Radiation-induced fibrosis: Mechanisms and therapeutic strategies from an immune microenvironment perspective

Radiation-induced fibrosis (RIF) is a severe chronic complication of radiotherapy (RT) manifested by excessive extracellular matrix (ECM) components deposition within the irradiated area. The lung, heart, skin, jaw, pelvic organs and so on may be affected by RIF, which hampers body functions and quality of life. There is accumulating evidence suggesting that the immune microenvironment may play a key regulatory role in RIF. This article discussed the synergetic or antagonistic effects of immune cells and mediators in regulating RIF's development. Several potential preventative and therapeutic strategies for RIF were proposed based on the immunological mechanisms to provide clinicians with improved cognition and clinical treatment guidance.

Acute exacerbation of idiopathic pulmonary fibrosis disease: a diagnosis model in China

OBJECTIVE

To develop and validate a diagnosis model to inform risk stratified decisions for idiopathic pulmonary fibrosis patients experiencing acute exacerbations (AE-IPF).

METHODS

In this retrospective cohort study performed from 1 January 2016 to 31 December 2022, we used data from the West China Hospital of Sichuan University for model development and validation. Blood test results and the underlying diseases of patients were collected through the HIS system and LIS system. An algorithm for filtering candidate variables based on least absolute shrinkage and selection operator (LASSO) regression. Logistic regression was performed to develop the risk model. Multiple imputation handled missing predictor data. Model performance was assessed through calibration and diagnostic odds ratio.

RESULTS

311 and 133 participants were included in the development and validation cohorts, respectively. 3 candidate predictors (29 parameters) were included. A logistic regression analysis revealed that dyspnea, percentage of CD4+  T-lymphocytes, and percentage of monocytes are independent risk factors for AE-IPF. Nomographic model was constructed using these independent risk factors, and the C-index was 0.69. For internal validation, the C-index was 0.69, and that indicated good accuracy. Diagnostic odds ratio was 5.40. Meanwhile, in mild, moderate, and severe subgroups, AE positivity rates were 0.37, 0.47, and 0.81, respectively. The diagnostic model can classify patients with AE-IPF into different risk classes based on dyspnea, percentage of CD4+  T-lymphocytes, and percentage of monocytes.

CONCLUSION

A diagnosis model was developed and validated that used information collected from HIS system and LIS system and may be used to risk stratify idiopathic pulmonary fibrosis patients experiencing acute exacerbations.

Acute Exacerbations of Interstitial Lung Diseases: Focus on Biomarkers

Interstitial lung diseases (ILDs) are a large group of pulmonary disorders characterized histologically by the cardinal involvement of the pulmonary interstitium. The prototype of ILDs is idiopathic pulmonary fibrosis (IPF), an incurable disease characterized by progressive distortion and loss of normal lung architecture through unchecked collagen deposition. Acute exacerbations are dramatic events during the clinical course of ILDs, associated with high morbidity and mortality. Infections, microaspiration, and advanced lung disease might be involved in the pathogenesis of acute exacerbations. Despite clinical scores, the prediction of the onset and outcome of acute exacerbations is still inaccurate. Biomarkers are necessary to characterize acute exacerbations better. We review the evidence for alveolar epithelial cell, fibropoliferation, and immunity molecules as potential biomarkers for acute exacerbations of interstitial lung disease.

CXCL12/CXCR4: An amazing challenge and opportunity in the fight against fibrosis

Fibrosis is a pathological process caused by abnormal wound healing response, which often leads to excessive deposition of extracellular matrix, distortion of organ architecture, and loss of organ function. Aging is an important risk factor for the development of organ fibrosis. C-X-C receptor 4 (CXCR4) is the predominant chemokine receptor on fibrocytes, C-X-C motif ligand 12 (CXCL12) is the only ligand of CXCR4. Accumulated evidence have confirmed that CXCL12/CXCR4 can be involved in multiple pathological mechanisms in fibrosis, such as inflammation, immunity, epithelial-mesenchymal transition, and angiogenesis. In addition, CXCL12/CXCR4 have also been shown to improve fibrosis levels in many organs including the heart, liver, lung and kidney; thus, they are promising targets for anti-fibrotic therapy. Notably, inhibitors of CXCL12 or CXCR4 also play an important role in various fibrosis-related diseases. In summary, this review systematically summarizes the role of CXCL12/CXCR4 in fibrosis, and this information is of great significance for understanding CXCL12/CXCR4. This will also contribute to the design of further studies related to CXCL12/CXCR4 and fibrosis, and shed light on potential therapies for fibrosis.

Regulatory Immune Cells in Idiopathic Pulmonary Fibrosis: Friends or Foes?

The immune system is receiving increasing attention for interstitial lung diseases, as knowledge on its role in fibrosis development and response to therapies is expanding. Uncontrolled immune responses and unbalanced injury-inflammation-repair processes drive the initiation and progression of idiopathic pulmonary fibrosis. The regulatory immune system plays important roles in controlling pathogenic immune responses, regulating inflammation and modulating the transition of inflammation to fibrosis. This review aims to summarize and critically discuss the current knowledge on the potential role of regulatory immune cells, including mesenchymal stromal/stem cells, regulatory T cells, regulatory B cells, macrophages, dendritic cells and myeloid-derived suppressor cells in idiopathic pulmonary fibrosis. Furthermore, we review the emerging role of regulatory immune cells in anti-fibrotic therapy and lung transplantation. A comprehensive understanding of immune regulation could pave the way towards new therapeutic or preventive approaches in idiopathic pulmonary fibrosis.

Metabolic changes induced by TGF-β1 via reduced expression of phosphatidylserine decarboxylase during myofibroblast transition

Metabolic alteration is increasingly recognized as an important pathogenic process that underlies fibrosis across many organ types, and metabolically targeted therapies could become important strategies for reducing fibrosis. In present study, target enzymes that are involved in changes in phospholipid metabolism during fibroblast-to-myofibroblast transition induced by transforming growth factor beta 1 (TGF-β1) were examined. Different amounts of phospholipids were found in the 2 groups. In response to TGF-β1 stimulation, 17 lipids decreased and 17 increased. The latter included the phospholipids phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylethanolamine (PE). Furthermore, among the rate-limiting enzymes that regulate these phospholipids, phosphatidylserine decarboxylase (PISD), which controls conversion of PS to PE and is localized in mitochondria, decreased in response to TGF-β1. Knockdown of PISD alone without TGF-β1 stimulation increased expression of α-smooth muscle actin mRNA and production of total collagen. Taken together, these results indicate that PISD is involved in the mechanism of fibrogenesis by regulating phospholipid metabolism.

CXCR4+ cells are increased in lung tissue of patients with idiopathic pulmonary fibrosis

BACKGROUND

CXCR4, a transmembrane-receptor located on epithelial cells that is activated by CXCL12, may have a role in IPF via migration of CXCR4⁺ fibrocytes to the lung. However, its expression has not been fully characterised in idiopathic pulmonary fibrosis (IPF) or other fibrotic interstitial lung diseases (ILDs). CXCL12 is constitutively expressed in the bone marrow, and levels of CXCR4 regulate control of this signalling pathway. The aim of this study was to profile the expression of CXCR4 in lung tissue and peripheral circulation of patients with IPF and other fibrotic ILDs.

METHODS

Expression of CXCR4 on peripheral blood mononuclear cells (PBMCs) was examined by flow cytometry in 20 patients with IPF and 10 age-matched non-disease control (NDC) donors. Levels of CXCL12 in human plasma were measured by ELISA. Expression of CXCR4, CXCL12, CD45, and e-cadherin was assessed in IPF (n = 10), other fibrotic ILD (n = 8) and NDC (n = 10) lung tissue by multiplex immunohistochemistry (OPAL) and slides were scanned using a Vectra 3 scanner. Cells were quantified with computer automated histological analysis software (HALO).

RESULTS

In blood, the number of CXCR4⁺ cells was lower but the level of CXCL12 was higher in patients with IPF compared to NDC donors. Elevated CXCR4 expression was detected in lung tissue from patients with IPF and other fibrotic ILDs compared to NDC. There were higher levels of CXCR4⁺/e-cadherin⁺/CXCL12⁺ (epithelial) cells in IPF lung tissue compared to NDC, but there was no difference in the numbers of CXCR4⁺/CD45⁺/CXCL12⁺ (myeloid) cells between the two groups.

CONCLUSIONS

This report demonstrates that CXCR4 is overexpressed not only in IPF but also in other ILDs and expression is particularly prominent within both honeycomb cysts and distal airway epithelium. This observation supports the hypothesis that CXCR4 may drive tissue fibrosis through binding its specific ligand CXCL12. Although CXCR4 expressing cells could be either of epithelial or myeloid origin it appears that the former is more prominent in IPF lung tissue. Further characterization of the cells of the honeycomb cyst may lead to a better understanding of the fibrogenic processes in IPF and other end-stage fibrotic ILDs.

Regulatory T cells are a double-edged sword in pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic progressive interstitial lung disease. The pathogenesis of PF has not been clearly elucidated, and there is no obvious effective treatment to arrest the progression of PF to date. A long-term chronic inflammatory response and inappropriate repair process after lung injury are important causes and pathological processes of PF. As an influential type of the body's immune cells, regulatory T cells (Tregs) play an irreplaceable role in inhibiting the inflammatory response and promoting the repair of lung tissue. However, the exact roles of Tregs in the process of PF have not been clearly established, and the available literature concerning the roles of Tregs in PF are contradictory. First, Tregs can advance the progression of pulmonary fibrosis by secreting platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β) and other related factors, promoting epithelial-mesenchymal transition (EMT) and affecting the Th1 and Th2 balance, etc. Second, Tregs can inhibit PF by promoting the repair of epithelial cell damage, inhibiting the accumulation of fibroblasts, and strongly inhibiting the production and function of other related pro-inflammatory factors and pro-inflammatory cells. Accordingly, in this review, we focus on the multiple roles of Tregs in different models and different pulmonary fibrosis phases, thereby providing theoretical support for a better understanding of the multiple roles of these cells in PF and a theoretical basis for identifying targets for PF therapy.

Aryl hydrocarbon receptor signals attenuate lung fibrosis in the bleomycin-induced mouse model for pulmonary fibrosis through increase of regulatory T cells

BACKGROUND

Interstitial lung disease (ILD) is a serious complication of connective tissue diseases (CTDs). Although immune dysregulation triggered by genetic and environmental factors is thought to provoke inflammation and subsequent fibrosis, precise mechanisms of these processes remain unclear. Recent reports suggest that activation of aryl hydrocarbon receptor (AhR) signals by various ligands such as tryptophan derivatives can induce hyper-immune responses and are involved in autoimmunity. We investigated the effects of AhR signals on the process of lung fibrosis and changes in immunological features using a bleomycin (BLM)-induced lung fibrosis mouse model.

METHODS

BLM was administered intratracheally to C57BL/6JJcl mice and either 5,11-dihydroindolo[3,2-b]carbazole-6-carboxaldehyde (FICZ), a natural AhR ligand, or vehicle was subsequently injected intraperitoneally on day 0, 1, and 2 from BLM administration. Mice were sacrificed at week 3, and lung fibrosis was quantified by the histological changes using the Ashcroft score and deposition of soluble collagen levels in the lung using Sircol assay. The population of immune cells infiltrated into the lungs was analyzed using flow cytometry.

RESULTS

Both the Ashcroft score and soluble collagen level in FICZ-treated mice were significantly lower than those in the vehicle group. Moreover, the survival rate of FICZ-treated mice was significantly higher than that of control mice during the 3 weeks after treatment. Interestingly, flow cytometric analysis revealed that the number of CD4⁺Foxp3⁺ regulatory T cells (Tregs) was significantly increased and CD4⁺IFNγ⁺ and γδ⁺IL-17A⁺ T cells were decreased in the lungs of FICZ-treated mice, while the total number of T, B, and NK cells were unaffected by FICZ treatment.

CONCLUSIONS

Our findings suggest that stimulation of AhR signals attenuated lung fibrosis by increasing Tregs and suppressing inflammatory T cell subsets in a BLM-induced fibrosis model. AhR signaling pathways may therefore be useful therapeutic targets for connective tissue disease-associated ILD.

The autocrine CXCR4/CXCL12 axis contributes to lung fibrosis through modulation of lung fibroblast activity

The C-X-C Motif Chemokine Receptor 4/C-X-C Motif Chemokine Ligand 12 (CXCR4/CXCL12) axis has been implicated in the pathogenesis of pulmonary fibrosis. However, the mechanisms governing this remain to be determined. The current study demonstrated that human lung fibroblasts (HLFs) exhibit high CXCL12 expression and also exhibit high expression of its corresponding receptor CXCR4. Exogenous CXCL12 was revealed to significantly promote the migration and proliferation of HLFs, and potentiate CXCR4 expression. These effects were demonstrated to be inhibited by AMD3100, which is an antagonist of CXCR4. Lung and bronchoalveolar lavage fluid CXCR4 and CXCL12 expression was upregulated by in vivo bleomycin administration, which was partially inhibited by pre-treatment with AMD3100. AMD3100 also reduced lung collagen content in the bleomycin model. Inhibiting CXCR4 was indicated to ameliorate the lung compliance and resistance of pulmonary fibrosis. In conclusion, the results of the present study suggested that autocrine CXCR4/CXCL12 axis is an important mechanism underlying the pathogenesis of idiopathic pulmonary fibrosis, and may serve as a potential therapeutic target that can be used in the treatment of pulmonary disease.

Lymphoid Interstitial Pneumonia in Common Variable Immune Deficiency - Case Report With Disease Monitoring in Various Therapeutic Options: Pleiotropic Effects of Rituximab Regimens

Lymphoid interstitial pneumonia (LIP) is a rare lymphoproliferative disease. LIP in common variable immunodeficiency (CVID) was observed in a patient during immunomodulatory therapy after progression of the disease (i.e., glucocorticoids, immunoglobulin dose escalation, and finally rituximab). Due to humoral immunodeficiency and serious serum sickness rituximab was used initially at a low dose (150 mg/m² weekly). It resulted in temporary remission with the decrease of serum paraproteinemia, β₂-microglobulin (β2M) and SUV decrease as well as increase of FVC. Owing to the relapse after 6-month remission in the second cycle a standard dose of rituximab was used (375 mg/m²). Therapeutic regimen with 375 mg/m² of Rtx in optimal schedule (i.e., every 3 weeks) resulted in no longer remission but higher incidence of opportunistic infections. Finally, after another cycle of immunotherapy FVC, paraproteinemia and β2M level normalization were observed as well as the decrease of severe splenomegaly. In laboratory and immunological progress the increase of NK and NKT cells was observed after the initial dose but the standard one caused NK cell increase only. Unfortunately, the decrease of CD19+Bcells was comparable between both doses, as was the decline of FoxP3+ regulatory T cell. On the contrary, after the low dose absolute T cell (both CD4 and CD8) number decreased but after the standard one - it normalized. Rtx (especially in low dose) brought further increase of persistent T cell activation (CD38+ T cells made up 79%). Innate immune response and the decrease of Treg are a compensatory pathways for the decrease of B and T cells. Immunodeficiency requires a different investigative approach to a immunotherapy. Clinical Trial Registration: ClinicalTrials.gov, NCT02789397.

Resolution of bleomycin-induced murine pulmonary fibrosis via a splenic lymphocyte subpopulation

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with high mortality, and the pathogenesis of the disease is still incompletely understood. Although lymphocytes, especially CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs), have been implicated in the development of IPF, contradictory results have been reported regarding the contribution of Tregs to fibrosis both in animals and humans. The aim of this study was to investigate whether a specific T cell subset has therapeutic potential in inhibiting bleomycin (BLM)-induced murine pulmonary fibrosis.

Methods

C57BL/6 mice received BLM (100 mg/kg body weight) with osmotic pumps (day 0), and pulmonary fibrosis was induced. Then, splenocytes or Tregs were adoptively transferred via the tail vein. The lungs were removed and subjected to histological and biochemical examinations to study the effects of these cells on pulmonary fibrosis, and blood samples were collected by cardiac punctures to measure relevant cytokines by enzyme-linked immunosorbent assay. Tregs isolated from an interleukin (IL)-10 knock-out mice were used to assess the effect of this mediator. To determine the roles of the spleen in this model, spleen vessels were carefully cauterized and the spleen was removed either on day 0 or 14 after BLM challenge.

Results

Splenocytes significantly ameliorated BLM-induced pulmonary fibrosis when they were administered on day 14. This effect was abrogated by depleting Tregs with an anti-CD25 monoclonal antibody. Adoptive transfer of Tregs on day 14 after a BLM challenge significantly attenuated pulmonary fibrosis, and this was accompanied by decreased production of fibroblast growth factor (FGF) 9-positive cells bearing the morphology of alveolar epithelial cells. In addition, BLM-induced plasma IL-10 expression reverted to basal levels after adoptive transfer of Tregs. Moreover, BLM-induced fibrocyte chemoattractant chemokine (CC motif) ligand-2 production was significantly ameliorated by Treg adoptive transfer in lung homogenates, accompanied by reduced accumulation of bone-marrow derived fibrocytes. Genetic ablation of IL-10 abrogated the ameliorating effect of Tregs on pulmonary fibrosis. Finally, splenectomy on day 0 after a BLM challenge significantly ameliorated lung fibrosis, whereas splenectomy on day 14 had no effect.

Conclusions

These findings warrant further investigations to develop a cell-based therapy using Tregs for treating IPF.

Biomarkers in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, debilitating, fibrotic lung disease leading to respiratory failure and ultimately to death. Being the prototype of interstitial lung diseases, IPF is characterized by marked heterogeneity regarding its clinical course. Despite significant progress in the understanding of its pathogenesis, we still cannot reliably predict the course of the disease and the response to treatment of an individual patient. Non-invasive biomarkers, in particular serum biomarkers, for the (early) diagnosis, differential diagnosis, prognosis and prediction of therapeutic response are urgently needed. Numerous molecules involved in alveolar epithelial cell injury, fibroproliferation and matrix remodeling as well as immune regulation have been proposed as potential biomarkers. Furthermore, genetic variants of TOLLIP, MUC5B, and other genes are associated with a differential response to treatment and with the development and/or the prognosis of IPF. Additionally, the bacterial signature in IPF lungs, as shown from microbiome analyses, as well as mitochondrial DNA seem to have promising roles as biomarkers. Moreover, combination of multiple biomarkers may identify comprehensive biomarker signatures in IPF patients. However, there is still a long way until these potential biomarkers complete or substitute for the clinical and functional parameters currently available for IPF.

Activated human T lymphocytes inhibit TGFβ-induced fibroblast to myofibroblast differentiation via prostaglandins D2 and E2

In pulmonary fibrosis (PF), fibroblasts and myofibroblasts proliferate and deposit excessive extracellular matrix in the interstitium, impairing normal lung function. Because most forms of PF have a poor prognosis and limited treatment options, PF represents an urgent unmet need for novel, effective therapeutics. Although the role of immune cells in lung fibrosis is unclear, recent studies suggest that T lymphocyte (T cell) activation may be impaired in PF patients. Furthermore, we have previously shown that activated T cells can produce prostaglandins with anti-scarring potential. Here, we test the hypothesis that activated T cells directly inhibit myofibroblast differentiation using a coculture system. Coculture with activated primary blood-derived T cells, from both healthy human donors and PF patients, inhibited transforming growth factor β-induced myofibroblast differentiation in primary human lung fibroblasts isolated from either normal or PF lung tissue. Coculture supernatants contained anti-fibrotic prostaglandins D₂ and E₂, and the inhibitory effect of coculture on myofibroblast differentiation was largely reversed when prostaglandin production was abrogated either by resting the T cells before coculture or via specific pharmacological inhibitors. Moreover, coculture conditions induced COX-2 in HLFs but not in T cells, suggesting that T cells deliver an activating signal to HLFs, which in turn produce anti-fibrotic prostaglandins. We show for the first time that coculture with activated primary human T lymphocytes strongly inhibits myofibroblast differentiation, revealing a novel cell-to-cell communication network with therapeutic implications for fibrotic lung diseases.

Skewed Lung CCR4 to CCR6 CD4+ T Cell Ratio in Idiopathic Pulmonary Fibrosis Is Associated with Pulmonary Function

Rationale

Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal lung disease. While it has been suggested that T cells may contribute to IPF pathogenesis, these studies have focused primarily on T cells outside of the pulmonary interstitium. Thus, the role of T cells in the diseased lung tissue remains unclear.

Objective

To identify whether specific CD4⁺ T cell subsets are differentially represented in lung tissue from patients with IPF.

Methods

CD4⁺ T cell subsets were measured in lung tissue obtained from patients with IPF at the time of lung transplantation, and from age- and gender-matched organ donors with no known lung disease. Subsets were identified by their surface expression of CCR4, CCR6, and CXCR3 chemokine receptors. CD4⁺ T cell subsets were correlated with measurements of lung function obtained prior to transplantation.

Results

Compared to controls, IPF patients had a higher proportion of lung CD4⁺ T cells, a higher proportion of CCR4⁺ CD4⁺ T cells, and a lower proportion of CCR6⁺ CD4⁺ T cells. The increase in CCR4⁺ CD4⁺ T cells in IPF lung tissue was not due to increased Tregs. Intriguingly, the increase in the ratio of CCR4⁺ cells to CCR6⁺ cells correlated significantly with better lung function.

Conclusion

Our findings suggest a new paradigm that not all T cell infiltrates in IPF lungs are detrimental, but instead, specialized subsets may actually be protective. Thus, augmentation of the chemokines that recruit protective T cells, while blocking chemokines that recruit detrimental T cells, may constitute a novel approach to IPF therapy.

Six-SOMAmer Index Relating to Immune, Protease and Angiogenic Functions Predicts Progression in IPF

RATIONALE

Biomarkers in easily accessible compartments like peripheral blood that can predict disease progression in idiopathic pulmonary fibrosis (IPF) would be clinically useful regarding clinical trial participation or treatment decisions for patients. In this study, we used unbiased proteomics to identify relevant disease progression biomarkers in IPF.

METHODS

Plasma from IPF patients was measured using an 1129 analyte slow off-rate modified aptamer (SOMAmer) array, and patient outcomes were followed over the next 80 weeks. Receiver operating characteristic (ROC) curves evaluated sensitivity and specificity for levels of each biomarker and estimated area under the curve (AUC) when prognostic biomarker thresholds were used to predict disease progression. Both logistic and Cox regression models advised biomarker selection for a composite disease progression index; index biomarkers were weighted via expected progression-free days lost during follow-up with a biomarker on the unfavorable side of the threshold.

RESULTS

A six-analyte index, scaled 0 to 11, composed of markers of immune function, proteolysis and angiogenesis [high levels of ficolin-2 (FCN2), cathepsin-S (Cath-S), legumain (LGMN) and soluble vascular endothelial growth factor receptor 2 (VEGFsR2), but low levels of inducible T cell costimulator (ICOS) or trypsin 3 (TRY3)] predicted better progression-free survival in IPF with a ROC AUC of 0.91. An index score ≥ 3 (group ≥ 2) was strongly associated with IPF progression after adjustment for age, gender, smoking status, immunomodulation, forced vital capacity % predicted and diffusing capacity for carbon monoxide % predicted (HR 16.8, 95% CI 2.2-126.7, P = 0.006).

CONCLUSION

This index, derived from the largest proteomic analysis of IPF plasma samples to date, could be useful for clinical decision making in IPF, and the identified analytes suggest biological processes that may promote disease progression.

CD4(+)CD25(hi)Foxp3(+) Cells Exacerbate Bleomycin-Induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis is a fatal lung disease with a median survival of 2 to 5 years. A decade of studies has downplayed inflammation contributing to its pathogenesis. However, these studies preceded the discovery of regulatory T cells (Tregs) and all of their functions. On the basis of human studies demonstrating Tregs can decrease graft-versus-host disease and vasculitides, there is consideration of their use to treat idiopathic pulmonary fibrosis. We hypothesized that Treg therapy would attenuate the fibroplasia involved in a preclinical murine model of pulmonary fibrosis. IL-2 complex was used in vivo to expand CD4(+)CD25(hi)Foxp3(+) cells in the lung during intratracheal bleomycin challenge; however, this unexpectedly led to an increase in lung fibrosis. More important, this increase in fibrosis was a lymphocyte-dependent process. We corroborated these results using a CD4(+)CD25(hi)Foxp3(+) cellular-based therapy. Mechanistically, we demonstrated that CD4(+)CD25(hi)Foxp3(+) cells undergo alterations during bleomycin challenge and the IL-2 complex had no effect on profibrotic (eg, transforming growth factor-β) or type 17 immune response cytokines; however, there was a marked down-regulation of the type 1 and augmentation of the type 2 immune response cytokines from the lungs. Collectively, our animal studies show that a specific lung injury can induce Treg alterations, which can augment pulmonary fibrosis.

Inflammatory leukocyte phenotypes correlate with disease progression in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive deposition of extracellular matrix, worsening dyspnea, and eventual mortality. Pathogenesis of IPF is poorly understood and the role inflammation and activated leukocytes play in the disease process is controversial. Previous studies demonstrated that activated leukocyte subsets characterize IPF patients. We sought to validate this observation in a well-defined cohort of 35 IPF patients and to correlate the observed leukocyte phenotypes with robust parameters of disease progression. We demonstrate that in univariate and multivariate analyses, increases in the CD14hi, CD16hi subset of monocytes measured at baseline correlated with disease progression, with a threshold value >0.5% of the total peripheral blood mononuclear cells being a significant predictor for worse outcome. In addition, several T cell subsets, including CD25 expressing CD4 cells, and CXCR3 expressing CD4 and CD8 subsets correlated with disease progression when found in increased percentages in the peripheral blood of IPF patients when sampled at baseline. Somewhat surprising in comparison to previous literature, the CD4 T cells did not appear to have lost expression of the co-stimulatory molecule, CD28, but the CD8 T cells did. Taken together, these results are consistent with the presence of an inflammatory process in IPF patients who eventually progress. However, when longitudinal measurements of these same markers were examined, there was significant heterogeneity of expression and these biomarkers did not necessarily remain elevated in IPF patients with progressive disease. We interpret this heterogeneity to suggest that IPF patients experience episodic inflammatory events that once triggered, may lead to disease progression. This longitudinal heterogeneity in biomarker analyses may explain why such markers are not consistently measured in all IPF cohorts.

Peripheral depletion of NK cells and imbalance of the Treg/Th17 axis in idiopathic pulmonary fibrosis patients

The immune response plays an unsettled role in the pathogenesis of idiopathic pulmonary fibrosis (IPF), the contribution of inflammation being controversial as well. Emerging novel T cell sub-populations including regulatory T lymphocytes (Treg) and interleukin (IL)-17 secreting T helper cells (Th17) may exert antithetical actions in this scenario. Phenotype and frequency of circulating immune cell subsets were assessed by multi-parametric flow cytometry in 29 clinically stable IPF patients and 17 healthy controls. The interplay between Treg lymphocytes expressing transforming growth factor (TGF)-β and Th17 cells was also investigated. Proportion and absolute number of natural killer (NK) cells were significantly reduced in IPF patients in comparison with controls (p<0.001). Conversely, the proportion and absolute number of CD3(+)CD4(+)CD25(high)Foxp-3(+) cells were significantly increased in IPF patients (p=0.000). As in controls, almost the totality of cells (>90%) expressed TGF-β upon stimulation. Interestingly, the frequency of Th17 cells was significantly compromised in IPF patients (p=0.000) leading to an increased TGF-β/IL-17 ratio (4.2±2.3 vs 0.5±0.3 in controls, p=0.000). Depletion of NK and Th17 cells along with a not compromised Treg compartment delineate the existence of an "immune profile" that argue against the recent hypothesis of IPF as an autoimmune disease. Our findings along with the imbalance of the Treg/Th17 axis more closely suggest these immune perturbations to be similar to those observed in cancer. Clinical relevance, limitations and perspectives for future research are discussed.

FOXP3 inhibits NF-κB activity and hence COX2 expression in gastric cancer cells

Gastric cancer remains the main cause of cancer related deaths all over the world, and upregulated COX2 is a key player in its development. The mechanism as to how COX2 is regulated during the gastric cancer development is largely unknown. In this study, we found that the expression of COX2 was closely correlated with NF-κB activity. Strikingly, NF-κB activity was not absolutely consistent with its nuclear localization. Especially, in some cancer cell lines, such as MKN28, there were abundant nuclear localized NF-κB, while NF-κB luciferase activity in this cell line was relatively low. Furthermore, FOXP3 was found to be abundantly expressed in these cells. When the nuclear localized NF-κB expression was adjusted with the expression of FOXP3, it then correlated well with NF-κB activity. Molecularly, increased FOXP3 expression can interact with NF-κB and thus repress its activity. Knockdown of FOXP3 could increase NF-κB activity, COX2 expression, and cell migration. Taken together, our study revealed that function of FOXP3 as a negative regulator of NF-κB activity and thus plays a tumor suppressor role by reducing cell metastasis.

Cytokine-like factor 1 gene expression is enriched in idiopathic pulmonary fibrosis and drives the accumulation of CD4+ T cells in murine lungs: evidence for an antifibrotic role in bleomycin injury

Idiopathic pulmonary fibrosis (IPF) is a progressive and typically fatal lung disease. To gain insight into the pathogenesis of IPF, we reanalyzed our previously published gene expression data profiling IPF lungs. Cytokine receptor-like factor 1 (CRLF1) was among the most highly up-regulated genes in IPF lungs, compared with normal controls. The protein product (CLF-1) and its partner, cardiotrophin-like cytokine (CLC), function as members of the interleukin 6 (IL-6) family of cytokines. Because of earlier work implicating IL-6 family members in IPF pathogenesis, we tested whether CLF-1 expression contributes to inflammation in experimental pulmonary fibrosis. In IPF, we detected CLF-1 expression in both type II alveolar epithelial cells and macrophages. We found that the receptor for CLF-1/CLC signaling, ciliary neurotrophic factor receptor (CNTFR), was expressed only in type II alveolar epithelial cells. Administration of CLF-1/CLC to both uninjured and bleomycin-injured mice led to the pulmonary accumulation of CD4(+) T cells. We also found that CLF-1/CLC administration increased inflammation but decreased pulmonary fibrosis. CLF-1/CLC leads to significantly enriched expression of T-cell-derived chemokines and cytokines, including the antifibrotic cytokine interferon-γ. We propose that, in IPF, CLF-1 is a selective stimulus of type II alveolar epithelial cells and may potentially drive an antifibrotic response by augmenting both T-helper-1-driven and T-regulatory-cell-driven inflammatory responses in the lung.

The immune response to tumors as a tool toward immunotherapy

Until recently cancer medical therapy was limited to chemotherapy that could not differentiate cancer cells from normal cells. More recently with the remarkable mushroom of immunology, newer tools became available, resulting in the novel possibility to attack cancer with the specificity of the immune system. Herein we will review some of the recent achievement of immunotherapy in such aggressive cancers as melanoma, prostatic cancer, colorectal carcinoma, and hematologic malignancies. Immunotherapy of tumors has developed several techniques: immune cell transfer, vaccines, immunobiological molecules such as monoclonal antibodies that improve the immune responses to tumors. This can be achieved by blocking pathways limiting the immune response, such as CTLA-4 or Tregs. Immunotherapy may also use cytokines especially proinflammatory cytokines to enhance the activity of cytotoxic T cells (CTLs) derived from tumor infiltrating lymphocytes (TILs). The role of newly discovered cytokines remains to be investigated. Alternatively, an other mechanism consists in enhancing the expression of TAAs on tumor cells. Finally, monoclonal antibodies may be used to target oncogenes.

Cholesterol: An Inflammatory Compound

Obesity is one of the main rising causes of health problems in modern society and is correlated to type 2 diabetes mellitus, hypertension, heart disease and atherosclerosis. Bacterial products, endogenous substances such as oxidized LDL (ox-LDL) and heat shock proteins mediate activation of Toll-like receptors and reinforce the view that the innate immune system plays a key role in the genesis of atherosclerosis. In addition, natural killer T (NKT) cells respond to lipids presented via CD1d on APCs, and may also be able to affect atherosclerosis. All the main cell types involved in atherosclerosis such as endothelial cells, macrophages, T cells, smooth muscle cells and platelets express proinflammatory cytokines. In addition, CD4 ligation triggers the expression of adhesion molecules, cytokines and matrix metalloprotinease. IL-6 cytokines travels to the liver where it elicits acute phase response resolving in the release of serum amyloid-A C-reactive protein, fibrogen and plasminogen activator inhibitor-1. Therefore increasing body fat mass is associated with high levels of inflammatory cytokines such as IL-1 and TNF. In this study we revisit the interrelationship between fat and inflammation.