Anti-avian antibodies and rheumatoid factor in pigeon hypersensitivity pneumonitis

[Diagnosis and Treatment of Hypersensitivity Pneumonitis - S2k Guideline of the German Respiratory Society and the German Society for Allergology and Clinical Immunology]

Hypersensitivity pneumonitis (HP) is an immune-mediated interstitial lung disease (ILD) in sensitized individuals caused by a large variety of inhaled antigens. The clinical form of acute HP is often misdiagnosed, while the chronic form, especially the chronic fibrotic HP, is difficult to differentiate from other fibrotic ILDs. The present guideline for the diagnosis and treatment of HP replaces the former German recommendations for the diagnosis of HP from 2007 and is amended explicitly by the issue of the chronic fibrotic form, as well as by treatment recommendations for the first time. The evidence was discussed by a multidisciplinary committee of experts. Then, recommendations were formulated for twelve questions on important issues of diagnosis and treatment strategies. Recently published national and international guidelines for ILDs and HP were considered. Detailed background information on HP is useful for a deeper insight into HP and the handling of the guideline.

Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report

BACKGROUND

The purpose of this analysis is to provide evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.

STUDY DESIGN AND METHODS

Approved panelists developed key questions regarding the diagnosis of HP using the PICO (Population, Intervention, Comparator, Outcome) format. MEDLINE (via PubMed) and the Cochrane Library were systematically searched for relevant literature, which was supplemented by manual searches. References were screened for inclusion, and vetted evaluation tools were used to assess the quality of included studies, to extract data, and to grade the level of evidence supporting each recommendation or statement. The quality of the evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Graded recommendations and ungraded consensus-based statements were drafted and voted on using a modified Delphi technique to achieve consensus. A diagnostic algorithm is provided, using supporting data from the recommendations where possible, along with expert consensus to help physicians gauge the probability of HP.

RESULTS

The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations and 2 ungraded consensus-based statements. All evidence was of very low quality.

INTERPRETATION

Diagnosis of HP should employ a patient-centered approach and include a multidisciplinary assessment that incorporates the environmental and occupational exposure history and CT pattern to establish diagnostic confidence prior to considering BAL and/or lung biopsy. Criteria are presented to facilitate diagnosis of HP. Additional research is needed on the performance characteristics and generalizability of exposure assessment tools and traditional and new diagnostic tests in modifying clinical decision-making for HP, particularly among those with a provisional diagnosis.

Executive Summary: Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report

BACKGROUND

The purpose of this summary is to provide a synopsis of evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.

STUDY DESIGN AND METHODS

Approved panelists developed key questions regarding the diagnosis of HP using the PICO (Population, Intervention, Comparator, and Outcome) format. MEDLINE (via PubMed) and the Cochrane Library were systematically searched for relevant literature, which was supplemented by manual searches. References were screened for inclusion and vetted evaluation tools were used to assess the quality of included studies, to extract data, and to grade the level of evidence supporting each recommendation or statement. The quality of the evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Graded recommendations and ungraded consensus-based statements were drafted and voted on using a modified Delphi technique to achieve consensus.

RESULTS

The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations, and 2 ungraded consensus-based statements. All evidence was of very low quality.

INTERPRETATION

Diagnosis of HP should employ a patient-centered approach and include a multidisciplinary assessment that incorporates the environmental and occupational exposure history and CT pattern to establish diagnostic confidence prior to considering BAL and/or lung biopsy. Additional research is needed on the performance characteristics and generalizability of exposure assessment tools and traditional and new diagnostic tests in modifying clinical decision-making for HP, particularly among those with a provisional diagnosis.

Immunosuppressive effects of mesenchymal stem cells on lung B cell gene expression in LPS-induced acute lung injury

Background

Immune system disorders play important roles in acute lung injury (ALI), and mesenchymal stem cell (MSC) treatment can reduce inflammation during ALI. In this study, we compared the changes in lung B cells during MSC treatment.

Methods

We investigated the effects of MSCs on lung B cells in a mouse model of lipopolysaccharide (LPS)-induced ALI. MSCs were administered intratracheally 4 h after LPS. As vehicle-treated controls, mice were treated with phosphate-buffered saline (PBS) containing 2% C57BL/6 (PBS group). Histopathological changes, survival rate, inflammatory factor levels, and the number of neutrophils in bronchoalveolar lavage fluid (BALF) were determined. Single-cell RNA sequencing (scRNA-Seq) analysis was performed to evaluate the transcriptional changes in lung B cells between the PBS, LPS, and LPS/MSC groups on days 3 and 7.

Results

MSC treatment ameliorated LPS-induced ALI, as indicated by the reductions in mortality, the levels of chemokines and cytokines in BALF, and the severity of lung tissue histopathology in ALI mice. Lung B cells in the PBS group remained undifferentiated and had an inhibitory phenotype. Based on our scRNA-Seq results, the differentially expressed genes (DEGs) in lung B cells in both the PBS group and LPS group were involved in chemotaxis processes and some proinflammatory pathways. MSC treatment inhibited the expression of chemokine genes that were upregulated by LPS and were related to the recruitment of neutrophils into lung tissues. Immunoglobulin-related gene expression was decreased in lung B cells of mice treated with LPS/MSC for 7 days. The DEGs regulated by MSCs were enriched in biological processes, including humoral immune response and apoptotic signaling.

Conclusions

Lung B cells played an important role in the effects of treatment of ALI with MSCs. These observations provide new insights into the mechanisms underlying the effects of MSC treatment for ALI.

Screening and Preliminary Verification of a Phage Display Single-Chain Antibody Library Against Coal Workers' Pneumoconiosis

OBJECTIVES

To construct a phage display human antibody library (PDHAL) against pneumoconiosis for the diagnosis and treatment of coal worker pneumoconiosis (CWP).

METHODS

The PDHAL was established via CWP blood and six positive antibodies were discovered. 867 coal workers (558 CWP and 309 without CWP) and 393 controls were recruited to validate the results.

RESULTS

A PDHAL against CWP was established, from which six strong positive clones were selected, sequenced and identified as VEGF, interleukin-18, HSP70, HER3, Gz-B and RF. Logistic regression analysis revealed that VEGF (OR (95% CI), 0.02 (0.01to 0.07), P < 0.05), RF-Ab (OR (95% CI): 0.46 (0.28 to 0.73), P < 0.05) and HSP70/HSP-70-Ab (OR (95% CI): 0.71 (0.53 to 0.95), P < 0.05) were protective factors for CWP after adjustment of confounding factors.

CONCLUSION

The serum VEGF, RF-Ab and HSP-70/HSP-70 antibodies were potential biomarkers for diagnosis and treatment of CWP.

Immunization of BALB/c mice with pigeon IgY induces the production of anti-IgG autoantibodies

The breakdown of immunological tolerance due to the activation of autoreactive B and T cells triggers physiopathological processes. An example of such conditions is the production of IgG autoantibodies specific for the Fc portion of IgG (anti-Fcγ IgG). Previous reports have shown that patients with pigeon-related hypersensitivity pneumonitis exhibit an increase in the serum levels of anti-Fcγ IgG. There is no in vivo model for the study of this condition and the immunological mechanisms of tolerance breakdown associated with sensitization by pigeon antigens are still unknown. In this work, we show that the repeated immunization of BALB/c mice with pigeon IgY during 16-weeks induces the production of anti-Fcγ IgG and keeps their high levels for seven weeks. The late appearance of anti-Fcγ IgG autoantibodies in the plasma is similar to what has been reported in other experimental autoimmune models. With the occurrence of anti-Fcγ IgG, there is a reduction in the proportion of Foxp3 + cells (regulatory T cells, Tregs) within the population of splenic CD4 + CD25 + T cells. Thus, our data showed that the immunization of BALB/c mice with IgY promotes the production of anti-Fcγ IgG along with a decrease in Tregs in the spleen. We propose that immunization of mice with pigeon antigens, like IgY can provide a model to study the immunological mechanisms involved in the development of pigeon-related hypersensitivity pneumonitis.

Decline of Pulmonary Function Is Associated With the Presence of Rheumatoid Factor in Korean Health Screening Subjects Without Clinically Apparent Lung Disease: A Cross-Sectional Study

Although higher-than-normal levels of rheumatoid factor (RF) are often observed in subjects without specific medical problems, little is known about the influence of RF on pulmonary function in health screening subjects. This study aimed to determine the association between the presence of RF and decreased pulmonary function in Korean health screening subjects without any history of joint disease or clinically apparent lung disease.A total of 115,641 study subjects (age range, 18-88 years) participated in the health checkup program. We excluded subjects who did not have pulmonary function test, as well as those with abnormal chest radiographs. Subjects with medical history of arthritis including rheumatoid arthritis, and lung disease based on the self-reported questionnaire. Final analysis was performed on 94,438 Koreans (41,261 women).RF-positive subjects had a lower forced vital capacity (FVC) predicted value and forced expiratory volume in 1 s (FEV1) predicted value than RF-negative subjects (82.8 ± 11.5% vs 83.8 ± 11.4% for FVC% predicted and 83.5 ± 13.0% vs 85.1 ± 12.9% for FEV1% predicted, P < 0.001 for both). RF positivity was significantly associated with the decline of FEV1% predicted regardless of smoking history (adjusted odds ratio [OR] = 1.289 [95% confidence interval [CI] 1.163-1.429], P < 0.001 for nonsmokers and adjusted OR = 1.138 [95% CI 1.004-1.289], P < 0.001 for smokers) while the decline of FVC% predicted only in nonsmokers (adjusted OR = 1.251 [95% CI 1.133-1.382], P < 0.001). Our results suggest that the presence of RF could impact pulmonary function in apparently healthy subjects. A follow-up study to investigate serial changes in pulmonary function may reveal the actual influence of raised RF titers.

B-lymphocyte lineage cells and the respiratory system

Adaptive humoral immune responses in the airways are mediated by B cells and plasma cells that express highly evolved and specific receptors and produce immunoglobulins of most isotypes. In some cases, such as autoimmune diseases or inflammatory diseases caused by excessive exposure to foreign antigens, these same immune cells can cause disease by virtue of overly vigorous responses. This review discusses the generation, differentiation, signaling, activation, and recruitment pathways of B cells and plasma cells, with special emphasis on unique characteristics of subsets of these cells functioning within the respiratory system. The primary sensitization events that generate B cells responsible for effector responses throughout the airways usually occur in the upper airways, tonsils, and adenoid structures that make up the Waldeyer ring. On secondary exposure to antigen in the airways, antigen-processing dendritic cells migrate into secondary lymphoid organs, such as lymph nodes, that drain the upper and lower airways, and further B-cell expansion takes place at those sites. Antigen exposure in the upper or lower airways can also drive expansion of B-lineage cells in the airway mucosal tissue and lead to the formation of inducible lymphoid follicles or aggregates that can mediate local immunity or disease.

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.

Chronic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of environmental antigens. Chronic HP may mimic other fibrotic lung diseases, such as idiopathic pulmonary fibrosis. Recognition of the antigen is important for diagnosis; avoidance of further exposure is critical for treatment. Fibrosis on biopsy or high-resolution computed tomography is a predictor of increased mortality. Additional research is needed to understand why the disease develops only in a minority of exposed individuals and why cases of chronic HP may progress without further antigen exposure.

IgM, IgG, and IgA rheumatoid factors in pigeon hypersensitivity pneumonitis

The association of rheumatoid factor (RF) and lung disease in several immunologically mediated conditions has suggested that it may be physiopathologically relevant. Since previous reports in hypersensitivity pneumonitis (HP) have dealt mainly with the immunoglobulin M (IgM) RF measurement, we studied such antibody activity in other immunoglobulins, to determine the IgG and IgA RF levels in pigeon-HP, and in asymptomatic breeders (AB) and rheumatoid arthritis (RA) as controls. RFs were measured in 35 HP patients, 41 AB, 31 RA controls, and 55 healthy donors by enzyme-linked immunosorbent assay (ELISA) using human or rabbit immunoglobulin G (IgG), anti-IgM, F(ab')2 of IgG, and IgA F(ab')2 conjugates. An affinity chromatography, fragment crystallizable (Fc) preparations of IgG, pepsin digestion, and Western blots were used to confirm RF specificity. We also evaluated anti-avian antibodies (AA) and cross-reacting antibodies. The HP group revealed positive IgM (51.4%), IgG (31.4%), and immunoglobulin A (IgA) (34.2%) RF tests, and these antibody values exceeded the AB reference levels (P<0.02). HP and RA showed a similar frequency and distribution of RFs. Possible immunoassay interferences were excluded. As in other immunologically mediated diseases, IgG and IgA RFs may play a pathogenic role in HP, amplifying the inflammatory reaction, immune-complex formation, and complement activation. IgM-RF producing cells that have been implicated in the presentation of self and foreign antigens, and T-cell activation might induce the isotype switching of RFs.

Extrinsic allergic alveolitis

Extrinsic allergic alveolitis (also known as hypersensitivity pneumonitis) is caused by repeated inhalation of mainly organic antigens by sensitized subjects. This induces a hypersensitivity response in the distal bronchioles and alveoli and subjects may present clinically with a variety of symptoms. The aims of this review are to describe the current concepts of the immunological response, the diverse clinical presentation of this disease, the relevant investigations and management, and areas for future studies.

Interstitial lung disease in the patient who has connective tissue disease

Interstitial lung disease is a common complication of many of the connective tissue diseases. Because the prognosis, degree of reversibility, and optimal therapy differs for each disease presentation, a thorough knowledge of the pulmonary presentations of each connective tissue disease is important. Additionally, the challenge of finding the patient who has occult connective tissue disease in an interstitial lung disease clinic is discussed.