Lavage Fluid in Pulmonary Sarcoidosis and Hypersensitivity Pneumonitis in the Context of T Cell Immune Response

Background

Sarcoidosis and hypersensitivity pneumonitis (HP) are immunologically mediated processes caused by hypersensitivity reaction accompanied by similar features including lymphocytic alveolitis and granuloma formation. Recent studies describe the role of TREM receptors in T cell activation, differentiation, and granuloma formation. Alveolar macrophages activation via TREM receptors may be the key factor mediating subsequent immune response. The aim of the study was to analyse TREM-1 and TREM-2 expression to identify further molecular mechanisms participating in the immunopathogenesis of sarcoidosis and HP.

Methods

Flow cytometry was performed to analyse TREM-1 and TREM-2 expression on CD14⁺ cells in bronchoalveolar lavage fluid from patients having sarcoidosis or HP and a control group.

Results

The study proved increased TREM-1 expression on alveolar macrophages in pulmonary sarcoidosis and diminished TREM-1 expression in HP-Sarcoidosis: median: 76.7; HP: median: 29.9; control: median: 53.3, (sarcoidosis versus HP: p < 0.001; sarcoidosis versus control: p < 0.05). TREM-2 expression was increased in both, sarcoidosis and HP-sarcoidosis: median: 34.79; HP: median: 36.00; control: median: 12.98, (sarcoidosis versus control: p < 0.05; HP versus control: p < 0.05). Correlation analysis showed negative correlation between TREM-1 and total number of CD8⁺ cytotoxic T cells. In sarcoidosis TREM-1 expression decreased with changes of HRCT image, decrease in CD4/CD8 ratio and decrease in DLCO.

Conclusions

Differences in TREM receptor expression in sarcoidosis (increase in TREM-1 and TREM-2) and HP (increase in TREM-2) and correlation analysis suggests that activation via TREM may participate in typical immunological characteristics of sarcoidosis and HP.

Gastrointestinal Coinfection Promotes Chlamydial Pathogenicity in the Genital Tract

Sexually transmitted Chlamydia, which can cause fibrotic pathology in women's genital tracts, is also frequently detected in the gastrointestinal tract. However, the medical significance of the gastrointestinal Chlamydia remains unclear. A murine Chlamydia readily spreads from the mouse genital tract to the gastrointestinal tract while inducing oviduct fibrotic blockage or hydrosalpinx. We previously proposed a two-hit model in which the mouse gastrointestinal Chlamydia might induce the second hit to promote genital tract pathology, and we are now providing experimental evidence for testing the hypothesis. First, chlamydial mutants that are attenuated in inducing hydrosalpinx in the genital tract also reduce their colonization in the gastrointestinal tract, leading to a better correlation of chlamydial induction of hydrosalpinx with chlamydial colonization in the gastrointestinal tract than in the genital tract. Second, intragastric coinoculation with a wild-type Chlamydia rescued an attenuated Chlamydia mutant to induce hydrosalpinx, while the chlamydial mutant infection in the genital tract alone was unable to induce any significant hydrosalpinx. Finally, the coinoculated gastrointestinal Chlamydia failed to directly spread to the genital tract lumen, suggesting that gastrointestinal Chlamydia may promote genital pathology via an indirect mechanism. Thus, we have demonstrated a significant role of gastrointestinal Chlamydia in promoting pathology in the genital tract possibly via an indirect mechanism. This study provides a novel direction/dimension for further investigating chlamydial pathogenic mechanisms.

CD4+CXCR4+ T cells as a novel prognostic biomarker in patients with idiopathic inflammatory myopathy-associated interstitial lung disease

BACKGROUD

There is an unmet need for the development of new biomarkers for idiopathic inflammatory myopathy-associated interstitial lung disease (IIM-ILD).

METHODS

Peripheral CD4+CXCR4+ T cells, stromal cell-derived factor-1 and Krebs von den Lungen-6 were measured in patients with IIM-ILD (n = 85) and controls. The relation to pulmonary functions, high-resolution CT scores, specific clinical phenotypes and survival was analysed. Cytokine-expression profiling of these CD4+CXCR4+ T cells and their co-culture with pulmonary fibroblasts were conducted.

RESULTS

The peripheral percentages of CD4+CXCR4+ T cells were significantly elevated in IIM-ILD patients, and correlated with high-resolution CT score (r = 0.7136, P < 0.0001) and pulmonary function impairments, such as percentage of forced volume vital capacity (r = -0.4734, P = 0.0005). They were associated with anti-melanoma differentiation-associated gene 5 autoantibodies and the amyopathic DM phenotype. In IIM-ILD, peripheral percentages of CD4+CXCR4+ T cells ⩾30% revealed a 6-month mortality as high as 47%. These CD4+CXCR4+ T cells express high levels of IL-21 and IL-6. In vitro blockade of IL-21 signalling by neutralization of IL-21 or Janus kinase inhibitor could abolished the fibroblast proliferation.

CONCLUSION

Overall, peripheral CD4+CXCR4+ T cells appear to be a potentially valuable novel biomarker associated with the severity and prognosis of IIM-ILD. They promote pulmonary fibroblast proliferation via IL-21, which may herald future targeted treatments for this severe disease.

PD-1/PD-L1 Pathway Mediates the Alleviation of Pulmonary Fibrosis by Human Mesenchymal Stem Cells in Humanized Mice

Pulmonary fibrosis is a chronic progressive lung disease with few treatments. Human mesenchymal stem cells (MSCs) have been shown to be beneficial in pulmonary fibrosis because they have immunomodulatory capacity. However, there is no reliable model to test the therapeutic effect of human MSCs in vivo. To mimic pulmonary fibrosis in humans, we established a novel bleomycin-induced pulmonary fibrosis model in humanized mice. With this model, the benefit of human MSCs in pulmonary fibrosis and the underlying mechanisms were investigated. In addition, the relevant parameters in patients with pulmonary fibrosis were examined. We demonstrate that human CD8⁺ T cells were critical for the induction of pulmonary fibrosis in humanized mice. Human MSCs could alleviate pulmonary fibrosis and improve lung function by suppressing bleomycin-induced human T-cell infiltration and proinflammatory cytokine production in the lungs of humanized mice. Importantly, alleviation of pulmonary fibrosis by human MSCs was mediated by the PD-1/programmed death-ligand 1 pathway. Moreover, abnormal PD-1 expression was found in circulating T cells and lung tissues of patients with pulmonary fibrosis. Our study supports the potential benefit of targeting the PD-1/programmed death-ligand 1 pathway in the treatment of pulmonary fibrosis.

Activation of dendritic cells by crosslinked collagen hydrogels (artificial corneas) varies with their composition

Activated T cells are known to promote fibrosis, a major complication limiting the range of polymeric hydrogels as artificial corneal implants. As T cells are activated by dendritic cells (DC), minimally activating hydrogels would be optimal. In this study, we evaluated the ability of a series of engineered (manufactured/fabricated) and natural collagen matrices to either activate DC or conversely induce DC apoptosis in vitro. Bone marrow DC were cultured on a series of singly and doubly crosslinked hydrogels (made from recombinant human collagen III [RHCIII] or collagen mimetic peptide [CMP]) or on natural collagen-containing matrices, Matrigel^TM and de-cellularised mouse corneal stroma. DC surface expression of major histocompatibility complex Class II and CD86 as well as apoptosis markers were examined. Natural matrices induced low levels of DC activation and maintained a "tolerogenic" phenotype. The same applied to singly crosslinked CMP-PEG gels. RHCIII gels singly crosslinked using either N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide with the coinitiator N-hydroxy succinimide (EDC-NHS) or N-cyclohexyl-N-(2-morpholinoethyl)carbodiimide metho-p-toulenesulfonate with NHS (CMC-NHS) induced varying levels of DC activation. In contrast, however, RHCIII hydrogels incorporating an additional polymeric network of 2-methacryloyloxyethyl phosphorylcholine did not activate DC but instead induced DC apoptosis, a phenomenon observed in natural matrices. This correlated with increased DC expression of leukocyte-associated immunoglobulin-like receptor-1. Despite low immunogenic potential, viable tolerogenic DC migrated into and through both natural and manufactured RHCIII gels. These data show that the immunogenic potential of RHCIII gels varies with the nature and composition of the gel. Preclinical evaluation of hydrogel immunogenic/fibrogenic potential is recommended.

T-cell positioning by chemokines in autoimmune skin diseases

Autoimmune skin diseases are complex processes in which autoreactive cells must navigate through the skin tissue to find their targets. Regulatory T cells in the skin help to mitigate autoimmune inflammation and may in fact be responsible for the patchy nature of these conditions. In this review, we will discuss chemokines that are important for global recruitment of T cell populations to the skin during disease, as well as signals that fine-tune their localization and function. We will describe prototypical disease responses and chemokine families that mediate these responses. Lastly, we will include an overview of chemokine-targeting drugs that have been tested as new treatment strategies for autoimmune skin diseases.

Circulating follicular helper T cells are increased in systemic sclerosis and promote plasmablast differentiation through the IL-21 pathway which can be inhibited by ruxolitinib

OBJECTIVES

Systemic sclerosis (SSc) is an autoimmune disease characterised by widespread fibrosis, microangiopathy and autoantibodies. Follicular helper T (Tfh) cells CD4⁺CXCR5⁺PD-1⁺ cooperate with B lymphocytes to induce the differentiation of plasmocytes secreting immunoglobulins (Ig). Circulating Tfh (cTfh) cells are increased in several autoimmune diseases. However, there are no data about cTfh cells and their interaction with B cells in SSc. The aim of this study was to perform a quantitative and functional analysis of cTfh cells in SSc.

METHODS

Using flow cytometry, we analysed cTfh cells from 50 patients with SSc and 32 healthy controls (HC). In vitro coculture experiments of sorted cTfh and B cells were performed for functional analysis. IgG and IgM production were measured by ELISA.

RESULTS

We observed that cTfh cell numbers are increased in patients with SSc compared with HC. Furthermore, the increase in cTfh cells was more potent in patients with severe forms of SSc such as diffuse SSc and in the presence of arterial pulmonary hypertension. cTfh cells from patients with SSc present an activated Tfh phenotype, with high expression of BCL-6, increased capacity to produce IL-21 in comparison with healthy controls. In vitro, cTfh cells from patients with SSc had higher capacity to stimulate the differentiation of CD19⁺CD27⁺CD38^hi B cells and their secretion of IgG and IgM through the IL-21 pathway than Tfh cells from healthy controls. Blocking IL-21R or using the JAK1/2 inhibitor ruxolitinib reduced the Tfh cells' capacity to stimulate the plasmablasts and decreased the Ig production.

CONCLUSIONS

Circulating Tfh cells are increased in SSc and correlate with SSc severity. The IL-21 pathway or JAK1/2 blockade by ruxolitinib could be a promising strategy in the treatment of SSc.

Chlamydia Spreading from the Genital Tract to the Gastrointestinal Tract - A Two-Hit Hypothesis

Chlamydia trachomatis, a leading bacterial cause of sexually transmitted infection-induced infertility, is frequently detected in the gastrointestinal tract. Chlamydia muridarum, a model pathogen for investigating C. trachomatis pathogenesis, readily spreads from the mouse genital tract to the gastrointestinal tract, establishing long-lasting colonization. C. muridarum mutants, despite their ability to activate acute oviduct inflammation, are attenuated in inducing tubal fibrosis and are no longer able to colonize the gastrointestinal tract, suggesting that the spread of C. muridarum to the gastrointestinal tract may contribute to its pathogenicity in the upper genital tract. However, gastrointestinal C. muridarum cannot directly autoinoculate the genital tract. Both antigen-specific CD8⁺ T cells and profibrotic cytokines, such as TNFα and IL-13, are essential for C. muridarum to induce tubal fibrosis; this may be induced by the gastrointestinal C. muridarum, as a second hit, to transmucosally convert tubal repairing - initiated by C. muridarum infection of tubal epithelial cells (serving as the first hit) - into pathogenic fibrosis. Testing the two-hit mouse model should both add new knowledge to the growing list of mechanisms by which gastrointestinal microbes contribute to pathologies in extragastrointestinal tissues and provide information for investigating the potential role of gastrointestinal C. trachomatis in human chlamydial pathogenesis.

Monocyte-derived alveolar macrophages drive lung fibrosis and persist in the lung over the life span

Misharin et al. elucidate the fate and function of monocyte-derived alveolar macrophages during the course of pulmonary fibrosis. These cells persisted throughout the life span, were enriched for the expression of profibrotic genes, and their genetic ablation ameliorated development of pulmonary fibrosis.

Little is known about the relative importance of monocyte and tissue-resident macrophages in the development of lung fibrosis. We show that specific genetic deletion of monocyte-derived alveolar macrophages after their recruitment to the lung ameliorated lung fibrosis, whereas tissue-resident alveolar macrophages did not contribute to fibrosis. Using transcriptomic profiling of flow-sorted cells, we found that monocyte to alveolar macrophage differentiation unfolds continuously over the course of fibrosis and its resolution. During the fibrotic phase, monocyte-derived alveolar macrophages differ significantly from tissue-resident alveolar macrophages in their expression of profibrotic genes. A population of monocyte-derived alveolar macrophages persisted in the lung for one year after the resolution of fibrosis, where they became increasingly similar to tissue-resident alveolar macrophages. Human homologues of profibrotic genes expressed by mouse monocyte-derived alveolar macrophages during fibrosis were up-regulated in human alveolar macrophages from fibrotic compared with normal lungs. Our findings suggest that selectively targeting alveolar macrophage differentiation within the lung may ameliorate fibrosis without the adverse consequences associated with global monocyte or tissue-resident alveolar macrophage depletion.

The Contribution of Immune Infiltrates to Ototoxicity and Cochlear Hair Cell Loss

Cells of the immune system have been shown to infiltrate the cochlea after acoustic trauma or ototoxic drug treatment; however, the contribution of the immune system to hair cell loss in the inner ear is incompletely understood. Most studies have concentrated on the immediate innate response to hair cell damage using CD45 as a broad marker for all immune cells. More recent studies have used RNA sequencing, GeneChip arrays and quantitative PCR to analyze gene expression in the entire cochlea after auditory trauma, leading to a better understanding of the chemokines and cytokines that attract immune cells to the cochlea. Immune suppression by blocking cytokines or immune receptors has been proven to suppress hair cell damage. However, it is now understood that not all immune cells are detrimental to the cochlea. CX3CR1+ resident macrophages protect hair cells from damage mediated by infiltrating immune cells. Systemically, the immune response is associated with both protection and pathology, and it has been implicated in the regeneration of certain tissues after injury. This review focuses on the studies of immune cells in various models of hearing loss and highlights the steps that can be taken to elucidate the connection between the immune response and hearing loss. The interplay between the immune system and tissues that were previously thought to be immune privileged, such as the cochlea, is an emerging research field, to which additional studies of the immune component of the cochlear response to injury will make an important contribution.

Comparative study of two models of combined pulmonary fibrosis and emphysema in mice

Combined pulmonary fibrosis and emphysema (CPFE) is an "umbrella term" encompassing emphysema and pulmonary fibrosis, but its pathogenesis is not known. We established two models of CPFE in mice using tracheal instillation with bleomycin (BLM) or murine gammaherpesvirus 68 (MHV-68). Experimental mice were divided randomly into four groups: A (normal control, n=6), B (emphysema, n=6), C (emphysema+MHV-68, n=24), D (emphysema+BLM, n=6). Group C was subdivided into four groups: C1 (sacrificed on day 367, 7 days after tracheal instillation of MHV-68); C2 (day 374; 14days); C3 (day 381; 21days); C4 (day 388; 28days). Conspicuous emphysema and interstitial fibrosis were observed in BLM and MHV-68 CPFE mouse models. However, BLM induced diffuse pulmonary interstitial fibrosis with severely diffuse pulmonary inflammation; MHV-68 induced relatively modest inflammation and fibrosis, and the inflammation and fibrosis were not diffuse, but instead around bronchioles. Inflammation and fibrosis were detectable in the day-7 subgroup and reached a peak in the day-28 subgroup in the emphysema + MHV-68 group. Levels of macrophage chemoattractant protein-1, macrophage inflammatory protein-1α, interleukin-13, and transforming growth factor-β1 in bronchoalveolar lavage fluid were increased significantly in both models. Percentage of apoptotic type-2 lung epithelial cells was significantly higher; however, all four types of cytokine and number of macrophages were significantly lower in the emphysema+MHV-68 group compared with the emphysema +BLM group. The different changes in pathology between BLM and MHV-68 mice models demonstrated different pathology subtypes of CPFE: macrophage infiltration and apoptosis of type-II lung epithelial cells increased with increasing pathology score for pulmonary fibrosis.

Skin fibrosis: Models and mechanisms

Matrix synthesis, deposition and remodeling are complex biological processes that are critical in development, maintenance of tissue homeostasis and repair of injured tissues. Disturbances in the regulation of these processes can result in severe pathological conditions which are associated with tissue fibrosis as e.g. in Scleroderma, cutaneous Graft-versus-Host-Disease, excessive scarring after trauma or carcinogenesis. Therefore, finding efficient treatments to limit skin fibrosis is of major clinical importance. However the pathogenesis underlying the development of tissue fibrosis is still not entirely resolved. In recent years progress has been made unraveling the complex cellular and molecular mechanisms that determine fibrosis. Here we provide an overview of established and more recently developed mouse models that can be used to investigate the mechanisms of skin fibrosis and to test potential therapeutic approaches.