Proteomic Analysis of Kveim Reagent Identifies Targets of Cellular Immunity in Sarcoidosis

Human peripheral blood mononuclear cells as a valuable source of disease-related biomarkers: Evidence from comparative proteomics studies

PURPOSE

The discovery of specific and sensitive disease-associated biomarkers for early diagnostic purposes of many diseases is still highly challenging due to various complex molecular mechanisms triggered, high variability of disease-related interactions, and an overlap of manifestations among diseases. Human peripheral blood mononuclear cells (PBMCs) contain protein signatures corresponding to essential immunological interplay. Certain diseases stimulate PBMCs and contribute towards modulation of their proteome which can be effectively identified and evaluated via the comparative proteomics approach.

EXPERIMENTAL DESIGN

In this review, we made a detailed survey of the PBMCS-derived protein biomarker candidates for a variety of diseases, published in the last 15 years. Articles were preselected to include only comparative proteomics studies.

RESULTS

PBMC-derived biomarkers were investigated for cancer, glomerular, neurodegenerative/neurodevelopmental, psychiatric, chronic inflammatory, autoimmune, endocrinal, infectious, and other diseases. A detailed review of these studies encompassed the proteomics platforms, proposed candidate biomarkers, their immune cell type specificity, and potential clinical application.

CONCLUSIONS

Overall, PBMCs have shown a solid potential in giving early diagnostic and prognostic biomarkers for many diseases. The future of PBMC biomarker research should reveal its full potential through well-designed comparative studies and extensive testing of the most promising protein biomarkers identified so far.

Sarcoidosis and Autoimmune Inflammatory Syndrome Induced by Adjuvants

Currently, sarcoidosis remains one of the diseases with unknown etiology, which significantly complicates its diagnosis and treatment. Various causes of sarcoidosis have been studied for many years. Both organic and inorganic trigger factors, provoking the development of granulomatous inflammation are considered. However, the most promising and evidence-based hypothesis is the development of sarcoidosis as an autoimmune disease, provoked by various adjuvants in genetic predisposed individuals. This concept fits into the structure of the autoimmune/inflammatory syndrome, induced by adjuvants (ASIA) that was proposed in 2011 by Professor Shoenfeld Y. In this paper, the authors reveal the presence of major and minor ASIA criteria for sarcoidosis, propose a new concept of the course of sarcoidosis within the framework of ASIA, and point out the difficulties in creating a model of the disease and the selection of therapy. It is obvious that the data obtained not only bring us closer to understanding the nature of sarcoidosis, but also potentiate new studies confirming this hypothesis by obtaining a model of the disease.

The Overlap of Kidney Failure in Extrapulmonary Sarcoidosis in Children-Case Report and Review of Literature

Sarcoidosis is a non-necrotizing granulomatous inflammatory multisystemic disorder of unknown etiology. In children, as in adults, it can involve a few or all organ systems to a varying extent and degree, entailing multisystemic manifestations. Kidney involvement in pediatric-onset adult-type sarcoidosis is rare, with a wide range of renal manifestations, most of them related to calcium metabolism. Children with renal sarcoidosis tend to be more symptomatic than adults, although male patients have a higher prevalence. We present the case of a 10-year-old boy who presented with advanced renal failure with nephrocalcinosis and important hepatosplenomegaly. The diagnosis was established by histopathological examination, with consequent cortisone therapy and hemodialysis. This review emphasizes that sarcoidosis should be considered in the differential diagnosis of pediatric patients with acute kidney insufficiency or chronic kidney disease of an unknown etiology. As far as we know, this is the first study regarding extrapulmonary sarcoidosis in children from Romania.

Sarcoidosis and autoimmunity: In the depth of a complex relationship

Sarcoidosis is a chronic granulomatous disease that can virtually affect any organ. Its etiology is unknown, although it has been proposed that environmental or biological agents can act as triggers, ultimately leading to chronic inflammation in genetically predisposed individuals. The main component of sarcoid inflammation is represented by an exaggerated T- lymphocytic cellular response to a putative antigen that could not be efficiently cleared in the patient. However, several clinical and immunological observations, such as the association of sarcoidosis to autoimmune diseases or the presence of autoantibodies in the serum of patients with sarcoidosis, suggest that humoral-mediated immune response might also play a role in the pathogenesis of sarcoidosis. The aim of this review is to deepen the relationship between sarcoidosis and autoimmunity, by analyzing the most recent advances and proposing new fields of research.

Detection of Anti-Vimentin Antibodies in Patients with Sarcoidosis

There is a need to further characterize the antibody response to vimentin in relation to its possible involvement in pathogenicity of sarcoidosis and other lung disorders. Objectives: We investigated serum samples from patients with sarcoidosis, healthy controls and controls with other non-infectious lung diseases., to evaluate levels and frequency of these antibodies. Materials and methods: A retrospective-prospective comparative study was performed in the years 2015–2019. Sera from 93 patients with sarcoidosis, 55 patients with non-infectious lung diseases and 40 healthy subjects was examined for presence of autoantibodies to mutated citrullinated vimentin (anti-MCV). Patients with elevated anti-MCV levels were tested for antibodies to a cyclic citrullinated peptide (anti-CCP) and citrullinated vimentin (anti-Sa). In all cases ELISA assays was used. The results were considered statistically significant at p-value less than 0.05. Results of the study: The high concentrations of anti-MCV antibodies were more frequent in patients with sarcoidosis (40.9% of the cases, 38/93), compared to the control groups (23.6% and 25.0% of cases, respectively). In sarcoidosis, clinical symptoms similar to the autoimmune pathology were described. A moderate positive correlation between the anti-MCV and anti-Sa antibodies (r = 0.66) was found in 13 patients with sarcoidosis. There was no significant difference between the levels of the anti-MCV and the anti-CCP in patients with non-infectious lung diseases and the healthy control group. Conclusion: Antibodies to citrullinated cyclic peptides are not significant in the pathogenesis of sarcoidosis and other investigated pulmonary diseases (COPD, granulomatosis with polyangiitis, alveolitis) and based on their low concentration, it can be assumed that citrullination and modification of vimentin is not a key factor in the development of an autoimmune response in patients with sarcoidosis.

Systemic immune response to vimentin and granuloma formation in a model of pulmonary sarcoidosis

A characteristic feature of sarcoidosis is a dysregulated immune response to persistent stimuli, often leading to the formation of non-necrotizing granulomas in various organs. Although genetic susceptibility is an essential factor in disease development, the etiology of sarcoidosis is not fully understood. Specifically, whether autoimmunity contributes to the initiation or progression of the disease is uncertain. In this study, we investigated systemic autoimmunity to vimentin in sarcoidosis. IgG antibodies to human vimentin were measured in sera from sarcoidosis patients and healthy controls. Mice immunized with recombinant murine vimentin were challenged intravenously with vimentin-coated beads to mimic pulmonary sarcoidosis. Lungs from treated mice were studied for cellular infiltration, granuloma formation, and gene expression. Immune cells in the bronchoalveolar lavage fluid were evaluated by flow cytometry. Compared to healthy controls, sarcoidosis patients had a higher frequency and levels of circulating anti-vimentin IgG. Vimentin-immunized mice developed lung granulomas following intravenous challenge with vimentin-coated beads. These sarcoidosis-like granulomas showed the presence of Langhans and foreign body multinucleated giant cells, CD4 T cells, and a heterogeneous collection of MHC II positive and arginase 1-expressing macrophages. The lungs showed upregulated pro-inflammatory gene expression, including Ifng, Il17, and Tnfa, reflecting TH1/TH17 responses typical of sarcoidosis. In addition, genes in the TH2 canonical pathway were also upregulated, congruent with increased numbers of ILC2 in the bronchoalveolar lavage. Overall, these results further validate vimentin as an autoantigen in sarcoidosis and provide evidence for an anti-vimentin immune response in disease pathogenesis. Our study also highlights the possible role of ILC2-driven TH2-like responses in the formation of lung granulomas in sarcoidosis.

Human peripheral blood mononuclear cells: A review of recent proteomic applications

Human peripheral blood mononuclear cells (PBMCs) represent a sentinel blood sample which reacts to different pathophysiological stimuli in the form of immunological responses/immunophenotypic changes. The study of molecular content of PBMCs can provide better understanding of immune processes giving the possibility of monitoring the health conditions of the host organism. Proteomic analysis of PBMCs can achieve mentioned goal as important immune-related biomarkers are easily accessible for analysis. PBMCs have been gaining attention in different research areas including preclinical or clinical investigations. In this review, recent applications of proteomic analysis of PBMCs are described and discussed. Approaches are divided based on different proteomic workflows such as in-gel, in-solution and on-filter modes. The effect of various diseases such as autoimmune, cancer, neurodegenerative, viral, metabolic, and various immune stimulations such as radiation, vaccine, corticosteroids over PBMCs proteome, are described with emphasis on promising protein biomarker candidates. This article is protected by copyright. All rights reserved.

Sarcoidosis and autoimmunity

PURPOSE OF REVIEW

Sarcoidosis is a poorly understood multisystem granulomatous disease that frequently involves the lungs but can affect any organ system. In this review, we summarize recent developments in the understanding of the immune dysregulation seen in sarcoidosis and propose a new expanded definition of human autoimmunity in sarcoidosis, and the implications it would have on treating sarcoidosis with targeted immunotherapy regimens in the future.

RECENT FINDINGS

Sarcoidosis has been linked to infectious organisms like Mycobacterium and Cutibacterium, and certain manifestations of sarcoidosis have been linked to specific HLA alleles, but the overall pathogenesis remains uncertain. Sarcoidosis patients have similar patterns of cellular immune dysregulation seen in other autoimmune diseases like rheumatoid arthritis, and recent large-scale population studies show that sarcoidosis frequently presents with other autoimmune diseases.

SUMMARY

Advancements in the understanding of sarcoidosis support its consideration as an autoimmune disease. Sarcoidosis patients carry a higher risk of comorbid autoimmune conditions which offers an excellent opportunity to further understand autoimmunity and explore biologic therapies in sarcoidosis treatment, and furthermore will better targeted immunotherapy regimens for sarcoidosis patients in the future.

Inflammatory Pathways in Sarcoidosis

Concepts regarding etiology and pathophysiology of sarcoidosis have changed remarkably within the past 5 years. Sarcoidosis is now viewed as a complex multi-causation disease related to a diverse collection of external environmental or infectious signals. It is generally accepted that the cause of sarcoidosis is unknown. Moreover, concepts of the inflammatory pathway have been modified by the realization that intrinsic genetic factors and innate immunity may modify adaptive immune responses to external triggers. With those potential regulatory pathways in mind, we will attempt to discuss the current understanding of the inflammatory response in sarcoidosis with emphasis on development of pulmonary granulomatous pathology. In that context, we will emphasize that both macrophages and T lymphocytes play key roles, with sometimes overlapping cytokine production (i.e., TNFα and IFN-γ) but also with unique mediators that influence the pathologic picture. Numerous studies have shown that in a sizable number of sarcoidosis patients, granulomas spontaneously resolve, usually within 3 years. Other sarcoidosis patients, however, may develop a chronic granulomatous disease which may subsequently lead to fibrosis. This chapter will outline our current understanding of inflammatory pathways in sarcoidosis which initiate and mediate granulomatous changes or onset of pulmonary fibrosis.

Presence of concurrent sarcoid-like granulomas indicates better survival in cancer patients: a retrospective cohort study

Introduction

An increased risk of sarcoidosis and sarcoid-like reactions in subjects with a history of malignancy has been suggested. We assessed the incidence and clinical characteristics of cancer patients with biopsies containing sarcoid-like granulomas on cancer metastasis and patient survival.

Methods

This is a retrospective, multicentre, observational study involving endobronchial ultrasound transbronchial needle aspiration and a melanoma patient dataset at the University of Miami, USA, and a sarcoidosis patient database at Chiba University, Japan. Subjects with a confirmed diagnosis of cancer and who subsequently developed granulomas in different organs were enrolled. The study was registered at Clinicaltrials.gov (NCT03844698).

Results

133 patients met the study's criteria. The most common primary cancer sites were the skin (22.5%), breast (20.3%) and lymph node (12.8%). 24 (18%) patients developed sarcoid-like granulomas within 1 year of cancer diagnosis, 54 (40.6%) between 1 and 5 years and 49 (36.8%) after 5 years. Imaging showed possible sarcoid-like granulomas in lymph nodes in 51 cases (38.3%) and lung tissue and mediastinal lymph nodes in 73 cases (54.9%); some parenchymal reticular opacity and fibrosis was found in 5 (3.7%) and significant parenchymal fibrosis in 2 (1.5%) subjects. According to logistic regression analysis, the frequency of metastatic cancer was significantly lower in patients with sarcoid-like granulomas than in controls. Moreover, multivariate Cox proportional hazard analysis showed a significant survival advantage in those with sarcoid-like granuloma.

Conclusion

Sarcoid-like granulomas are uncommon pathology findings in cancer patients. There is a significant association between the presence of granulomas and reduced metastasis and increased survival. Further study is warranted to understand the protective mechanism involved.

Classical Examples of the Concept of the ASIA Syndrome

Autoimmune/inflammatory syndrome induced by adjuvants (ASIA) was first introduced in 2011 by Shoenfeld et al. and encompasses a cluster of related immune mediated diseases, which develop among genetically prone individuals as a result of adjuvant agent exposure. Since the recognition of ASIA syndrome, more than 4400 documented cases have been reported so far, illustrated by heterogeneous clinical manifestations and severity. In this review, five enigmatic conditions, including sarcoidosis, Sjögren's syndrome, undifferentiated connective tissue disease, silicone implant incompatibility syndrome (SIIS), and immune-related adverse events (irAEs), are defined as classical examples of ASIA. Certainly, these disorders have been described after an adjuvant stimulus (silicone implantation, drugs, infections, metals, vaccines, etc.) among genetically predisposed individuals (mainly the HLA-DRB1 and PTPN22 gene), which induce an hyperstimulation of the immune system resulting in the production of autoantibodies, eventually leading to the development of autoimmune diseases. Circulating autonomic autoantibodies in the sera of patients with silicone breast implants, as well as anatomopathological aspects of small fiber neuropathy in their skin biopsies have been recently described. To our knowledge, these novel insights serve as a common explanation to the non-specific clinical manifestations reported in patients with ASIA, leading to the redefinition of the ASIA syndrome diagnostic criteria.

Key Players and Biomarkers of the Adaptive Immune System in the Pathogenesis of Sarcoidosis

Sarcoidosis is a systemic inflammatory disease characterized by development of granulomas in the affected organs. Sarcoidosis is often a diagnosis of exclusion, and traditionally used tests for sarcoidosis demonstrate low sensitivity and specificity. We propose that accuracy of diagnosis can be improved if biomarkers of altered lymphocyte populations and levels of signaling molecules involved in disease pathogenesis are measured for patterns suggestive of sarcoidosis. These distinctive biomarkers can also be used to determine disease progression, predict prognosis, and make treatment decisions. Many subsets of T lymphocytes, including CD8⁺ T-cells and regulatory T-cells, have been shown to be dysfunctional in sarcoidosis, and the predominant CD4⁺ T helper cell subset in granulomas appears to be a strong indicator of disease phenotype and outcome. Studies of altered B cell populations, B cell signaling molecules, and immune complexes in sarcoidosis patients reveal promising biomarkers as well as possible explanations of disease etiology. Furthermore, examined biomarkers raise questions about new treatment methods and sarcoidosis antigens.

Simultaneous testing of immunological sensitization to multiple antigens in sarcoidosis reveals an association with inorganic antigens specifically related to a fibrotic phenotype

Organic and inorganic antigens were studied simultaneously in the same cohort of sarcoidosis patients to investigate whether correlations between clinical characteristics and immunological sensitization could reveal new phenotypes. Sensitization to antigens of mycobacteria, Propionibacterium acnes catalase and vimentin was investigated in 201 sarcoidosis and 51 obstructive sleep apnoea patients, serving as control group. Sensitization to aluminium, beryllium, silica and zirconium was also studied in 105 of the sarcoidosis patients and in 24 of the controls. A significantly higher percentage of sarcoidosis patients (27·6%) than controls (4·2%) had an immunological response to metals or silica (P = 0·014). A higher percentage of these sarcoidosis patients showed fibrosis on chest X-ray 5 years after the diagnosis (69·2 versus 30·3%, P = 0·016). No significant differences in mycobacterial or vimentin enzyme-linked immunospot (ELISPOT) assay results were observed between sarcoidosis and control patients. A significantly lower percentage of sarcoidosis patients (3·5%) than control patients (15·7%) had a positive ELISPOT for P. acnes catalase (P = 0·003). However, sarcoidosis patients sensitized to P. acnes catalase were more likely to have skin involvement, while sarcoidosis patients sensitized to mycobacterial antigens were more likely to have cardiac involvement. Our study suggests a more prominent role for inorganic triggers in sarcoidosis pathogenesis than previously thought. Immunological sensitization to inorganic antigens was associated with development of fibrotic sarcoidosis. No association was found between sensitization to bacterial antigens or vimentin and sarcoidosis in Dutch patients. However, our data suggest that trigger-related phenotypes can exist in the heterogeneous population of sarcoidosis patients.

Clinical Presentations, Pathogenesis, and Therapy of Sarcoidosis: State of the Art

Sarcoidosis is a systemic disease of unknown etiology characterized by the presence of noncaseating granulomas that can occur in any organ, most commonly the lungs. Early and accurate diagnosis of sarcoidosis remains challenging because initial presentations may vary, many patients are asymptomatic, and there is no single reliable diagnostic test. Prognosis is variable and depends on epidemiologic factors, mode of onset, initial clinical course, and specific organ involvement. From a pathobiological standpoint, sarcoidosis represents an immune paradox, where an excessive spread of both the innate and the adaptive immune arms of the immune system is accompanied by a state of partial immune anergy. For all these reasons, the optimal treatment for sarcoidosis remains unclear, with corticosteroid therapy being the current gold standard for those patients with significantly symptomatic or progressive pulmonary disease or serious extrapulmonary disease. This review is a state of the art of clinical presentations and immunological features of sarcoidosis, and the current therapeutic approaches used to treat the disease.

Environmental Risk Factors for Sarcoidosis

Sarcoidosis is a multisystem granulomatous disease that may affect any body organ. Sarcoidosis is associated with many environmental and occupational exposures. Because the exact immunopathogenesis of sarcoidosis is unknown, it is not known whether these exposures are truly causing sarcoidosis, rendering the immune system more susceptible to the development of sarcoidosis, exacerbating subclinical cases of sarcoidosis, or causing a granulomatous condition distinct from sarcoidosis. This manuscript outlines what is known about the immunopathogenesis of sarcoidosis and postulates mechanisms whereby these exposures could cause or exacerbate the disease. We also describe the varied environmental and occupational exposures that have been associated with sarcoidosis. This includes potential infectious exposures such as mycobacteria and Propionibacterium acnes, a skin commensal bacterium, as well as non-infectious environmental exposures including inhaled bioaerosols, metal dusts and products of combustion. Further insights concerning the relationship of environmental exposures to the development of sarcoidosis may have a major impact on the prevention and treatment of this enigmatic disease.

Imbalance in B cell and T Follicular Helper Cell Subsets in Pulmonary Sarcoidosis

Sarcoidosis is a systemic granulomatous disease that develops due to the Th1, Th17 and Treg lymphocytes disturbance. There is an assumption, that B cells and follicular T-helper (Tfh) cells may play an important role in this disorder, as well as in several other autoimmune diseases. The aim of this study was to determine CD19+ B cells subset distribution in the peripheral blood and to define disturbance in the circulating Tfh cells subsets in patients with sarcoidosis. The prospective comparative study was performed in 2016-2018, where peripheral blood B cell subsets and circulating Tfh cell subsets were analyzed in 37 patients with primarily diagnosed sarcoidosis and 35 healthy donors using multicolor flow cytometry. In the results of our study we found the altered distribution of peripheral B cell subsets with a predominance of "naïve" (IgD + CD27-) and activated B cell (Bm2 and Bm2') subsets and a decreased frequency of memory cell (IgD+ CD27+ and IgD- CD27+) in peripheral blood of sarcoidosis patients was demonstrated. Moreover, we found that in sarcoidosis patients there are increased levels of B cell subsets, which were previously shown to display regulatory capacities (CD24+++ CD38+++ and CD5 + CD27-). Next, a significantly higher proportion of CXCR5-expressing CD45RA - CCR7+ Th cells in patients with sarcoidosis in comparison to the healthy controls was revealed, that represents the expansion of this memory Th cell subset in the disease. This is the first study to demonstrate the association between the development of sarcoidosis and imbalance of circulating Tfh cells, especially CCR4- and CXCR3-expressing Tfh subsets. Finally, based on our data we can assume that B cells and Tfh2- and Tfh17-like cells - most effective cell type in supporting B-cell activity, particularly in antibody production - may be involved in the occurrence and development of sarcoidosis and in several other autoimmune conditions. Therefore, we can consider these results as a new evidence of the autoimmune mechanisms in the sarcoidosis development.

Sarcoidosis as an Autoimmune Disease

Despite the large number of performed studies, the etiology and pathogenesis of sarcoidosis still remain unknown. Most researchers allude to the possible autoimmune or immune-mediated genesis of the disease. This review attempts an integral analysis of currently available information suggesting an autoimmune genesis of sarcoidosis and is divided into four categories: the evaluation of clinical signs described both in patients with sarcoidosis and “classic” autoimmune diseases, the role of triggering factors in the development of sarcoidosis, the presence of immunogenic susceptibility in the development of the disease, and the analysis of cellular and humoral immune responses in sarcoidosis. Studying the etiology and pathogenesis of sarcoidosis will improve diagnostic procedures as well as the prognosis and patients' quality of life.

Immune response biomarkers as indicators of sarcoidosis presence, prognosis, and possible treatment: An Immunopathogenic perspective

Sarcoidosis has been a disease of puzzling occurrence and clinical course. Multiple immunological markers have been noted to be altered within sarcoidosis, however there is variable consistency among these reports. Previous studies have shown sarcoidosis to be a primary T cell-mediated disease, yet new data concerning B cell and mycobacterial involvement have been brought to light. The possibility of a uniform biomarker to characterize sarcoidosis presence, severity and prognosis greatly increases the movement towards directed and specialized treatment for this rare disease.

New advances in the management of pulmonary sarcoidosis

Sarcoidosis is a highly variable granulomatous multisystem syndrome. It affects individuals in the prime years of life; both the frequency and severity of sarcoidosis are greater in economically disadvantaged populations. The diagnosis, assessment, and management of pulmonary sarcoidosis have evolved as new technologies and therapies have been adopted. Transbronchial needle aspiration guided by endobronchial ultrasound has replaced mediastinoscopy in many centers. Advanced imaging modalities, such as fluorodeoxyglucose positron emission tomography scanning, and the widespread availability of magnetic resonance imaging have led to more sensitive assessment of organ involvement and disease activity. Although several new insights about the pathogenesis of sarcoidosis exist, no new therapies have been specifically developed for use in the disease. The current or proposed use of immunosuppressive medications for sarcoidosis has been extrapolated from other disease states; various novel pathways are currently under investigation as therapeutic targets. Coupled with the growing recognition of corticosteroid toxicities for managing sarcoidosis, the use of corticosteroid sparing anti-sarcoidosis medications is likely to increase. Besides treatment of granulomatous inflammation, recognition and management of the non-granulomatous complications of pulmonary sarcoidosis are needed for optimal outcomes in patients with advanced disease.

Moving target: shifting the focus to pulmonary sarcoidosis as an autoimmune spectrum disorder

Despite more than a century of research, the causative agent(s) in sarcoidosis, a heterogeneous granulomatous disorder mainly affecting the lungs, remain(s) elusive. Following identification of genetic factors underlying different clinical phenotypes, increased understanding of CD4⁺ T-cell immunology, which is believed to be central to sarcoid pathogenesis, as well as the role of B-cells and other cells bridging innate and adaptive immunity, contributes to novel insights into the mechanistic pathways influencing disease resolution or chronicity. Hopefully, new perspectives and state-of-the-art technology will help to shed light on the still-elusive enigma of sarcoid aetiology. This perspective article highlights a number of recent advances in the search for antigenic targets in sarcoidosis, as well as the main arguments for sarcoidosis as a spectrum of autoimmune conditions, either as a result of an external (microbial) trigger and/or due to defective control mechanisms regulating the balance between T-cell activation and inhibition.

Sarcoidosis and autoimmune diseases: differences, similarities and overlaps

PURPOSE OF REVIEW

Sarcoidosis is a rare, multisystem granulomatous disease of incompletely understood pathogenesis. Clinically, it shares common features with several systemic and organ-specific autoimmune diseases, although known autoantibodies or useful serologic markers for diagnosis and monitoring of disease activity are lacking. Sarcoidosis can both coexist with or mimic connective tissue diseases or vasculitis. Here, we review possible common etiologic factors between sarcoidosis and autoimmune disease, comparing clinical, laboratory and imaging features.

RECENT FINDINGS

Autoimmune diseases may precede or follow the diagnosis of sarcoidosis. Overall, the prevalence of both co-existing is unknown because of limited evidence. The presence of autoantibodies in sarcoidosis should raise suspicion of an underlying autoimmune disease that mimics or co-occurs with sarcoidosis. Silica dust exposure has been associated with an increased prevalence of both sarcoidosis and rheumatoid arthritis. In another study, autoimmune thyroid disease, Sjogren's syndrome and ankylosing spondylitis have been reported to be more frequent in sarcoidosis compared with healthy controls.

SUMMARY

A systematic diagnostic work-up is necessary to detect overlapping disease features in patients with sarcoidosis. Immune-modulating therapies need to be taken into account as these can induce paradoxical reactions.

Sarcoidosis and the Liver

Hepatic granulomas are a common finding in systemic sarcoidosis, but most patients remain asymptomatic. Elevated alkaline phosphatase is the most common sign of hepatic sarcoidosis (HS). Lacking a specific diagnostic test, the diagnosis of HS is one of exclusion. Therapy may be indicated in a minority of patients to control symptoms, but the effects of therapy in the natural history of HS are unknown.

The composition of the pulmonary microbiota in sarcoidosis - an observational study

Background

Sarcoidosis is a systemic disease of unknown etiology. The disease mechanisms are largely speculative and may include the role microbial patterns that initiate and drive an underlying immune process. The aim of this study was to characterize the microbiota of the lung of patients with sarcoidosis and compare its composition and diversity with the results from patients with other interstitial lung disease (ILD) and historic healthy controls.

Methods

Patients (sarcoidosis, n = 31; interstitial lung disease, n = 19) were recruited within the PULMOHOM study, a prospective cohort study to characterize inflammatory processes in pulmonary diseases. Bronchoscopy of the middle lobe or the lingula was performed and the recovered fluid was immediately sent for analysis of the pulmonary microbiota by 16sRNA gene sequencing. Subsequent bioinformatic analysis was performed to compare the groups.

Results

There were no significant differences between patients with sarcoidosis or other ILDs with regard to microbiome composition and diversity. In addition, the abundance of the genera Atopobium, Fusobacterium, Mycobacterium or Propionibacterium were not different between the two groups. There were no gross differences to historical healthy controls.

Conclusion

The analysis of the pulmonary microbiota based on 16sRNA gene sequencing did not show a significant dysbiosis in patients with sarcoidosis as compared to other ILD patients. These data do not exclude a microbiological component in the pathogenesis of sarcoidosis.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1013-2) contains supplementary material, which is available to authorized users.

In Situ Humoral Immunity to Vimentin in HLA-DRB1*03+ Patients With Pulmonary Sarcoidosis

Vimentin has been implicated in pulmonary sarcoidosis as a T-cell autoantigen, particularly in the context of HLA-DRB1*03, the Vα2.3/Vβ22 T-cell receptor (TCR), and Löfgren’s syndrome. As vimentin is a known antigenic target in B-cell-mediated autoimmunity, we investigated in situ humoral anti-vimentin responses in pulmonary sarcoidosis and their relationship with HLA-DRB1*03. Sarcoid and healthy control (HC) lung biopsies were analyzed by multi-color confocal microscopy for B-cells, T-cells, proliferation, and vimentin, and compared to tonsillectomy tissue. Bronchoalveolar lavage fluid (BALF) and serum from 48 sarcoidosis patients and 15 healthy volunteers were typed for HLA-DRB1*03 and titrated for antibodies to full-length vimentin, vimentin truncations, and total IgG and IgA by ELISA. Presence of extracellular vimentin in BALF was determined by mass spectrometry and T-cell populations measured by flow cytometry. Sarcoid lung samples, especially from HLA-DRB1*03⁺ patients, contained vimentin-rich tertiary lymphoid structures and corresponding BALF was highly enriched for both IgG and IgA anti-vimentin antibody (AVA) titers. Furthermore, sarcoidosis patient BALF AVA concentrations (expressed as arbitrary units per milligram of total immunoglobulin isotype) correlated with the percentage of CD4⁺ T-cells expressing the Vα2.3/Vβ22 TCR. BALF antibody reactivity to the vimentin N-terminus was most prominent in HCs, whereas reactivity to the C-terminus (Vim_C-term) was enriched in the sarcoid lung. Specifically, HLA-DRB1*03⁺ patient BALF contained higher concentrations of anti-Vim_C-term antibodies than BALF from both HCs and HLA-DRB1*03⁻ patients. Consistent with the lung as a site of AVA production, the concentration of AVAs in BALF was dramatically higher than in matched serum samples. Overall, there was a poor correlation between BALF and serum AVA concentrations. Together, these studies reveal the presence of linked in situ recognition of vimentin by both T- and B-cells in HLA-DRB1*03⁺ sarcoidosis patients, associated with a selective humoral immune response to the vimentin C-terminus.

The Pathogenesis of Pulmonary Sarcoidosis and Implications for Treatment

Thoracic sarcoidosis is the most common form of sarcoidosis, encompassing a heterogeneous group of patients with a wide range of clinical features and associated outcomes. The distinction between isolated thoracic lymphadenopathy and pulmonary involvement matters. Morbidity is often higher, and long-term outcomes are worse for the latter. Although inflammatory infiltrates in pulmonary sarcoidosis may resolve, persistent disease activity is common and can result in lung fibrosis. Given the distinct clinical features and natural history of pulmonary sarcoidosis, its pathogenesis may differ in important ways from other sarcoidosis manifestations. This review highlights recent advances in the pathogenesis of pulmonary sarcoidosis, including the nature of the sarcoidosis antigen, the role of serum amyloid A and other host factors that contribute to alterations in innate immunity, factors that shape adaptive T-cell profiles in the lung, and how these mechanisms influence the maintenance of granulomatous inflammation in sarcoidosis. We discuss questions raised by recent findings, including the role of innate immunity in the pathogenesis, the meaning of immune cell exhaustion, and mechanisms that may contribute to lung fibrosis in sarcoidosis. We conclude with a reflection on when and how immunosuppressive therapies may be helpful for pulmonary sarcoidosis, a consideration of nonpharmacologic management strategies, and a survey of potential novel therapeutic targets for this vexing disease.