Farmer's lung. Long-term outcome and lack of predictive value of bronchoalveolar lavage fibrosing factors

Hypersensitivity Pneumonitis: Challenges of a Complex Disease

Hypersensitivity pneumonitis (HP) is a complex interstitial lung disease caused by chronic inhalation of a wide variety of antigens in susceptible and sensitized individuals, commonly associated with an occupational exposure. An impressive number of inciting antigens causing hypersensitivity pneumonitis have been found to cover a wide range of occupations. As working practices have changed over time, especially in industrialized countries, new names for occupational HP have emerged. This review emphasizes the main diagnostic issues arising from the high variability of clinical presentation and the broad spectrum of causal antigens. Furthermore, it provides an overview of current methods to unveil possible causes of hypersensitivity pneumonitis, highlights HP's current diagnostic and treatment challenges and the remaining areas of uncertainty, and presents prevention strategies.

High-Resolution Computed Tomography of Fibrotic Interstitial Lung Disease

While radiography is the first-line imaging technique for evaluation of pulmonary disease, high-resolution computed tomography (HRCT) provides detailed assessment of the lung parenchyma and interstitium, allowing normal anatomy to be differentiated from superimposed abnormal findings. The fibrotic interstitial lung diseases have HRCT features that include reticulation, traction bronchiectasis and bronchiolectasis, honeycombing, architectural distortion, and volume loss. The characterization and distribution of these features result in distinctive CT patterns. The CT pattern and its progression over time can be combined with clinical, serologic, and pathologic data during multidisciplinary discussion to establish a clinical diagnosis. Serial examinations identify progression, treatment response, complications, and can assist in determining prognosis. This article will describe the technique used to perform HRCT, the normal and abnormal appearance of the lung on HRCT, and the CT patterns identified in common fibrotic lung diseases.

Assessment and Management of Occupational Hypersensitivity Pneumonitis

The diagnosis and treatment of occupational hypersensitivity pneumonitis (OHP) remain complex and challenging in the absence of diagnostic gold standards or clinical guidelines. This review provides an update of the recent literature regarding the different presentations of OHP and the diagnostic yield and value of the diagnostic tests currently available, which include occupational and medical history, laboratory tests (serum-specific immunoglobulins, environmental sampling), imaging, bronchoalveolar lavage, transbronchial biopsy, transbronchial cryobiopsy, surgical lung biopsy, and specific inhalation challenges. These tools provide a precise differential diagnosis within the framework of interstitial lung diseases. However, among the chronic fibrotic forms, distinguishing OHP from sarcoidosis, nonspecific interstitial pneumonia and idiopathic pulmonary fibrosis remains a diagnostic challenge. Avoidance of exposure is pivotal for OHP management, whereas corticosteroids are fundamental in the pharmacological approach to this disease. In addition, studies describing the long-term benefits of immunosuppressive and antifibrotic agents have increased the use of these treatments in OHP.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of a variety of antigens in susceptible and sensitized individuals. These antigens are found in the environment, mostly derived from bird proteins and fungi. The prevalence and incidence of HP vary widely depending on the intensity of exposure, the geographical area and the local climate. Immunopathologically, HP is characterized by an exaggerated humoral and cellular immune response affecting the small airways and lung parenchyma. A complex interplay of genetic, host and environmental factors underlies the development and progression of HP. HP can be classified into acute, chronic non-fibrotic and chronic fibrotic forms. Acute HP results from intermittent, high-level exposure to the inducing antigen, usually within a few hours of exposure, whereas chronic HP mostly originates from long-term, low-level exposure (usually to birds or moulds in the home), is not easy to define in terms of time, and may occur within weeks, months or even years of exposure. Some patients with fibrotic HP may evolve to a progressive phenotype, even with complete exposure avoidance. Diagnosis is based on an accurate exposure history, clinical presentation, characteristic high-resolution CT findings, specific IgG antibodies to the offending antigen, bronchoalveolar lavage and pathological features. Complete antigen avoidance is the mainstay of treatment. The pharmacotherapy of chronic HP consists of immunosuppressive drugs such as corticosteroids, with antifibrotic therapy being a potential therapy for patients with progressive disease.

Diagnosis of Hypersensitivity Pneumonitis in Adults. An Official ATS/JRS/ALAT Clinical Practice Guideline

Background: This guideline addresses the diagnosis of hypersensitivity pneumonitis (HP). It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax.Methods: Systematic reviews were performed for six questions. The evidence was discussed, and then recommendations were formulated by a multidisciplinary committee of experts in the field of interstitial lung disease and HP using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach.Results: The guideline committee defined HP, and clinical, radiographic, and pathological features were described. HP was classified into nonfibrotic and fibrotic phenotypes. There was limited evidence that was directly applicable to all questions. The need for a thorough history and a validated questionnaire to identify potential exposures was agreed on. Serum IgG testing against potential antigens associated with HP was suggested to identify potential exposures. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. For patients with fibrotic HP, suggestions were made in favor of obtaining BAL for lymphocyte cellular analysis, transbronchial lung cryobiopsy, and surgical lung biopsy. Diagnostic criteria were established, and a diagnostic algorithm was created by expert consensus. Knowledge gaps were identified as future research directions.Conclusions: The guideline committee developed a systematic approach to the diagnosis of HP. The approach should be reevaluated as new evidence accumulates.

Mechanisms of exercise limitation in patients with chronic hypersensitivity pneumonitis

Small airway and interstitial pulmonary involvements are prominent in chronic hypersensitivity pneumonitis (cHP). However, their roles on exercise limitation and the relationship with functional lung tests have not been studied in detail.

Our aim was to evaluate exercise performance and its determinants in cHP. We evaluated maximal cardiopulmonary exercise testing performance in 28 cHP patients (forced vital capacity 57±17% pred) and 18 healthy controls during cycling.

Patients had reduced exercise performance with lower peak oxygen production (16.6 (12.3–19.98) mL·kg⁻¹·min⁻¹versus 25.1 (16.9–32.0), p=0.003), diminished breathing reserve (% maximal voluntary ventilation) (12 (6.4–34.8)% versus 41 (32.7–50.8)%, p<0.001) and hyperventilation (minute ventilation/carbon dioxide production slope 37±5 versus 31±4, p<0.001). All patients presented oxygen desaturation and augmented Borg dyspnoea scores (8 (5–10) versus 4 (1–7), p=0.004). The prevalence of dynamic hyperinflation was found in only 18% of patients. When comparing cHP patients with normal and low peak oxygen production (<84% pred, lower limit of normal), the latter exhibited a higher minute ventilation/carbon dioxide production slope (39±5.0 versus 34±3.6, p=0.004), lower tidal volume (0.84 (0.78–0.90) L versus 1.15 (0.97–1.67) L, p=0.002), and poorer physical functioning score on the Short form-36 health survey. Receiver operating characteristic curve analysis showed that reduced lung volumes (forced vital capacity %, total lung capacity % and diffusing capacity of the lung for carbon dioxide %) were high predictors of poor exercise capacity.

Reduced exercise capacity was prevalent in patients because of ventilatory limitation and not due to dynamic hyperinflation. Reduced lung volumes were reliable predictors of lower performance during exercise.

Besides significant small airway involvement, reduced exercise capacity is due to ventilatory limitation and not due to dynamic hyperinflation in chronic hypersensitivity pneumonitishttp://ow.ly/Ou9230kSBQz

[The respiratory effects of smoking]

A marked increase in the morbidity and mortality of a large number of broncho-pulmonary diseases has been documented in relation to smoking. The influence of tobacco smoking on various respiratory conditions. is discussed: incidence, severity or natural history modification of some respiratory illnesses: obstructive lung diseases (COPD, asthma), lung cancer, bacterial, viral respiratory infections, with the impact of smoking on tuberculosis. Finally, the relationship of tobacco with diffuse interstitial lung disease: protective role of smoking (controversial in sarcoidosis, real in hypersensitivity pneumonitis). The benefits of smoking cessation are described.

Current and emerging techniques for the diagnosis of hypersensitivity pneumonitis

INTRODUCTION

Hypersensitivity pneumonitis (HP) is the result of an immunologically induced inflammation of the lung parenchyma in response to inhalation exposure to a large variety of antigens in genetically susceptible individuals. HP shares clinical and radiological features with other acute and chronic interstitial lung diseases and is sometimes difficult to diagnose if exposure to an antigenic agent is not detected. Several classifications and diagnostic criteria have been proposed but are not currently recommended by guidelines from any scientific society. However, advances have been made over the past ten years in improving the diagnosis of HP. Areas covered: This article will provide a summary of the different classification and diagnostic criteria proposed in acute and chronic forms of HP. In addition, we review current diagnostic procedures including antigen detection, high resolution computed tomography, histopathology and provide an overview of emerging techniques. Expert commentary: Important changes are occurring in the field of HP and knowledge of the disease will likely progress enormously in the coming 5 to 10 years as many techniques continue to be developed, including genomic signature and diagnostic biomarkers.

Functional associations of pleuroparenchymal fibroelastosis and emphysema with hypersensitivity pneumonitis

BACKGROUND

Pleuroparenchymal fibroelastosis (PPFE) has been described in hypersensitivity pneumonitis (HP) yet its functional implications are unclear. Combined pulmonary fibrosis and emphysema (CPFE) has occasionally been described in never-smokers with HP, but epidemiological data regarding its prevalence is sparse. CTs in a large HP cohort were therefore examined to identify the prevalence and effects of PPFE and emphysema.

Methods

233 HP patients had CT extents of interstitial lung disease (ILD) and emphysema quantified to the nearest 5%. Lobar percentage pleural involvement of PPFE was quantified on a 4-point categorical scale: 0 = absent, 1 = affecting <10%, 2 = affecting 10–33%, 3 = affecting >33%. Marked PPFE reflected a total lung score of ≥3/18. Results were evaluated against FVC, DLco and mortality.

RESULTS

Marked PPFE prevalence was 23% whilst 23% of never-smokers had emphysema. Following adjustment for patient age, gender, smoking status, and ILD and emphysema extents, marked PPFE independently linked to reduced baseline FVC (p = 0.0002) and DLco (p = 0.002) and when examined alongside the same covariates, independently linked to worsened survival (p = 0.01).

CPFE in HP demonstrated a characteristic functional profile of artificial lung volume preservation and disproportionate DLco reduction. CPFE did not demonstrate a worsened outcome when compared to HP patients without emphysema beyond that explained by CT extents of ILD and emphysema.

CONCLUSIONS

PPFE is not uncommon in HP, and is independently associated with impaired lung function and increased mortality. Emphysema was identified in 23% of HP never-smokers. CPFE appears not to link to a malignant microvascular phenotype as outcome is explained by ILD and emphysema extents.

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In patients with HP, marked PPFE had a prevalence of 23% in our study cohort.

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23% of never-smokers with HP demonstrated emphysema on CT imaging.

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Outcome in HP patients with CPFE is explained by CT extents of ILD and emphysema.

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PPFE is independently associated with a worsened outcome in HP.

Emphysematous changes in hypersensitivity pneumonitis: A retrospective analysis of 12 patients

Introduction

Emphysema is most commonly associated with smoking but also occurs in hypersensitivity pneumonitis (HP). The aim of this study was to further explore this relationship.

Methods

A retrospective, computer-assisted search was performed to identify patients with HP seen at Mayo Clinic in Rochester, Minnesota, from January 1997 through February 2014. Demographic, clinical, and imaging features were analyzed. Patients were excluded if they had a smoking history of 10 pack-years or more.

Results

Twelve patients (9 males) with HP and computed tomographic evidence of emphysema were identified. Ten were never smokers and 2 were ex-smokers. The median age at diagnosis was 47 (range, 29-77) years; median symptom duration was 2.2 (range, 0.2-13.4) years. The most common presenting symptoms were dyspnea (83%) and cough (67%). On pulmonary function testing, 6 patients (50%) had a restrictive defect, 2 (17%) had airflow obstruction, and 4 (33%) had an isolated reduction in diffusing capacity of lung for carbon monoxide. The severity of emphysema ranged from mild to severe to focal bullae. All patients had chronic hypersensitivity pneumonitis (CHP). Centrilobular emphysema was most commonly seen with coexistent paraseptal emphysema in 5 patients.Emphysema was most frequent in the upper lung but could be seen in any lobe.

Conclusion

Emphysema can occur in patients with CHP independently of smoking history and exposure to specific types of antigens. Emphysematous changes seem to progress at a slower pace compare to reticulations/fibrosis.

The MUC5B promoter polymorphism and telomere length in patients with chronic hypersensitivity pneumonitis: an observational cohort-control study

BACKGROUND

Patients with hypersensitivity pneumonitis are at risk of developing pulmonary fibrosis, which is associated with reduced survival. In families with multiple affected members, individuals might be diagnosed as having idiopathic pulmonary fibrosis (IPF) or chronic (fibrotic) hypersensitivity pneumonitis, which suggests these disorders share risk factors. We aimed to test whether the genomic risk factors associated with the development and progression of IPF are also associated with the development of fibrosis and reduced survival in people with chronic hypersensitivity pneumonitis.

METHODS

We did an observational study of two independent cohorts of patients with chronic hypersensitivity pneumonitis, one from the University of California San Francisco, CA, USA (UCSF), and one from the University of Texas Southwestern, TX, USA (UTSW). We measured two common single-nucleotide polymorphisms associated with IPF (MUC5B rs35705950 and TOLLIP rs5743890) and telomere length in peripheral blood leucocytes, and assessed their associations with chronic hypersensitivity pneumonitis risk, survival, and clinical, radiographic, and pathological features. We compared findings with those in patients with IPF from the UCSF and UTSW cohorts, and healthy controls from the European population of the 1000 Genomes Project Phase 3, version 1.

FINDINGS

The cohorts included 145 patients from UCSF and 72 from UTSW. The minor allele frequency (MAF) was greater for MUC5B rs35705950 in patients with chronic hypersensitivity pneumonitis than in healthy controls (24·4% in UCSF and 32·3% in UTSW vs 10·7%, both p<0·0001), but not for TOLLIP rs5743890. The MAFs were similar to those for IPF (UCSF 33·3%, p=0·09; UTSW 32·0%, p=0·95). In the combined UCSF and UTSW chronic hypersensitivity pneumonitis cohort, we saw associations between extent of radiographic fibrosis and MUC5B rs35705950 minor alleles (adjusted odds ratio [OR] 1·91, 95% CI 1·02-3·59, p=0·045) and short telomere length (adjusted OR per unit change in mean natural logarithm-transformed ratio of telomere repeat copy number to single gene copy number 0·23, 0·09-0·59, p=0·002). Telomere length less than the tenth percentile for age was also significantly associated with reduced survival (log-rank p=0·006).

INTERPRETATION

The associations between MUC5B rs35705950 and short telomere length with extent of fibrosis, histopathological features of usual interstitial pneumonia, and reduced survival in patients with chronic hypersensitivity pneumonitis suggest shared pathobiology with IPF, and might help to stratify risk.

FUNDING

National Institutes of Health and Nina Ireland Program for Lung Health.

Emphysema in active farmer's lung disease

BACKGROUND

Farmer's lung (FL) is a common type of hypersensitivity pneumonitis. It is often considered that fibrosis is the most frequent finding in chronic FL. Nevertheless, three cohort studies have suggested that some patients with chronic FL may develop emphysema. We aimed to evaluate the current prevalence of emphysema in active FL, to describe the radiological and functional features of emphysema in active FL, and to identify risk factors associated with emphysema in this population.

METHODS

Patients aged over 18 years with active FL were prospectively recruited through the SOPHIA study (CPP Est; P-2009-521), between 2007 and 2015. Each patient had complete medical history screening, clinical examination, high resolution computed tomodensitometry, bronchoalveolar lavage, pulmonary function tests and serum precipitins.

RESULTS

Among 33 patients with active FL, the prevalence of emphysema in this series of incident active FL cases was higher (48.5%) than that of fibrosis (12%) and was not dependent on smoking habits. Most patients with emphysema did not have lung hyperinflation. The possible risk factors for emphysema in active FL were a longer duration of exposure to organic dusts, and at a higher level.

CONCLUSION

Emphysema is found in half of patients with active FL and may be influenced by exposure patterns.

Respiratory Allergic Disorders

Allergic asthma refers to a chronic reversible bronchoconstriction influenced by an allergic trigger, leading to symptoms of cough, wheezing, shortness of breath, and chest tightness. Allergic bronchopulmonary aspergillosis is a complex hypersensitivity reaction, often in patients with asthma or cystic fibrosis, occurring when bronchi become colonized by Aspergillus species. The clinical picture is dominated by asthma complicated by recurrent episodes of bronchial obstruction, fever, malaise, mucus production, and peripheral blood eosinophilia. Hypersensitivity pneumonitis is a syndrome associated with lung inflammation from the inhalation of airborne antigens, such as molds and dust.

Elevated levels of FN1 and CCL2 in bronchoalveolar lavage fluid from sarcoidosis patients

Background

Sarcoidosis is a granulomatous systemic inflammatory disease in which more than 90 % of all patients develop pulmonary manifestations. Several gene associations have previously been described, but established and clinically useful biomarkers are still absent. This study aimed to find proteins in bronchoalveolar lavage (BAL) fluid that can be associated with the disease.

Methods

We developed and performed profiling of 94 selected proteins in BAL fluid and serum samples obtained from newly diagnosed and non-treated patients with sarcoidosis. Using multiplexed immunoassays, a total of 317 BAL and 217 serum samples were analyzed, including asthmatic patients and healthy individuals as controls.

Results

Our analyses revealed increased levels of eight proteins in sarcoidosis patients compared to controls. Out of these, fibronectin (FN1) and C-C motif chemokine 2 (CCL2) revealed the strongest associations. In addition, cadherin 5 (CDH5) was found to correlate positively with lymphocyte cell numbers in BAL fluid.

Conclusions

Applying a high throughput proteomics screening technique, we found proteins of potential clinical relevance in the context of sarcoidosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0381-0) contains supplementary material, which is available to authorized users.

Occupational hypersensitivity pneumonitis: an EAACI position paper

The aim of this document was to provide a critical review of the current knowledge on hypersensitivity pneumonitis caused by the occupational environment and to propose practical guidance for the diagnosis and management of this condition. Occupational hypersensitivity pneumonitis (OHP) is an immunologic lung disease resulting from lymphocytic and frequently granulomatous inflammation of the peripheral airways, alveoli, and surrounding interstitial tissue which develops as the result of a non-IgE-mediated allergic reaction to a variety of organic materials or low molecular weight agents that are present in the workplace. The offending agents can be classified into six broad categories that include bacteria, fungi, animal proteins, plant proteins, low molecular weight chemicals, and metals. The diagnosis of OHP requires a multidisciplinary approach and relies on a combination of diagnostic tests to ascertain the work relatedness of the disease. Both the clinical and the occupational history are keys to the diagnosis and often will lead to the initial suspicion. Diagnostic criteria adapted to OHP are proposed. The cornerstone of treatment is early removal from exposure to the eliciting antigen, although the disease may show an adverse outcome even after avoidance of exposure to the causal agent.

Lymphangiogenic factors are associated with the severity of hypersensitivity pneumonitis

Background

Antigen presenting cells play a pivotal role in the adaptive immune response in hypersensitivity pneumonitis (HP). It was hypothesised that lymphangiogenesis is involved in the pathophysiology of HP via cell transport.

Objective

To determine the clinical significance of lymphangiogenic factors in HP.

Methods

Levels of vascular endothelial growth factors (VEGF)-A, VEGF-C, VEGF-D and CCL21 in the serum and bronchoalveolar lavage fluid (BALF) were measured in 29 healthy volunteers, 14 patients with idiopathic pulmonary fibrosis (IPF) and 26 patients with HP by ELISA. Additionally, immunohistochemical analyses were performed using lung specimens of patients with HP (n=8) and IPF (n=10).

Results

BALF VEGF-D levels were significantly elevated in patients with HP compared to the other groups. BALF VEGF–D levels in patients with HP correlated significantly with the BALF total cell and lymphocyte counts (r=0.485, p=0.014 and r=0.717, p<0.0001, respectively). BALF VEGF-C and CCL21 levels were increased in patients with HP compared to healthy volunteers, but not patients with IPF. BALF CCL21 levels were negatively correlated with the forced expiratory volume in 1 s percentage and diffuse capacity of the lung for carbon monoxide (r=−0.662, p=0.007 and r=−0.671, p=0.024, respectively). According to the immunohistochemical analyses, CCL21 was expressed in the lymphatic endothelium in both conditions and CCR7⁺ cells were aggregated around lymphatics in patients with HP, but not in patients with IPF.

Conclusions

Lymphangiogenic factors might be associated with the inflammatory and functional severity of HP. The increased BALF VEGF-D levels were associated with lymphatic alveolitis intensity, and CCL21 with lung function impairment.

Identifying an inciting antigen is associated with improved survival in patients with chronic hypersensitivity pneumonitis

BACKGROUND

The cornerstone of hypersensitivity pneumonitis (HP) management is having patients avoid the inciting antigen (IA). Often, despite an exhaustive search, an IA cannot be found. The objective of this study was to examine whether identifying the IA impacts survival in patients with chronic HP.

METHODS

We used the Kaplan-Meier method to display, and the log-rank test to compare, survival curves of patients with well-characterized chronic HP stratified on identification of an IA exposure. A Cox proportional hazards (PH) model was used to identify independent predictors in time-to-death analysis.

RESULTS

Of 142 patients, 67 (47%) had an identified IA, and 75 (53%) had an unidentified IA. Compared with survivors, patients who died (n = 80, 56%) were older, more likely to have smoked, had lower total lung capacity % predicted and FVC % predicted, had higher severity of dyspnea, were more likely to have pulmonary fibrosis, and were less likely to have an identifiable IA. In a Cox PH model, the inability to identify an IA (hazard ratio [HR], 1.76; 95% CI, 1.01-3.07), older age (HR, 1.04; 95% CI, 1.01-1.07), the presences of pulmonary fibrosis (HR, 2.43; 95% CI, 1.36-4.35), a lower FVC% (HR, 1.36; 95% CI, 1.10-1.68), and a history of smoking (HR, 2.01; 95% C1, 1.15-3.50) were independent predictors of shorter survival. After adjusting for mean age, presence of fibrosis, mean FVC%, mean diffusing capacity of the lung for carbon monoxide (%), and history of smoking, survival was longer for patients with an identified IA exposure than those with an unidentified IA exposure (median, 8.75 years vs 4.88 years; P = .047).

CONCLUSIONS

Among patients with chronic HP, when adjusting for a number of potentially influential predictors, including the presence of fibrosis, the inability to identify an IA was independently associated with shortened survival.

Other asthma considerations

Asthma is a heterogeneous syndrome of cough, wheeze, dyspnea, and chest tightness. However, in a subset of patients, these symptoms may indicate a different underlying disease process with variable responsiveness to classic asthma therapies. Disease may progress while practitioners attempt conventional asthma therapy. Additionally, some types of asthma may require alternative approaches to relieve symptoms successfully. This article describes the differential diagnosis of asthma and discusses some of the more common asthma variants and asthma mimickers.

Human monocyte-derived dendritic cells exposed to microorganisms involved in hypersensitivity pneumonitis induce a Th1-polarized immune response

Hypersensitivity pneumonitis (HP) is an immunoallergic disease characterized by a prominent interstitial infiltrate composed predominantly of lymphocytes secreting inflammatory cytokines. Dendritic cells (DCs) are known to play a pivotal role in the lymphocytic response. However, their cross talk with microorganisms that cause HP has yet to be elucidated. This study aimed to investigate the initial interactions between human monocyte-derived DCs (MoDCs) and four microorganisms that are different in nature (Saccharopolyspora rectivirgula [actinomycetes], Mycobacterium immunogenum [mycobacteria], and Wallemia sebi and Eurotium amstelodami [filamentous fungi]) and are involved in HP. Our objectives were to determine the cross talk between MoDCs and HP-causative agents and to determine whether the resulting immune response varied according to the microbial extract tested. The phenotypic activation of MoDCs was measured by the increased expression of costimulatory molecules and levels of cytokines in supernatants. The functional activation of MoDCs was measured by the ability of MoDCs to induce lymphocytic proliferation and differentiation in a mixed lymphocytic reaction (MLR). E. amstelodami-exposed (EA) MoDCs expressed higher percentages of costimulatory molecules than did W. sebi-exposed (WS), S. rectivirgula-exposed (SR), or M. immunogenum-exposed (MI) MoDCs (P < 0.05, Wilcoxon signed-rank test). EA-MoDCs, WS-MoDCs, SR-MoDCs, and MI-MoDCs induced CD4(+) T cell proliferation and a Th1-polarized immune response. The present study provides evidence that, although differences were initially observed between MoDCs exposed to filamentous fungi and MoDCs exposed to bacteria, a Th1 response was ultimately promoted by DCs regardless of the microbial extract tested.

Recent advances in hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a pulmonary disease with symptoms of dyspnea and cough resulting from the inhalation of an allergen to which the subject has been previously sensitized. The diagnosis of HP most often relies on an array of nonspecific clinical symptoms and signs developed in an appropriate setting, with the demonstration of interstitial markings on chest radiographs, serum precipitating antibodies against offending antigens, a lymphocytic alveolitis on BAL, and/or a granulomatous reaction on lung biopsies. The current classification of HP in acute, subacute, and chronic phases is now challenged, and a set of clinical predictors has been proposed. Nonspecific interstitial pneumonitis, usual interstitial pneumonia, and bronchiolitis obliterans organizing pneumonia may be the sole histologic expression of the disease. Presumably, like in idiopathic interstitial pneumonia, acute exacerbations of chronic HP may occur without further exposure to the offending antigen. New offending antigens, such as mycobacteria causing hot tub lung and metalworking fluid HP, have recently been identified and have stimulated further research in HP.

Hypersensitivity pneumonitis

Clinical manifestations of hypersensitivity pneumonitis may closely mimic other interstitial lung diseases, and the disease onset is usually insidious. High-resolution computed tomography and bronchoalveolar lavage are the sensitive and characteristic diagnostic tests for hypersensitivity pneumonitis. The relevant antigen to hypersensitivity pneumonitis cannot be identified in up to 20% to 30% of patients. Clinicians should be aware that hypersensitivity pneumonitis must be considered in all cases of interstitial lung disease, and a detailed environmental exposure history is mandatory.

γδ T cells protect against lung fibrosis via IL-22

Inflammation-induced pulmonary fibrosis (PF) leads to irreversible loss of lung function and is a predictor of mortality in numerous lung diseases. Why some subjects with lung inflammation but not others develop PF is unclear. In a mouse model of hypersensitivity pneumonitis that progresses to lung fibrosis upon repeated exposure to the ubiquitous microorganism Bacillus subtilis, γδ T cells expand in the lung and inhibit collagen deposition. We show that a subset of these γδ cells represents the predominant source of the Th17 cytokine IL-22 in this model. Preventing expression of IL-22, either by mutating the aryl hydrocarbon receptor (AhR) or inhibiting AhR signaling, accelerated lung fibrosis. Direct blockade of IL-22 also enhanced collagen deposition in the lung, whereas administration of recombinant IL-22 inhibited lung fibrosis. Moreover, the presence of protective γδ T cells and IL-22 diminished recruitment of CD4(+) T cells to lung. These data reveal a protective pathway that involves the inhibition of αβ T cells by regulatory IL-22-secreting γδ T cells.

Hypersensitivity pneumonitis

PURPOSE OF REVIEW

To bring readers up to date on recent reports, both clinical and basic understanding, on hypersensitivity pneumonitis.

RECENT FINDINGS

Although many antigens and environmental settings have already been described as sources of this hyperimmune pulmonary disease, the literature continues to bring forth other conditions that can cause hypersensitivity pneumonitis. We also highlight new findings in the diagnosis of hypersensitivity pneumonitis, its histopathology, insight into its potential outcomes, and understanding of its immune mechanisms that could lead to new treatments.

SUMMARY

The review will help clinicians in their diagnostic approach to hypersensitivity pneumonitis and lead them to look for other potential sources of the disease. The findings described will help guide further research on the pathophysiology and seek new treatments for this worldwide orphan disease.

Hypersensitivity pneumonitis: a historical, clinical, and radiologic review

Most cases of hypersensitivity pneumonitis develop only after many years of inhaling allergens, which include microbes, animal or plant proteins, and certain chemicals that form haptens. The initial clinical presentation is either episodes of acute illness with dyspnea and prominent constitutional symptoms, such as fever, or an insidious onset of dyspnea, coughing, and weight loss, sometimes with superimposed acute episodes. The histopathologic process consists of chronic inflammation of the bronchi and peribronchiolar tissue, often with poorly defined granulomas and giant cells in the interstitium or alveoli. Fibrosis and emphysema may develop. The radiologic findings include diffuse ground-glass opacification, centrilobular ground-glass opacities, air trapping, fibrosis, lung cysts, and emphysema. The histologic and radiologic features in some cases may resemble those of usual interstitial pneumonia or nonspecific interstitial pneumonia. The diagnosis usually rests on a variable combination of findings from history, serology, radiography, lung biopsy, and bronchoalveolar lavage, which characteristically reveals a lymphocyte content of more than 30%, often with an increased CD4-to-CD8 ratio of T cells. Treatment includes avoiding the allergen, if possible, and, in severe cases, systemic corticosteroids. The long-term prognosis is usually good, but some patients develop severe respiratory insufficiency, and a few die of the disease.

Gammadelta T cells and Th17 cytokines in hypersensitivity pneumonitis and lung fibrosis

Hypersensitivity pneumonitis (HP) is an inflammatory lung disease caused by the repeated inhalation of aerosolized antigens. With chronic exposure to an inhaled antigen, patients are at risk of developing irreversible pulmonary fibrosis as well as an increased morbidity and mortality. Although alphabeta T cells have been shown to be important in the pathogenesis of HP, gammadelta T cells also accumulate in the bronchoalveolar lavage of patients with HP. gammadelta T cells represent a distinct lymphocyte subset, whose primary function is not well understood. In contrast to alphabeta T cells, gammadelta T cells recognize unprocessed antigens, such as those upregulated on injured or stressed epithelial cells. In a murine model of HP induced by exposure to the ubiquitous microorganism Bacillus subtilis, gammadelta T cells expressing the canonical Vgamma6/Vdelta1 T cell receptor were dramatically expanded in the lung. The predominant cytokines expressed by this gammadelta T-cell subset were T-helper 17 (Th17) cytokines that were critical for bacterial clearance and the resolution of lung inflammation. Th17-expressing gammadelta T cells are also expanded in other murine models of lung infection and inflammation, which suggests that these cells play a sentinel role in mucosal immunity. Thus, an increased understanding of gammadelta T cells that express Th17 cytokines in HP and other inflammatory lung diseases may lead to the development of novel therapeutic and clinical strategies that prevent the development of fibrotic lung disease.

IL-17A-expressing T cells are essential for bacterial clearance in a murine model of hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an inflammatory lung disease characterized by a diffuse mononuclear cell infiltrate in the lung that can progress to pulmonary fibrosis with chronic exposure to an inhaled Ag. We previously reported that C57BL/6 mice repeatedly exposed to the ubiquitous microorganism Bacillus subtilis develop mononuclear infiltrates in the lung that contain Vgamma6/Vdelta1(+) gammadelta T cells. In the absence of this T cell subset, mice treated with B. subtilis had significantly increased collagen deposition in the lung, suggesting a regulatory role for Vgamma6/Vdelta1(+) gammadelta T cells. To further investigate the role of Vgamma6/Vdelta1(+) gammadelta T cells in B. subtilis-induced lung fibrosis, we exposed transgenic Vgamma6/Vdelta1 mice to this microorganism and found decreased collagen content in the lung compared with wild-type C57BL/6 mice. Cytokine analysis of lung homogenates from wild-type C57BL/6 mice demonstrated increased IL-17A concentrations with repeated exposure to B. subtilis. In the absence of IL-17 receptor signaling, IL-17ra(-/-) mice had delayed clearance of B. subtilis with increased lung inflammation and fibrosis. Although IL-17A was predominantly expressed by Vgamma6/Vdelta1(+) T cells, a compensatory increase in IL-17A expression by CD4(+) T cells was seen in the absence of gammadelta T cells that resulted in similar levels of IL-17A in the lungs of TCRdelta(-/-) and wild-type C57BL/6 mice. In combination, our data suggest an important role for IL-17A-expressing T lymphocytes, both gammadelta and alphabeta T cells, in eliminating this microorganism that prevents excessive inflammation and eventual lung fibrosis in this murine model of B. subtilis-induced hypersensitivity pneumonitis.

Hypersensitivity pneumonitis

The first few cases of hypersensitivity pneumonitis (HP) were described in the early 20th century in farmers exposed to moldy hay or straw. As then, HP has been ascribed to multiple inhaled antigens found in a large variety of environmental settings. Hypersensitivity pneumonitis results from an exaggerated immune response, which gives rise to acute infection-like symptoms or to progressive, sometimes irreversible lung damage. The diagnosis is based on a combination of clinical characteristics of the disease. Clinical diagnostic criteria have recently been published. The immune mechanisms leading to HP are still incompletely understood. Initially, believed to be a classes III and IV immune response, we now have a clearer understanding of the complex inflammatory events involved. These include the release of pro inflammatory cytokines and a decrease in the immune control mechanisms via surfactant, dendritic and T-regulatory cells. Despite the improved understanding, the treatment and outcome of HP have not changed. Oral corticosteroids remain the only effective drugs and contact withdrawal constitutes the ideal solution. If unchecked, HP can lead to irreversible lung damage in the form of fibrosis or emphysema, respiratory insufficiency and even death.

Pulmonary fibrosis: pathogenesis, etiology and regulation

Pulmonary fibrosis and architectural remodeling of tissues can severely disrupt lung function, often with fatal consequences. The etiology of pulmonary fibrotic diseases is varied, with an array of triggers including allergens, chemicals, radiation and environmental particles. However, the cause of one of the most common pulmonary fibrotic conditions, idiopathic pulmonary fibrosis (IPF), is still unclear. This review examines common mechanisms of pulmonary wound-healing responses following lung injury, and highlights the pathogenesis of some of the most widespread pulmonary fibrotic diseases. A three phase model of wound repair is reviewed that includes; (1) injury; (2) inflammation; and (3) repair. In most pulmonary fibrotic conditions dysregulation at one or more of these phases has been reported. Chronic inflammation can lead to an imbalance in the production of chemokines, cytokines, growth factors, and disrupt cellular recruitment. These changes coupled with excessive pro-fibrotic IL-13 and/or TGFbeta1 production can turn a well-controlled healing response into a pathogenic fibrotic response. Endogenous regulatory mechanisms are discussed including novel areas of therapeutic intervention. Restoring homeostasis to these dysregulated healing responses, or simply neutralizing the key pro-fibrotic mediators may prevent or slow the progression of pulmonary fibrosis.

Chronic hypersensitivity pneumonitis: CT features comparison with pathologic evidence of fibrosis and survival

PURPOSE

To retrospectively compare in patients with chronic hypersensitivity pneumonitis (HP) the computed tomographic (CT) imaging features suggestive of fibrosis with pathologic evidence of fibrosis at surgical lung biopsy and to compare a usual interstitial pneumonia (UIP) pattern at CT with survival.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for this study, which was HIPAA compliant. Twenty-six patients (15 women, 11 men; age range, 37-76 years) with chronic HP had their surgical lung biopsy results reviewed by two pathologists for the presence of fibrosis. Two radiologists systematically reviewed the CT scans. The two radiologists were blinded to all clinical information, including pathologic diagnosis, patient information, and outcomes. The combination of a subpleural reticular pattern and lower zone predominance was considered a UIP pattern. CT findings were compared with the histopathologic presence of fibrosis, physiologic parameters, symptoms, and survival. The chi(2) or Fisher exact test (each two-tailed) was used to compare nominal and ordinal variables. A t test (with unequal variances) was used to compare continuous variables. The log-rank procedure was used to compare Kaplan-Meier survival curves.

RESULTS

Fifteen patients had fibrotic HP at biopsy, and 11 had nonfibrotic HP. Patients with fibrotic HP had more extensive reticular pattern and were more likely to have traction bronchiectasis, honeycombing, and a UIP pattern than those with nonfibrotic HP (P = .015, P = .007, P = .007, respectively). Although the presence of histologic fibrosis was associated with decreased survival (P = .003), the CT features were not associated with decreased survival.

CONCLUSION

CT findings of extensive reticular pattern, traction bronchiectasis, and honeycombing are closely related to the presence of histologic fibrosis in chronic HP.

Extrinsic allergic alveolitis: comparative study of the bronchoalveolar lavage profiles and radiological presentation

INTRODUCTION

Extrinsic allergic alveolitis (EAA) is an immunologically mediated interstitial lung disease. The abnormalities in the bronchoalveolar lavage (BAL) fluid cell counts are almost always seen in patients with EAA according to the stage of the disease. The aim of this retrospective study was to find out how the BAL lymphocyte count, percentage of lymphocytes expressing HLA-DR, CD4/CD8 T cell ratio in BAL fluid, and the concentration of immunoglobulin G in serum correspond to the inflammatory activity of the disease.

METHODS

The study included 14 patients with EAA. BAL fluid samples were obtained and processed for cytological and cytometric analysis. Immunoglobulin G serum concentrations were measured. High resolution computed tomography (HRCT) scoring system modified by Gay was used for establishing the alveolar and interstitial score in each patient.

CONCLUSIONS

It was found that subjects with normal value of CD4/CD8 ratio in BAL fluid had higher interstitial HRCT score. Clinical presentation, continuous exposure to the causative antigens, and BAL lymphocyte count positively correlated with the alveolar HRCT score. It is proposed that the increased BAL lymphocyte count could be the predictor of the inflammatory activity of the disease, especially in people with lasting exposure to the offending antigen.

Les pneumopathies d’hypersensibilité en milieu professionnel

INTRODUCTION

Hypersensitivity pneumonitis (HP) is a granulomatous disease of the lungs due to immune reactions following chronic inhalation of organic dusts or chemicals especially encountered in the occupational environment. The main purpose of this review is to report current concepts regarding aetiologies, epidemiology, diagnosis, treatment as well as legal aspects of HP.

STATE OF THE ART

The following aspects will be focused: (1) increase in new etiological circumstances, especially occupational and news antigens, (2) for diagnosis, the major contribution of chest high resolution CT scan which often shows characteristic images but also recent developments in simple diagnostic criteria that may be used for an epidemiological approach, (3) importance of bronchial obstruction and even emphysema as a long term sequelae, finally (4) the possibility of continuing occupational activities in certain circumstances where preventive measures can be used.

PERSPECTIVES

The increasing knowledge of etiological agents and circumstances as well as the development of secondary and especially primary preventive measures should lead to reduce the frequency of this disease and of its medico-social consequences.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a pulmonary disease with symptoms of dyspnea and cough resulting from the inhalation of an antigen to which the subject has been previously sensitized. The incidence of HP is unknown. A population-based study estimated the annual incidence of interstitial lung diseases as 30:100,000 and HP accounted for less than 2% of these cases. The diagnosis of HP can often be made or rejected with confidence, especially in areas of high or low prevalence respectively, using simple diagnostic criteria. Chest X-rays may be normal in active HP; High Resolution Computed Tomography is sensitive but not specific for the diagnosis of HP. The primary use of pulmonary function tests is to determine the physiologic abnormalities and the associated impairment. Despite the pitfalls of false positive and false negatives, antigen-specific IgG antibodies analysis can be useful as supportive evidence for HP. Bronchoalveolar lavage plays an important role in the investigation of patients suspected of having HP. A normal number of lymphocytes rules out all but residual disease. Surgical lung biopsy should be reserved for rare cases with puzzling clinical presentation or for verification the clinical diagnosis when the clinical course or response to therapy is unusual. Being an immune reaction in the lung, the most obvious treatment of HP is avoidance of contact with the offending antigen. Systemic corticosteroids represent the only reliable pharmacologic treatment of HP but do not alter the long-term outcome. The use of inhaled steroids is anecdotal. Treatment of chronic or residual disease is supportive.

Fatal hypersensitivity pneumonitis

BACKGROUND

Hypersensitivity pneumonitis (HP) is an uncommon, non-IgE-mediated interstitial lung disease caused by the inhalation of a variety of organic dusts, most commonly from exposure at work or in the pursuit of hobbies. Typically, after the disease is recognized, the causative allergen or environment is identified and treatment initiated through avoidance measures and corticosteroids. Progression of the disease is then usually halted and even reversed. Fatal cases of HP are unusual.

OBJECTIVE

To report a case of progressive and deadly HP in a 40-year-old printer who developed subacute bird fancier's disease with its clinical characteristics and positive precipitins to pigeon proteins.

METHODS

Chest x-ray examinations and tests of lung function were performed in the patient. Two months after initial consultation, when the diagnosis was still elusive, an open lung biopsy was performed and the patient was treated with prednisone for 3 months. A subsequent chest x-ray examination was performed 4 months after the biopsy.

RESULTS

With avoidance of birds and treatment with corticosteroids, the patient's symptoms resolved and lung function normalized. He was subsequently diagnosed as having asthma followed by bronchitis and 2 episodes of pneumonia. He did not fully recover from these but developed progressive dyspnea. After linking his symptoms to work by history, he underwent lung biopsy with findings consistent with chronic HP. Serum antibody titers were positive for Aspergillus but not pigeon proteins. Based on exposure to water-based coolants, he was suspected of having chronic occupational HP, although this could not be confirmed. Despite aggressive treatment, he developed a progressive course that was ultimately fatal.

CONCLUSIONS

This report details the progressive disease course in an individual who presented initially with subacute HP. Unfortunately, even after appropriate diagnosis and management, the course of the disease can be fatal.

Needs and Opportunities for Research in Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) develops after inhalation of many different environmental antigens, causing variable clinical symptoms that often make diagnosis uncertain. The prevalence of HP is higher than recognized, especially its chronic form. Mechanisms of disease are still incompletely known. Strategies to improve detection and diagnosis are needed, and treatment options, principally avoidance, are limited. A workshop recommended: a population-based study to more accurately document the incidence and prevalence of HP; better classification of disease stages, including natural history; evaluation of diagnostic tests and biomarkers used to detect disease; better correlation of computerized tomography lung imaging and pathologic changes; more study of inflammatory and immune mechanisms; and improvement of animal models that are more relevant for human disease.