Cellular and humoral autoreactivity in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is associated with circulating antiepithelial antibodies

PURPOSE

Idiopathic pulmonary fibrosis (IPF) is a restrictive fibrotic lung disease of uncertain etiology. Alveolar epithelial injury may be one of the inciting triggers in the pathogenesis of this disorder. We hypothesized that circulating antibodies to alveolar epithelial and endothelial cells may be involved in the pathogenesis of IPF.

METHODS

Antibodies to alveolar epithelial and endothelial cells were analyzed by indirect immunofluorescence using alveolar epithelial cells (A549) and human umbilical vein endothelial cells respectively. IgG and IgM antibodies in patients' serum were evaluated. Patterns of immunofluorescence, including membranous, cytoplasmic, and nuclear staining, were analyzed by fluorescence microscopy. The severity of immunofluorescence was divided into mild, moderate, and severe categories. Fifty-six patients (IPF = 28, non-IPF ILD = 9, non-ILD control = 19) were evaluated for antiepithelial antibodies, and 28 patients (IPF = 12, non-IPF ILD = 3, non-ILD control = 13) were studied for antiendothelial antibodies.

RESULTS

Compared with control subjects, serum from IPF patients displayed significantly higher IgG binding to alveolar epithelial cells (P = 0.041) with a membranous pattern of immunofluorescence. However, there was no significant difference in immunofluorescence with IgG on endothelial cells (P = 0.165). In terms of IgM antibodies, there was no differential fluorescence observed for either epithelial or endothelial cells.

CONCLUSIONS

There is evidence of increased IgG antibodies directed against alveolar epithelium in IPF. These antibodies may play a significant role in the pathogenesis of this fibrotic disorder. The findings of this study suggest further evaluation of the role of immune mediated alveolar epithelial injury in IPF.

Autoantibody formation in human and rat studies of chronic rejection and primary graft dysfunction

Lung transplantation is considered a definitive treatment for many lung diseases. However, rejection and other pathologic entities are major causes of morbidity and mortality for lung transplant recipients. Primary graft dysfunction (PGD) and obliterative bronchiolitis (OB) are the leading causes of early and late mortality, respectively. While the immune basis of PGD has not been clearly defined, evidence is emerging about roles for autoantibodies in this process. Similarly, the pathogenesis of OB has been linked recently to autoimmunity. This review will highlight the current understanding of autoantibodies in PGD and OB post lung transplantation.

The distribution of immunomodulatory cells in the lungs of patients with idiopathic pulmonary fibrosis

We have characterized the immune system involvement in the disease processes of idiopathic pulmonary fibrosis in novel ways. To do so, we analyzed lung tissue from 21 cases of idiopathic pulmonary fibrosis and 21 (non-fibrotic, non-cancerous) controls for immune cell and inflammation-related markers. The immunohistochemical analysis of the tissue was grouped by patterns of severity in disease pathology. There were significantly greater numbers of CD68(+) and CD80(+) cells and significantly fewer CD3(+), CD4(+), and CD45RO(+) cells in areas of relatively (histologically) normal lung in biopsy samples from idiopathic pulmonary fibrosis patients compared with controls. In zones of active disease, characterized by epithelial cell regeneration and fibrosis, there were significantly more cells expressing CD4, CD8, CD20, CD68, CD80, chemokine receptor 6 (CCR6), S100, IL-17, tumor necrosis factor-α, and retinoic acid-related orphan receptors compared with histologically normal lung areas from idiopathic pulmonary fibrosis patients. Inflammation was implicated in these active regions by the cells that expressed retinoid orphan receptor-α, -β, and -γ, CCR6, and IL-17. The regenerating epithelial cells predominantly expressed these pro-inflammatory molecules, as evidenced by co-expression analyses with epithelial cytokeratins. Macrophages in pseudo-alveoli and CD3(+) T cells in the fibrotic interstitium also expressed IL-17. Co-expression of IL-17 with retinoid orphan receptors and epithelial cytoskeletal proteins, CD68, and CD3 in epithelial cells, macrophages, and T-cells, respectively, confirmed the production of IL-17 by these cell types. There was little staining for forkhead box p3, CD56, or CD34 in any idiopathic pulmonary fibrosis lung regions. The fibrotic regions had fewer immune cells overall. In summary, our study shows participation of innate and adaptive mononuclear cells in active-disease regions of idiopathic pulmonary fibrosis lung, where the regenerating epithelial cells appear to propagate inflammation. The regenerative mechanisms become skewed to ultimately result in lethal, fibrotic restriction of lung function.

Effect and safety of mycophenolate mofetil in idiopathic pulmonary fibrosis

Background. Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic interstitial lung disease with ineffective treatment. Mycophenolate mofetil (MMF) is an immunomodulatory agent which inhibits lymphocyte proliferation. Objective. We sought to determine the safety and efficacy profile of MMF in IPF patients. Methods. We retrospectively identified ten patients, who met the ATS/ERS 2000 criteria for IPF and received MMF 2 gr/day for 12 months. All of them had routine laboratory, pulmonary function and radiological (high resolution computed tomography-HRCT) data available and were enrolled in the study. Forced vital capacity (FVC), total lung capacity (TLC), diffusion capacity of the lung for carbon monoxide (DL_CO), 6-minute walking distance (6MWD), HRCT scans and routine laboratory data at treatment onset were compared with respective values 12 months after treatment onset. Results. There were no significant alterations in FVC, TLC, DL_CO and 6MWD pre- and 6 and 12 months post-treatment. HRCT evaluation showed deterioration of the total extent of disease (P = 0.002) and extent of ground-glass opacity (P = 0.02). No cases of clinically significant infection, leucopenia, or elevated liver enzymes were recorded. Conclusions. MMF is a safe therapeutic modality which failed to show a beneficial effect both in functional and radiological parameters in a small cohort of IPF patients.

Idiopathic pulmonary fibrosis-an epidemiological and pathological review

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease (ILD) affecting the pulmonary interstitium. Other forms of interstitial lung disease exist, and in some cases, an environmental etiology can be delineated. The diagnosis of IPF is typically established by high-resolution CT scan. IPF tends to have a worse prognosis than other forms of ILD. Familial cases of IPF also exist, suggesting a genetic predisposition; telomerase mutations have been observed to occur in familial IPF, which may also explain the increase in IPF with advancing age. Alveolar epithelial cells are believed to be the primary target of environmental agents that have been putatively associated with IPF. These agents may include toxins, viruses, or the autoantibodies found in collagen vascular diseases. The mechanism of disease is still unclear in IPF, but aberrations in fibroblast differentiation, activation, and proliferation may play a role. Epithelial-mesenchymal transition may also be an important factor in the pathogenesis, as it may lead to accumulation of fibroblasts in the lung and a disruption of normal tissue structure. Abnormalities in other components of the immune system, including T cells, B cells, and dendritic cells, as well as the development of ectopic lymphoid tissue, have also been observed to occur in IPF and may play a role in the stimulation of fibrosis that is a hallmark of the disease. It is becoming increasingly clear that the pathogenesis of IPF is indeed a complex and convoluted process that involves numerous cell types and humoral factors.

Novel therapeutic approaches for pulmonary fibrosis

Pulmonary fibrosis represents the end stage of a number of heterogeneous conditions and is, to a greater or lesser degree, the hallmark of the interstitial lung diseases. It is characterized by the excessive deposition of extracellular matrix proteins within the pulmonary interstitium leading to the obliteration of functional alveolar units and in many cases, respiratory failure. While a small number of interstitial lung diseases have known aetiologies, most are idiopathic in nature, and of these, idiopathic pulmonary fibrosis is the most common and carries with it an appalling prognosis - median survival from the time of diagnosis is less than 3 years. This reflects the lack of any effective therapy to modify the course of the disease, which in turn is indicative of our incomplete understanding of the pathogenesis of this condition. Current prevailing hypotheses focus on dysregulated epithelial-mesenchymal interactions promoting a cycle of continued epithelial cell injury and fibroblast activation leading to progressive fibrosis. However, it is likely that multiple abnormalities in a myriad of biological pathways affecting inflammation and wound repair - including matrix regulation, epithelial reconstitution, the coagulation cascade, neovascularization and antioxidant pathways - modulate this defective crosstalk and promote fibrogenesis. This review aims to offer a pathogenetic rationale behind current therapies, briefly outlining previous and ongoing clinical trials, but will focus on recent and exciting advancements in our understanding of the pathogenesis of idiopathic pulmonary fibrosis, which may ultimately lead to the development of novel and effective therapeutic interventions for this devastating condition.

Pulmonary fibrosis in response to environmental cues and molecular targets involved in its pathogenesis

Chronic lung injury resulting from a variety of different causes is frequently associated with the develop ment of pulmonary fibrosis in humans. Although the etiology of pulmonary fibrosis is generally unknown, several sources of evidence support the hypothesis that a number of environmental and occupational agents play an etiologic role in the pathogenesis of this disease. The agents discussed in this review include beryllium, nylon flock, textile printing aerosols, polyvinyl chloride and didecyldimethylammonium chloride. The authors also describe a variety of animal models, including genetically modified mice, in order to investigate the molecular mechanism of pulmonary fibrosis, focusing on chemokine receptors, regulatory T cells and transforming growth factor-β and bone morphogenetic protein signaling. Overall, we propose the concept of toxicological pulmonary fibrosis as a lung disease induced in response to environmental cues.

The HLA class II Allele DRB1*1501 is over-represented in patients with idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive and medically refractory lung disease with a grim prognosis. Although the etiology of IPF remains perplexing, abnormal adaptive immune responses are evident in many afflicted patients. We hypothesized that perturbations of human leukocyte antigen (HLA) allele frequencies, which are often seen among patients with immunologic diseases, may also be present in IPF patients.

Methods/Principal Findings

HLA alleles were determined in subpopulations of IPF and normal subjects using molecular typing methods. HLA-DRB1*15 was over-represented in a discovery cohort of 79 Caucasian IPF subjects who had lung transplantations at the University of Pittsburgh (36.7%) compared to normal reference populations. These findings were prospectively replicated in a validation cohort of 196 additional IPF subjects from four other U.S. medical centers that included both ambulatory patients and lung transplantation recipients. High-resolution typing was used to further define specific HLA-DRB1*15 alleles. DRB1*1501 prevalence in IPF subjects was similar among the 143 ambulatory patients and 132 transplant recipients (31.5% and 34.8%, respectively, p = 0.55). The aggregate prevalence of DRB1*1501 in IPF patients was significantly greater than among 285 healthy controls (33.1% vs. 20.0%, respectively, OR 2.0; 95%CI 1.3–2.9, p = 0.0004). IPF patients with DRB1*1501 (n = 91) tended to have decreased diffusing capacities for carbon monoxide (DL_CO) compared to the 184 disease subjects who lacked this allele (37.8±1.7% vs. 42.8±1.4%, p = 0.036).

Conclusions/Significance

DRB1*1501 is more prevalent among IPF patients than normal subjects, and may be associated with greater impairment of gas exchange. These data are novel evidence that immunogenetic processes can play a role in the susceptibility to and/or manifestations of IPF. Findings here of a disease association at the HLA-DR locus have broad pathogenic implications, illustrate a specific chromosomal area for incremental, targeted genomic study, and may identify a distinct clinical phenotype among patients with this enigmatic, morbid lung disease.

Identification of periplakin as a new target for autoreactivity in idiopathic pulmonary fibrosis

RATIONALE

Injury to alveolar epithelial cells is central to the pathophysiology of idiopathic pulmonary fibrosis (IPF). An abnormal autoimmune response directed against antigens of the alveolar epithelium may contribute to the disease.

OBJECTIVES

To detect circulating autoantibodies (autoAbs) directed against epithelial structures.

METHODS

We performed immunoblot by separating human placental amnion extract or alveolar epithelial cell (A549 cell line) proteins on polyacrylamide gels, blotting on nitrocellulose membranes, and incubating with serum from patients with IPF (n = 40) or healthy subjects (n = 40). Proteomic analysis and mass spectrometry characterized the target protein. Inhibition experiments performed with the correspondent recombinant protein confirmed our results.

MEASUREMENTS AND MAIN RESULTS

We identified IgG autoAbs recognizing a 200-kD protein in the serum of patients with IPF. Proteomic analysis identified this protein as human periplakin (PPL), a component of desmosomes. Anti-PPL Abs were found by immunoblot in both serum and bronchoalveolar lavage in patients with IPF: 16/40 (40%) of them were positive versus none of the control subjects. Immunohistochemistry revealed that PPL was strongly expressed in bronchial and alveolar epithelium, but that PPL exhibited changes in intracellular localization among normal and fibrotic alveolar epithelium. In an alveolar epithelial wound repair assay, an anti-PPL IgG decreased cell migration. Recombinant PPL induced bronchoalveolar lavage T lymphocyte proliferation. Patients with IPF with anti-PPL Abs had a more severe respiratory disease, despite no difference in survival.

CONCLUSIONS

We found a new circulating autoAb directed against PPL in patients with IPF, associated with a more severe disease.

Pathogenesis of pulmonary fibrosis in systemic sclerosis: lessons from interstitial lung disease

Interstitial lung disease is a frequent complication of systemic sclerosis and currently is the leading cause of death. Our ability to predict which individuals are at greatest risk of developing clinically significant, progressive interstitial lung disease remains inadequate. Identification of circulating autoantibodies and other biomarkers, as well as genetic polymorphisms and aberrant gene expression, all hold promise as diagnostic and prognostic tools, as well as therapeutic targets. Many practice patterns for the diagnosis and monitoring of connective tissue disease-associated interstitial lung disease are based upon published experience with idiopathic interstitial lung diseases. Although there are likely commonalities in the pathophysiologic mechanisms and clinical progression among all fibrosing lung diseases, a better understanding of features unique to systemic sclerosis-associated interstitial lung disease is essential to the development of more effective monitoring and treatment strategies.

Combined Tlr2 and Tlr4 deficiency increases radiation-induced pulmonary fibrosis in mice

PURPOSE

To determine whether Toll-like receptor 2 or 4 genotype alters the lung response to irradiation in C57BL/6 mice using a model developing a phenotype that resembles radiotherapy-induced fibrosis in both histological characteristics and onset post-treatment.

METHODS AND MATERIALS

The pulmonary phenotype of C57BL/6 mice deficient in each or both of these genes was assessed after an 18-Gy single dose to the thoracic cavity by survival time postirradiation, bronchoalveolar lavage cell differential, histological evidence of alveolitis and fibrosis, and gene expression levels, and compared with that of wild-type mice.

RESULTS

The lung phenotype of Tlr4-deficient and Tlr2-deficient mice did not differ from that of wild-type mice in terms of survival time postirradiation, or by histological evidence of alveolitis or fibrosis. In contrast, mice deficient in both receptors developed respiratory distress at an earlier time than did wild-type mice and presented an enhanced fibrotic response (13.5% vs. 5.8% of the lung by image analysis of histological sections, p < 0.001). No differences in bronchoalveolar cell differential counts, nor in numbers of apoptotic cells in the lung as detected through active caspase-3 staining, were evident among the irradiated mice grouped by Tlr genotype. Gene expression analysis of lung tissue revealed that Tlr2,4-deficient mice have increased levels of hyaluronidase 2 compared with both wild-type mice and mice lacking either Tlr2 or Tlr4.

CONCLUSION

We conclude that a combined deficiency in both Tlr2 and Tlr4, but not Tlr2 or Tlr4 alone, leads to enhanced radiation-induced fibrosis in the C57BL/6 mouse model.

Endothelin in pulmonary fibrosis

The endothelin receptor-ligand system includes a family of polypeptides and G-protein-coupled receptors, which, in addition to their classic activity in the regulation of vascular tone (both directly and through the control of nitric oxide), were implicated in a wide variety of other key biological processes. In this regard, the endothelins are potent mitogens and motogens for mesenchymal cells, and can induce cell differentiation, increasing both the synthesis and deposition of extracellular matrix components and contractile ability. The endothelins are produced as inactive pre-pro-polypeptides, with gene transcription (as well as the proteolytic processing to mature active forms) under the influence of many factors, including cytokines, hypoxia, biomechanical and shear stress, pathogen products, and many growth factors. These complex regulatory events underlie the association and potential role of endothelins in a number of human diseases affecting many different target organs, including the vasculature (atherosclerosis and hypertension), kidney (renal crisis and chronic kidney disease), heart (coronary heart disease), and lungs (pulmonary fibrosis and pulmonary hypertension). This review focuses on the biochemistry of endothelin and the pathobiology of endothelin in lung fibrosis, with particular emphasis on idiopathic pulmonary fibrosis, and examines the antifibrotic potential of endothelin receptor antagonism.

A role for dendritic cells in bleomycin-induced pulmonary fibrosis in mice?

RATIONALE

Lung dendritic cells (DCs) have been shown to accumulate in human fibrotic lung disease, but little is known concerning a role for DCs in the pathogenesis of fibrotic lung.

OBJECTIVES

To characterize lung DCs in an in vivo model of bleomycin-induced pulmonary fibrosis in mice.

METHODS

We characterized the kinetics and activation of pulmonary DCs during the course of bleomycin-induced lung injury by flow cytometry on lung single-cell suspensions. We also characterized the lymphocytes accumulating in bleomycin lung and the chemokines susceptible to favor the recruitment of immune cells.

MEASUREMENTS AND MAIN RESULTS

We show, for the first time, that increased numbers of CD11c(+)/major histocompatibility complex class II(+) DCs, including CD11b(hi) monocyte-derived inflammatory DCs, infiltrate the lung of treated animals during the fibrotic phase of the response to bleomycin. These DCs are mature DCs expressing CD40, CD86, and CD83. They are associated with increased numbers of recently activated memory T cells expressing CD44, CD40L, and CD28, suggesting that fully mature DCs and Ag-experienced T cells can drive an efficient effector immune response within bleomycin lung. Most importantly, when DCs are inactivated with VAG539, a recently described new immunomodulator, VAG539 treatment attenuates the hallmarks of bleomycin lung injury.

CONCLUSIONS

These findings identify lung DCs as key proinflammatory cells potentially able to sustain pulmonary inflammation and fibrosis in the bleomycin model.

CD28 down-regulation on circulating CD4 T-cells is associated with poor prognoses of patients with idiopathic pulmonary fibrosis

Background

Although the etiology of idiopathic pulmonary fibrosis (IPF) remains perplexing, adaptive immune activation is evident among many afflicted patients. Repeated cycles of antigen-induced proliferation cause T-cells to lose surface expression of CD28, and we hypothesized this process might also occur in IPF.

Methodology/Principal Findings

Peripheral blood CD4 T-cells from 89 IPF patients were analyzed by flow cytometry and cytokine multiplex assays, and correlated with clinical events. In comparison to autologous CD4⁺CD28⁺cells, the unusual CD4⁺CD28^null lymphocytes seen in many IPF patients had discordant expressions of activation markers, more frequently produced cytotoxic mediators perforin (2.4±0.8% vs. 60.0±7.4%, p<0.0001) and granzyme B (4.5±2.8% vs.74.9±6.5%, p<0.0001), produced greater amounts of many pro-inflammatory cytokines, and less frequently expressed the regulatory T-cell marker FoxP3 (12.9±1.1% vs. 3.3±0.6% p<0.0001). Infiltration of CD4⁺CD28^null T-cells in IPF lungs was confirmed by confocal microscopy. Interval changes of CD28 expression among subjects who had replicate studies were correlated with conterminous changes of their forced vital capacities (r_s = 0.49, p = 0.012). Most importantly, one-year freedom from major adverse clinical events (either death or lung transplantation) was 56±6% among 78 IPF patients with CD4⁺CD28⁺/CD4_total≥82%, compared to 9±9% among those with more extensive CD28 down-regulation (CD4⁺CD28⁺/CD4_total<82%) (p = 0.0004). The odds ratio for major adverse events among those with the most extensive CD28 down-regulation was 13.0, with 95% confidence intervals 1.6-111.1.

Conclusions/Significance

Marked down-regulation of CD28 on circulating CD4 T-cells, a result of repeated antigen-driven proliferations, is associated with poor outcomes in IPF patients. The CD4⁺CD28^null cells of these patients have potentially enhanced pathogenic characteristics, including increased productions of cytotoxic mediators and pro-inflammatory cytokines. These findings show proliferative T-cell responses to antigen(s) resulting in CD28 down-regulation are associated with progression and manifestations of IPF, and suggest assays of circulating CD4 T-cells may identify patients at greatest risk for clinical deterioration.

Geoepidemiology of COPD and idiopathic pulmonary fibrosis

Progress in improving patient outcomes and advancing therapeutics in chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) is hampered by phenotypic heterogeneity and variable responsiveness to clinical interventions that are not fully explained by currently held disease paradigms for COPD and IPF. Although these chronic lung diseases differ in their geoepidemiology and immunopathogenesis, emerging evidence suggest that organ-specific autoimmunity may underlie subphenotypes of COPD and IPF. In particular, the links to tobacco smoking, diet, gender, and environment are explored in this review. We also highlight potential mechanisms that could guide future investigations in both laboratory and clinical settings. A paradigm shift is needed in how we think about COPD and IPF, based on geoepidemiology and a broader understanding of disease pathogenesis that may ultimately lead to new therapies and improved patient outcomes.

Identification of an autoantigen demonstrates a link between interstitial lung disease and a defect in central tolerance

Interstitial lung disease (ILD) is a common manifestation of systemic autoimmunity characterized by progressive inflammation or scarring of the lungs. Patients who develop these complications can exhibit significantly impaired gas exchange that may result in hypoxemia, pulmonary hypertension, and even death. Unfortunately, little is understood about how these diseases arise, including the role of specific defects in immune tolerance. Another key question is whether autoimmune responses targeting the lung parenchyma are critical to ILD pathogenesis, including that of isolated idiopathic forms. We show that a specific defect in central tolerance brought about by mutations in the autoimmune regulator gene (Aire) leads to an autoreactive T cell response to a lung antigen named vomeromodulin and the development of ILD. We found that a human patient and mice with defects in Aire develop similar lung pathology, demonstrating that the AIRE-deficient model of autoimmunity is a suitable translational system in which to unravel fundamental mechanisms of ILD pathogenesis.

Global impairment of CD4+CD25+FOXP3+ regulatory T cells in idiopathic pulmonary fibrosis

RATIONALE

The implication of T cells in the pathogenesis of idiopathic pulmonary fibrosis (IPF) is controversial. CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) are pivotal in maintaining immune homeostasis, but their role in IPF pathophysiology has not yet been studied.

OBJECTIVES

To explore Treg dynamics and function in IPF.

METHODS

Treg levels and dynamics were analyzed by flow cytometry in the peripheral blood (PB) and bronchoalveolar lavage (BAL) of 21 patients with IPF, 35 patients with lung diseases other than IPF (patients without IPF), 20 patients with collagen vascular diseases with pulmonary parenchymal involvement (CVD-IP), and 28 healthy volunteers. The suppression of autologous CD4(+)CD25(-) cell-proliferative responses and cytokine release by magnetic bead-isolated Tregs was evaluated by proliferation assays and cytometric bead array. Correlations of Treg function and levels with lung function parameters were also performed.

MEASUREMENTS AND MAIN RESULTS

In patients with IPF, both BAL and PB Tregs were reduced compared with those of healthy volunteers and patients without IPF, although not always significantly. Treg levels were not affected by the administration of low-dose prednisone in four nonresponding patients. The suppressor potential of BAL and PB Tregs was compromised in patients with IPF and patients with CVD-IP, compared with healthy volunteers and patients without IPF. Similarly, the Treg-induced suppression of helper T-cell type 1 and 2 cytokine secretion was impaired in the BAL of patients with IPF and patients with CVD-IP. Moreover, the defective function of BAL Tregs correlated highly with parameters of disease severity.

CONCLUSIONS

This study provides the first evidence of global Treg impairment in IPF that strongly correlates with disease severity, suggesting a role for Tregs in the fibrotic process.

Role of T-lymphocytes and pro-inflammatory mediators in the pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the US and a major worldwide healthcare problem. The pathophysiologic mechanisms that drive development and progression of this disease are complex and only poorly understood. While tobacco smoking is the primary risk factor, other disease processes also appear to play a role. Components of the innate immune system (eg, macrophages and neutrophils) have long been believed to be important in the development of COPD. More recent evidence also suggests involvement of the adaptive immune system in pathogenesis of this disease. Here we will review the literature supporting the participation of T-cells in the development of COPD, and comment on the potential antigenic stimuli that may account for these responses. We will further explore the prospective contributions of T-cell derived mediators that could contribute to the inflammation, alveolar wall destruction, and small airway fibrosis of advanced COPD. A better understanding of these complex immune processes will lead to new insights that could result in improved preventative and/or treatment strategies.

Naringenin: a potential immunomodulator for inhibiting lung fibrosis and metastasis

Patients with idiopathic pulmonary fibrosis have a high incidence of lung cancer and a worse prognosis for clinical treatment. A few molecules with antifibrosis properties have been shown promoting cancer progression in clinical trials. The objective of this study was to determine whether there is a similar tendency in mice as in human beings and whether these mice models may be used to find new therapeutic agents with antifibrotic properties but not cancer-promoting properties. We used bleomycin to induce pulmonary fibrosis in mice with or without naringenin treatment and measured the immune-associated lymphocytes and their secreted cytokines using flow cytometry and ELISA from lung tissue. Both passive and spontaneous metastatic models in bleomycin-treated C57BL/6 and BALB/c mice were used to test the hypothesis that mice with pulmonary fibrosis could have an increased risk of lung cancer and associated cancer progression. Here, we show that mice with lung fibrosis challenged using tumors show an increased incidence of lung metastasis and shorter life spans compared with the mice without lung fibrosis. A fibrotic environment in the lung results in increased abundance of transforming growth factor-beta1 and CD4(+)CD25(+)Foxp3(+) regulatory T cells and a decreased proportion of activated effector T cells. This grave immunosuppressive environment favors tumor localization and growth. Naringenin significantly reduces lung metastases in mice with pulmonary fibrosis and increases their survival by improving the immunosuppressive environment through down-regulating transforming growth factor-beta1 and reducing regulatory T cells. Naringenin could be an ideal therapeutic agent in the treatment of both cancer and fibrosis.

New perspectives in the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most frequent idiopathic interstitial pneumonia with a prevalence ranging from 5 to 15 per 100,000 persons, and above 175 per 100,000 in the older population. IPF is a relentlessly progressive fibrotic lung disorder leading to death within a median duration of 3 years. It was hypothesized in the 1970s that pulmonary fibrosis initiates as an "alveolitis" progressing to interstitial fibrosis with connective tissue deposition, derangement of the lung architecture and functional impairment. However, in vitro studies indicated that alveolar/bronchiolar injured epithelial cells can drive the fibrotic process in the absence of macrophages and with minimal inflammation. This, together with the inability of classic immunosuppressive therapy to cure IPF, generated new pathogenesis paradigms and intense research into the role of the lack or the excessive production of anti-fibrotic or profibrotic mediators, oxidant injury, exaggerated coagulation, thus leading to investigate new treatment strategies. Preliminary results of some of such trials have shown significant reductions in lung function decline, disease exacerbation and mortality.

T cells, B cells, and polarized immune response in the pathogenesis of fibrosis and systemic sclerosis

PURPOSE OF REVIEW

A better comprehension of the interactions between cells of the adaptive immune system with fibroblasts and endothelial cells is required to understand abnormal extracellular matrix deposition, development of pathologic fibrosis, and vasculopathy.

RECENT FINDINGS

Skin T cells with high IL-4 production potential and peripheral blood T cells preferentially expressing chemokine receptors associated with Th2 functions are found in individuals with active systemic sclerosis. Animal models indicate that Th2 cells and IL-13 can induce muscular hypertrophy in pulmonary arterial vasculature. In bleomycin-induced fibrosis, B cells produce fibrogenic cytokines upon interaction of an endogenous ligand (hyaluronan) with toll-like receptor-4. In the sclerodermatous graft versus host model, the lack of tumor necrosis factor-production by CD4+ T cells is permissive for fibrosis development. Dermal fibrosis and capillary loss typical of systemic sclerosis can be reversible after high-dose immunosuppression and hematopoietic stem cell transplantation.

SUMMARY

Although immunosuppressive strategies to treat patients with systemic sclerosis and allied conditions are largely disappointing, thus indicating a permissive rather than causative role of immunoinflammatory events characteristic of the disease, new findings stress that cells of the adaptive immune system play important roles in assisting fibrogenesis and vascular abnormalities. This may help in identifying efficacious strategies aimed at their control.

The pro-fibrotic factor IGFBP-5 induces lung fibroblast and mononuclear cell migration

We have previously shown that insulin-like growth factor-binding protein-5 (IGFBP-5) is overexpressed in fibrotic lung tissues and that it induces production of extracellular matrix components such as collagen and fibronectin both in vitro and in vivo. We recently observed mononuclear cell infiltration in lung tissues of mice expressing IGFBP-5. We therefore examined the role of IGFBP-5 on the migration of immune cells. Migration assays demonstrated that IGFBP-5 induced migration of peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner. Preferential migration of monocytes/macrophages, natural killer cells, and T cells was observed. Moreover, the CD4/CD8 ratio of migrating cells was significantly higher in vitro and in vivo in response to IGFBP-5. IGFBP-5 resulted in preferential migration of activated CD4(+) T cells and monocytes. Interestingly, IGFBP-5 also induced migration of primary human lung fibroblasts. Exogenous administration of IGFBP-5 induced activation of mitogen-activated protein kinase (MAPK) signaling cascade but not PI3K in PBMCs. IGFBP-5-induced migration was blocked by the MEK1/2 inhibitor U0126, suggesting that IGFBP-5-induced migration occurs via MAPK activation. Furthermore, monocytes treated with recombinant IGFBP-5 expressed the mesenchymal markers alpha-smooth muscle actin and fibronectin in vitro and in vivo, suggesting that IGFBP-5 can induce the transformation of monocytes into mesenchymal cells. Collectively, our results suggest that IGFBP-5 induces cell migration via MAPK-dependent and IGF-I-independent mechanisms.