The Etiologic Role of Infectious Antigens in Sarcoidosis Pathogenesis

Pathogenetic Mechanisms Linking Sarcoidosis to Lymphoma

Sarcoidosis and lymphoma share immunopathological characteristics that suggest a complex, interconnected relationship. This article examines the multi-faceted mechanisms linking sarcoidosis to lymphoma, a phenomenon called sarcoidosis-lymphoma syndrome (SLS). SLS is hard to diagnose, requiring distinct criteria and imaging to differentiate overlapping features and histological differences. The co-occurrence of these diseases may be explained by genetic predispositions, immune dysregulation, and environmental factors that enhance malignancy risk. In active sarcoidosis, chronic inflammation and granuloma formation induce the production of cytokines that can contribute to lymphoma development. The role of macrophage polarization is also discussed. Immunosuppressive treatment prescribed in sarcoidosis patients, particularly corticosteroids and biological agents, may increase the susceptibility to lymphoproliferative malignancies. These common mechanisms emphasize the need for vigilant monitoring of lymphoma in patients with sarcoidosis, as this granulomatous disease can mimic and promote the development of lymphoma.

Application of laboratory models for sarcoidosis research

This manuscript will review the implications and applications of sarcoidosis models towards advancing our understanding of sarcoidosis disease mechanisms, identification of biomarkers, and preclinical testing of novel therapies. Emerging disease models and innovative research tools will also be considered.

Air pollution and incident sarcoidosis in central Pennsylvania

Sarcoidosis is a chronic granulomatous disease predominantly affecting the lungs and inducing significant morbidity and elevated mortality rate. The etiology of the disease is unknown but may involve exposure to an antigenic agent and subsequent inflammatory response resulting in granuloma formation. Various environmental and occupational risk factors have been suggested by previous observations, such as moldy environments, insecticides, and bird breeding. Our study investigated the association of air pollution with diagnosis of sarcoidosis using a case-control design. Penn State Health electronic medical records from 2005 to 2018 were examined for adult patients with (cases) and without (controls) an International Classification of Disease (ICD)-9 or -10 code for sarcoidosis. Patient addresses were geocoded and 24-hr residential-level air pollution concentrations were estimated using spatio-temporal models of particulate matter <2.5 μm (PM2.5), ozone, and PM2.5 elemental carbon (EC) and moving averages calculated. In total, 877 cases and 34,510 controls were identified. Logistic regression analysis did not identify significant associations between sarcoidosis incidence and air pollution exposure estimates. However, the odds ratio (OR) for EC for exposures occurring 7-10 years prior did approach statistical significance, and ORs exhibited an increasing trend for longer averaging periods. Data suggested a latency period of more than 6 years for PM2.5 and EC for reasons that are unclear. Overall, results for PM2.5 and EC suggest that long-term exposure to traffic-related air pollution may contribute to the development of sarcoidosis and emphasize the need for additional research and, if the present findings are substantiated, for public health interventions addressing air quality as well as increasing disease surveillance in areas with a large burden of PM2.5 and EC.

Comparison between diffuse and partial involvement of thoracic lymph nodes on the outcome of sarcoidosis patients

BACKGROUND AND AIM

Sarcoidosis is a systemic disease of unknown etiology with diverse clinical manifestations. Disease may resolve spontaneously or require immunosuppression to control progression. Currently, there is no predictive model to direct treatment, and management is guided by symptoms and functional impairment. This study examines the association between biopsy features and prognosis.

METHODS

This is a retrospective population-based cohort study. New cases of biopsy-proven sarcoidosis were divided into two groups: those with diffuse thoracic lymph nodes (TLN) involvement, versus partial TLN involvement (Defined as Non-necrotizing granuloma (NNG) found in some but not all sampled TLN). We compared outcomes one year after diagnosis. We assessed the need for immunosuppression, the number of hospitalizations, and lung function deterioration.

RESULTS

77 cases were included in the final analysis. 48.1% demonstrated extensive TLN involvement, and 51.9% demonstrated partial or non-involvement of sampled TLN. The partial positive group had a more aggressive disease, reflected by a significantly higher need for steroid therapy in the first year after diagnosis (45.0% vs. 18.9% p=0.015). The number of hospitalizations and lung functions were not significantly different between groups.

CONCLUSIONS

Our findings demonstrate a significantly increased need for steroidal therapy among sarcoidosis patients with a partial positivity of TLN. These findings suggest that the degree of TLN involvement can help predict worse outcome and guide therapeutic decisions.

Sarcoidosis following COVID infection: A case series

Here we describe three cases of sarcoidosis which were diagnosed following COVID infection. Treating clinicians should consider post-COVID-19 sarcoidosis in their differential, as it represents a potentially treatable cause of persistent symptomatology.

Genetics of neurosarcoidosis

Sarcoidosis is a systemic, inflammatory, granulomatous disease characterized by great variability in organ involvement, clinical course, and severity. While pulmonary manifestations are almost universal, the central and peripheral nervous systems can also be affected. Neurosarcoidosis occurs in ∼5-15% of cases and is among the manifestations with the highest morbidity and mortality. It is known that sarcoidosis has genetic underpinnings and while multiple studies aimed at identifying associations to sarcoidosis susceptibility and prognosis, very few studies have focused on neurosarcoidosis. This review summarizes the genetic studies to date, compares and contrasts those findings with other genetic effects in sarcoidosis, and offers ideas for moving the field forward.

A Case of Thrombotic Microangiopathy and Acute Sarcoidosis

Although sarcoidosis is an established cause of multiorgan dysfunction, acute presentation with thrombotic microangiopathy resulting in severe renal and hematological sequelae has not been reported. We describe the case of a patient presenting with hypercalcemia, pancreatitis, and acute renal failure, followed by microangiopathic hemolytic anemia. Although there were no significant respiratory symptoms, thoracic radiology and mediastinal lymph node biopsy results were in keeping with sarcoidosis as the underlying cause of this multisystem presentation. Corticosteroids were commenced with clinical and biochemical improvement. This novel case highlights the need to consider sarcoidosis as part of the differential diagnosis for unusual multiorgan presentations and for early multidisciplinary involvement in such cases to permit optimal treatment.

Sarcoidosis following SARS‐CoV ‐2 infection: Cause or consequence?

The COVID‐19 pandemic has been a worldwide medical challenge. Despite rapid advancements, many questions regarding SARS‐CoV‐2 interaction with other pathologies and long‐term consequences remained unanswered. Sarcoidosis is a multi‐systemic granulomatous disease that develops in genetically predisposed individuals following their exposure to an environmental trigger. We present the case of a patient who was diagnosed with sarcoidosis following a SARS‐CoV‐2 infection.

CD31+, CD38+, CD44+, and CD103+ lymphocytes in peripheral blood, bronchoalveolar lavage fluid and lung biopsy tissue in sarcoid patients and controls

Background

The mechanisms driving the transition from inflammation to fibrosis in sarcoidosis patients are poorly understood; prognostic features are lacking. Immune cell profiling may provide insights into pathogenesis and prognostic factors of the disease. This study aimed to establish associations in simultaneous of lymphocyte subset profiles in the blood, bronchoalveolar lavage fluid (BALF), and lung biopsy tissue in the patients with newly diagnosed sarcoidosis.

Methods

A total of 71 sarcoid patients (SPs) and 20 healthy controls (HCs) were enrolled into the study. CD31, CD38, CD44, CD103 positive T lymphocytes in blood and BALF were analysed. Additionally, the densities of CD4, CD8, CD38, CD44, CD103 positive cells in lung tissue biopsies were estimated by digital image analysis.

Results

Main findings: (I) increase of percentage of CD3⁺CD4⁺CD38⁺ in BALF and blood, and increase of percentage of CD3⁺CD4⁺CD44⁺ in BALF in Löfgren syndrome patients comparing with patients without Löfgren syndrome, (II) increase of percentage of CD3⁺CD4⁺103⁺ in BALF and in blood in patients without Löfgren syndrome (comparing with Löfgren syndrome patients) and increase of percentage of CD3⁺CD4⁺103⁺ in BALF and in blood in more advanced sarcoidosis stage. (III) Increasing percentage of BALF CD3⁺CD4⁺CD31⁺ in sarcoidosis patients when comparing with controls independently of presence of Löfgren syndrome, smoking status or stage of sarcoidosis. Several significant correlations were found.

Conclusions

Lymphocyte subpopulations in blood, BALF, and lung tissue were substantially different in SPs at the time of diagnosis compared to HCs. CD3⁺CD4⁺CD31⁺ in BALF might be a potential supporting marker for the diagnosis of sarcoidosis. CD3⁺CD4⁺CD38⁺ in BALF and blood and CD3⁺CD4⁺CD44⁺ in BALF may be markers of the acute immune response in sarcoidosis patients. CD4⁺CD103⁺ T-cells in BALF and in blood are markers of the persistent immune response in sarcoidosis patients and are potential prognostic features of the chronic course of this disease.

Chest Imaging of Patients with Sarcoidosis and SARS-CoV-2 Infection. Current Evidence and Clinical Perspectives

The recent COVID-19 pandemic has dramatically changed the world in the last months, leading to a serious global emergency related to a novel coronavirus infection that affects both sexes of all ages ubiquitously. Advanced age, cardiovascular comorbidity, and viral load have been hypothesized as some of the risk factors for severity, but their role in patients affected with other diseases, in particular immune disorders, such as sarcoidosis, and the specific interaction between these two diseases remains unclear. The two conditions might share similar imaging findings but have distinctive features that are here described. The recent development of complex imaging softwares, called deep learning techniques, opens new scenarios for the diagnosis and management.

Potential use of biomarkers for the clinical evaluation of sarcoidosis

Sarcoidosis is a systemic granulomatous disease of unknown etiology and pathogenesis with a heterogeneous clinical presentation. In the appropriate clinical and radiological context and with the exclusion of other diagnoses, the disease is characterized by the pathological presence of non-caseating epithelioid cell granulomas. Sarcoidosis is postulated to be a multifactorial disease caused by chronic antigenic stimulation. The immunopathogenesis of sarcoidosis encompasses a complex interaction between the host, genetic factors and postulated environmental and infectious triggers, which result in granuloma development.The exact pathogenesis of the disease has yet to be elucidated, but some of the inflammatory pathways that play a key role in disease progression and outcomes are becoming apparent, and these may form the logical basis for selecting potential biomarkers.Biomarkers are biological molecules that are altered pathologically. To date, there exists no single reliable biomarker for the evaluation of sarcoidosis, either diagnostically or prognostically but new candidates are emerging. A diagnosis of sarcoidosis ideally requires a biopsy confirming non-caseating granulomas, but the likelihood of progression that requires intervention remains unpredictable. These challenging aspects could be potentially resolved by incorporating biomarkers into clinical practice for both diagnosis and monitoring disease activity.This review outlines the current knowledge on sarcoidosis with an emphasis on pulmonary sarcoidosis, and delineates the understanding surrounding the implication of biomarkers for the clinical evaluation of sarcoidosis.

Current Sarcoidosis Models and the Importance of Focusing on the Granuloma

The inability to effectively model sarcoidosis in the laboratory or in animals continues to hinder the discovery and translation of new, targeted treatments. The granuloma is the signature pathological hallmark of sarcoidosis, yet there are significant knowledge gaps that exist with regard to how granulomas form. Significant progress toward improved therapeutic and prognostic strategies in sarcoidosis hinges on tractable experimental models that recapitulate the process of granuloma formation in sarcoidosis and allow for mechanistic insights into the molecular events involved. Through its inherent representation of the complex genetics underpinning immune cell dysregulation in sarcoidosis, a recently developed in vitro human granuloma model holds promise in providing detailed mechanistic insight into sarcoidosis–specific disease regulating pathways at play during early stages of granuloma formation. The purpose of this review is to critically evaluate current sarcoidosis models and assess their potential to progress the field toward the goal of improved therapies in this disease. We conclude with the potential integrated use of preclinical models to accelerate progress toward identifying and testing new drugs and drug combinations that can be rapidly brought to clinical trials.

Trace Elements in the Lung Tissue Affected by Sarcoidosis

In the lungs of 76 patients with verified sarcoidosis, 28 chemical elements were identified with neutron activation analysis. High levels of Ca, Fe, Cr, Co, Cs, Eu, Lu, Th, Hf, Au, and U and low level of Na compared to the control samples were determined in sarcoidosis. There were no significant differences in the content of Zn, Rb, La, Sm, Sr, Nd, As, Br, Ag, Tb, Sc, Ta, Sb, Ba, and Yb. Spearman correlation analysis shows multiple positive associations, with the maximum being in pairs as follows: Fe-Cr, Eu-La, Ce-Lu, Hf-Cr, Sc-Zn, Fe-Hf, Ce-Co, and Sb-Cr. These studies support the hypothesis that sarcoidosis is a response of the organism in the form of granulomatous inflammation when exposed to heavy metals and rare earth elements in the environment. We assume that the role of calcium and iron is to separate granulomas from the tissues of the body.

The presence of mycobacterial antigens in sarcoidosis associated granulomas

Background: Sarcoidosis is a multi-organ disorder with unknown etiology. The role of bacteria in pathogenesis of sarcoidosis is still controversial. This study analyses new aspects of Mycobacterium Tuberculosis (MTB) presence in sarcoidosis diseases. Objectives: To find MTB in paraffin embedded tissues of sarcoidosis patients, samples of 10 sarcoidosis, 12 confirmed pulmonary tuberculosis (PTB) and 5 controls associated with granulomatous tissues were analysed. Methods: The paraffin embedded tissue specimens of the selected patients from the pathology archive of a subspecialty pulmonary hospital in IRAN were evaluated by Real Time PCR for MTB DNA using IS6110. Immunohistochemistry (IHC) method using MTB purified protein derivative (PPD) antibody was used to detect mycobacterial antigens. Results: All sarcoidosis patients had negative MTB DNA results in Real time PCR analysis. This analysis resulted in 10 (83.3%) positive cases for TB patients. The IHC analysis for MTB anti-PPD antibody showed positive diffused cytoplasmic staining for all TB patients whereas this staining was positive for 3 sarcoidosis patients (30%). Conclusion: Amplification of the IS6110 DNA sequence that is the most common target used for MTB diagnosis is not sensitive method to detect MTB in sarcoidosis granuloma. However, tissue IHC for anti-PPD antibody shows higher performance to detect MTB in sarcoidal granulomas reveals a mycobacterial signature in sarcoidosis tissue with negative IS6110 assay. This finding supports Mycobacterium tuberculosis may have an etiologic role in sarcoidosis. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 236-241)

Non-infectious granulomatous dermatoses

Granulomatous dermatoses comprise a wide range of etiologically and clinically distinct skin diseases that share a common histology characterized by the accumulation of histiocytes include macrophages. While the pathogenesis of these disorders is not fully understood, the underlying mechanism is thought to involve a reaction pattern caused by an immunogenic stimulus. Antigen-presenting cells and the effect of various cytokines play a key role. Our understanding of granulomatous reaction patterns has been advanced by insights drawn from observations of such reactions in patients on immunomodulatory therapy and in individuals with genetic immunodeficiency. Traditionally, a distinction is made between infectious and non-infectious granulomatous dermatoses. The present CME article addresses granulomatous skin diseases for which there is no evidence of a causative infectious agent. Common representatives include granuloma annulare, necrobiosis lipoidica and cutaneous sarcoidosis. Granulomatous dermatoses may be part of the clinical spectrum of various systemic disorders or may be associated therewith. Some neoplastic disorders may mimic granulomatous dermatoses histologically. Given the pathogenetic diversity involved, the clinical presentation, too, is quite varied. Overall, however, each disorder is characterized by typical clinical features. The diagnosis always requires thorough clinicopathologic correlation. Treatment is preferably based on the underlying pathogenesis and frequently involves anti-inflammatory agents. In most cases, however, there is insufficient study data. The dermal nature of these disorders frequently poses a therapeutic challenge, especially with respect to topical treatment.

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.

PET/CT Imaging in Soft Tissue Infection and Inflammation-An Update

Nuclear medicine procedures, including Ga-67 and labeled leucocyte SPECT/CT as well as PET/CT using 18F-FDG and recently Ga-68 tracers, have found extensive applications in the assessment of infectious and inflammatory processes in general and in soft tissues in particular. Recent published data focus on summarizing the available imaging information with the purpose of providing the referring clinicians with optimized evidence based results. Guidelines and/or recommendations of clinical societies have incorporated nuclear medicine tests (using both labeled leucocytes and FDG) in their suggested work-up for evaluation of infective endocarditis and in certain patients with suspected vascular graft infections. Joint guidelines of the European and American nuclear medicine societies include fever of unknown origin, sarcoidosis, and vasculitis among the major clinical indications that will benefit from nuclear medicine procedures, specifically from FDG PET/CT. Limitations and pitfalls for the use of radiotracers in assessment of infection and inflammation can be related to patient conditions (eg, diabetes mellitus), or to the biodistribution of a specific radiopharmaceutical. Limited presently available data on the use of functional and/or metabolic monitoring of response to infectious and inflammatory processes to treatment and with respect to the effect of drugs such as antibiotics and glucocorticoids on the imaging patterns of these patients need further confirmation.

Respiratory muscles dysfunction and respiratory diseases

This review presents an analysis of the literature on the topic of respiratory muscle (RM) dysfunction in various forms of respiratory pathology: chronic obstructive pulmonary disease (COPD), asthma, community-acquired pneumonia, idiopathic pulmonary fibrosis (IPF), sarcoidosis and interstitial lung diseases (ILD), associated with systemic connective tissue diseases (polymyositis, dermatomyositis and systemic lupus erythematosus - SLE). Various clinical and pathophysiological aspects of RM dysfunction and general patterns of its pathogenesis were examined. It was proved that the role of RM in the development of respiratory failure depends on the form and stage of the pulmonary pathology and the severity of systemic manifestations of these diseases: excessive proteolysis, oxidative stress, hypoxia, chronic systemic inflammation. These factors modify the morphofunctional status of RM, worsens their contractile function, which is contributed to the development of respiratory failure. In some cases, the primary weakness of RM precedes the clinical manifestation of pulmonary pathology, which is distinctive for some variants of myositis-associated ILD and SLE. Endogenous intoxication syndrome plays a significant role in the development of RM dysfunction during community-acquired pneumonia. It is noted that sarcoid pulmonary ventilation disorders associate with the RM weakness, but not with the degree of lung damage. In most cases, secondary RM dysfunction predominates that contributes to respiratory failure progression, which is especially noticeable in case of COPD, asthma and IPF.

Trained Innate Immunity Not Always Amicable

The concept of &bdquo;trained innate immunity" is understood as the ability of innate immune cells to remember invading agents and to respond nonspecifically to reinfection with increased strength. Trained immunity is orchestrated by epigenetic modifications leading to changes in gene expression and cell physiology. Although this phenomenon was originally seen mainly as a beneficial effect, since it confers broad immunological protection, enhanced immune response of reprogrammed innate immune cells might result in the development or persistence of chronic metabolic, autoimmune or neuroinfalmmatory disorders. This paper overviews several examples where the induction of trained immunity may be essential in the development of diseases characterized by flawed innate immune response.

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.

Sarcoidosis deaths in the United States: 1999-2016

BACKGROUND

It has been over a decade since a comprehensive study has been published that has examined sarcoidosis deaths at the national level. The purpose of this study was to analyze sarcoidosis as the underlying cause of death using current national death certificate data. Results from this project can be used to evaluate and compare trends of sarcoidosis reported deaths across the U.S.

METHODS

Mortality data from 1999 to 2016 were provided by the National Vital Statistics System (NVSS) with sarcoidosis (ICD-D86.X) as the underlying cause of death from all resident death certificates filed in the 50 states and the District of Columbia (DC). Data were analyzed using CDC WONDER, a web-based public health database and analysis tool. Queries were used to generate number of deaths, along with unadjusted and age-adjusted death rates with 95% confidence intervals and standard errors for groups including year, census region, gender, age group, race/ethnicity and state. Joinpoint regression analysis was used to test the significance of trends in race and gender-specific rates for the 1999-2016 study period.

RESULTS

From 1999 to 2016, there were a total of 16,665 sarcoidosis reported deaths in the U.S. The overall age-adjusted mortality rate increased from 2.1 (deaths per 1,000,000) in 1999 to 3.1 in 2002, but then remained relatively stable thereafter until the end of the study period. Female deaths increased 32.0% (from 2.5 to 3.3 per 1,000,000), while male deaths increased 73.3% (from 1.5 to 2.6 deaths per 1,000,000). The highest age-adjusted death rates were among black females (17.0 deaths per 1,000,000), and black males (12.4 deaths per 1,000,000). At the regional level, the southern U.S. had the highest overall mean age-adjusted mortality rate (3.7 deaths per 1,000,000), while black females in the Midwest (18.7 per 1,000,000) had the highest race-specific reported death rate.

DISCUSSION

The detected increase in the total number of deaths and age-adjusted rates of sarcoidosis deaths in the U.S. is a serious health concern. Factors that contribute to sarcoidosis deaths remain uncertain and more epidemiological research studies are needed to compliment current bench science to explore and examine factors that contribute to this multifactorial, chronic disease.

A new model for chronic diseases

Chronic diseases are defined diseases whose symptoms last for at least six months and tend to worsen over time. In Europe, they cause at least 86% of deaths. In this speculative unifying model I set a new hypothesis for the etiology of the majority of chronic diseases. The main aim is to put order and observe our organism in a systemic way, connecting pathologies we now see as disconnected phenomena, with the conceptual frameworks of complex systems and network medicine. Chronic diseases could be caused by a first unsolved acute infection. In case the pathogen cannot be completely eliminated, it becomes a persistent infectious. After the acute episode, some mild symptoms will occur and probably disappear; the chronic disease will remain latent over time. It will manifest even after years or decades, in the presence of another acute infection, a particular stress, trauma, or another event. The presence of the persistent infectious elicits changes in the immune and systemic regulation, and these processes degenerate over time. They will assume their rules and patterns, being independent from the initial stimulus. The key to understand the dynamics and individuality of chronic diseases is the immune system and its networks. The immune mechanisms that can lead to the persistent response are mainly the switch from the Th1 to the Th2 immunity and the molecular mimicry. The first persistent infectious will also modify the susceptibility to other pathogens, facilitating new infections and new consequent persistent infectious. From the immune point of view, our organism is divided into three compartments: the outer one, which comprehend all the surfaces in contact with the environment, the intermediate one, which comprehend the internal organs and tissues, and the innermost one, comprehending the Central Nervous System and the adluminal compartment of the seminiferous tubule. The immune key-role is played respectively by the mucosa-associated lymphoid tissue, the endothelium, the blood-brain barrier and blood-testis barrier. The chronic diseases follow a progressive scheme, involving the three compartments from the outer to the innermost one. The primer microorganism at the origin of the majority of diseases could be streptococcus, or staphylococcus. Both cause acute in children, with a great variability of responses and symptoms, and both cause molecular mimicry. This model can be tested and proved in more ways, I propose here some of them. It could pave the way to a radical change in our comprehension and therapeutic approaches to chronic diseases.

Propionibacterium acnes-derived insoluble immune complexes in sinus macrophages of lymph nodes affected by sarcoidosis

Background

Propionibacterium acnes is thought to be a causative agent of sarcoidosis. Patients with sarcoidosis have circulating immune complexes. We attempted to detect P. acnes-derived immune complexes in sarcoid lesions.

Methods

We evaluated formalin-fixed and paraffin-embedded lymph node samples from 38 sarcoidosis patients and 90 non-sarcoidosis patients (27 patients with necrotizing lymphadenitis, 28 patients with reactive lymphadenitis, 16 patients with colon cancer, 19 patients with gastric cancer) by immunohistochemistry using anti-human immunoglobulins (IgG, IgA, and IgM) and complement (C1q and C3c) antibodies, and a P. acnes-specific monoclonal antibody (PAB antibody) that reacts with the membrane-bound lipoteichoic acid of P. acnes.

Results

Small round bodies (SRBs) bound to IgA, IgM, or IgG were detected in sinus macrophages, in 32 (84%), 32 (84%), or 11 (29%) sarcoid samples, respectively, and in 19 (21%), 26 (29%), or no (0%) control samples, respectively. Some of these insoluble immune complexes (IICs) also bound to C1q and C3c. We developed a microwave treatment followed by brief trypsin digestion (MT treatment) to detect PAB-reactive SRBs bound to immunoglobulins (IIC-forming P. acnes). MT treatment revealed abundant IIC-forming P. acnes in most (89%) of the sarcoid samples and sparse distribution in some (20%) of the control samples with lymphadenitis, but no IIC-forming P. acnes was detected in control samples without inflammation. IIC-forming P. acnes were mostly bound to both IgA and IgM. The PAB-reactive antigen and immunoglobulins were both located at the peripheral rim of the IIC-forming P. acnes. Conventional electron microscopy identified many SRBs (0.5–2.0 μm diameter) in sinus macrophages of sarcoid lymph nodes with many IIC-forming P. acnes, some of which were in phagolysosomes with a degraded and lamellar appearance.

Conclusions

P. acnes-derived IICs in sinus macrophages were frequent and abundant in sarcoid lymph nodes, suggesting a potential etiologic link between sarcoidosis and this commensal bacterium.

Sarcoidosis in A. C. Milan (1899)?

The pathogenesis, diagnosis and therapy of sarcoidosis as an autonomous disease are subjects of spirited discussions, which haven’t found definitive conclusion yet. Distinguishing between sarcoidosis and sarcoid-like reactions (sarcoid - type granulomas) is not currently a medical “gold standard” and is not implemented in clinical practice. This leads to 1) misinterpretation of numerous available data; 2) difficulty in the interpretation of other unverified data, which is often followed by 3) inappropriate or inadequate therapeutic approach. Similarly to many other diseases, in sarcoidosis and sarcoid - types of reactions the concept of personalised approach and therapy should also be introduced. This methodology of clinical guidance is difficult, complex and not always achievable in the current medical status and relations (doctor-patient relationship; financial factor; time factor). It is appropriate to note that in some cases the guidelines or the so-called standards are neglected or not possible to put into practice with the aim of better therapeutic practices and strategies, as well as the achievement of optimal final clinical results (especially in patients with sarcoid granulomas). The sarcoid granuloma, even when it is sterile, should not be considered as the equivalent of sarcoidosis, i.e., sarcoidosis as an autonomous disease. Sure enough, exactly because of this fact, the personalised approach should not be an exception, but it has to gradually become a rule in medical practice. When clinical decisions are conformed to some of the latest modern concepts, officialised in the international databases, often the achieved results can be much better.

We present a patient with a tattoo of AC Milan (1899) on his right arm, who subsequently developed localised sterile sarcoid granulomas in the area of the tattoo. Later the process became generalised on his whole body’s skin, lungs and lymph nodes. It is unclear for the moment whether this condition should be interpreted as sarcoidosis as an autonomous disease or, instead, as a sarcoidal type of reaction with subsequent generalisation due to cross-reactivity against antigens present in other tissues with similarities to the exogenous pigments. Following the modern concepts regarding the pathogenesis of these two conditions, we introduced, in this case, an innovative, non-standard approach: 1) systemic and local immunosuppressive therapy, combined with 2) recommеndation for immediate surgical excision of the tattoo to remove the possible trigger of molecular and antigen mimicry.

T-cell immunology in sarcoidosis: Disruption of a delicate balance between helper and regulatory T-cells

PURPOSE OF REVIEW

Although the aetiology of sarcoidosis is not yet completely understood, immunological changes within the T-cell compartment are characteristic for an exaggerated antigen-driven immune response. In this review, we describe the most recent findings on T-cell subset responses and regulation in sarcoidosis. We discuss how future immunological research can advance the field to unravel pathobiological mechanisms of this intriguingly complex disease.

RECENT FINDINGS

Research into the field of T-cell plasticity has recently challenged the long-held T helper type 1 (Th1) paradigm in sarcoidosis and striking parallels with autoimmune disorders and common variable immunodeficiency were recognized. For instance, it was demonstrated that Th17.1-cells rather than Th1-cells are responsible for the exaggerated IFN-γ production in pulmonary sarcoidosis. Furthermore, impaired regulatory T-cell function and alterations within the expression of co-inhibitory receptors that control T-cell responses, such as PD-1, CTLA-4 and BTNL2, raise new questions regarding T-cell regulation in pulmonary sarcoidosis.

SUMMARY

It becomes increasingly clear that Th17(.1)-cells and regulatory T-cells are key players in sarcoidosis T-cell immunology. New findings on plasticity and co-inhibitory receptor expression by these subsets help build a more comprehensive model for T-cell regulation in sarcoidosis and will finally shed light on the potential of new treatment modalities.

High throughput 16SrRNA gene sequencing reveals the correlation between Propionibacterium acnes and sarcoidosis

Objective

This study aims to use high throughput 16SrRNA gene sequencing to examine the bacterial profile of lymph node biopsy samples of patients with sarcoidosis and to further verify the association between Propionibacterium acnes (P. acnes) and sarcoidosis.

Methods

A total of 36 mediastinal lymph node biopsy specimens were collected from 17 cases of sarcoidosis, 8 tuberculosis (TB group), and 11 non-infectious lung diseases (control group). The V4 region of the bacterial 16SrRNA gene in the specimens was amplified and sequenced using the high throughput sequencing platform MiSeq, and bacterial profile was established. The data analysis software QIIME and Metastats were used to compare bacterial relative abundance in the three patient groups.

Results

Overall, 545 genera were identified; 38 showed significantly lower and 29 had significantly higher relative abundance in the sarcoidosis group than in the TB and control groups (P < 0.01). P. acnes 16SrRNA was exclusively found in all the 17 samples of the sarcoidosis group, whereas was not detected in the TB and control groups. The relative abundance of P. acnes in the sarcoidosis group (0.16% ± 0. 11%) was significantly higher than that in the TB (Metastats analysis: P = 0.0010, q = 0.0044) and control groups (Metastats analysis: P = 0.0010, q = 0.0038). The relative abundance of P. granulosum was only 0.0022% ± 0. 0044% in the sarcoidosis group. P. granulosum 16SrRNA was not detected in the other two groups.

Conclusion

High throughput 16SrRNA gene sequencing appears to be a useful tool to investigate the bacterial profile of sarcoidosis specimens. The results suggest that P. acnes may be involved in sarcoidosis development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0515-z) contains supplementary material, which is available to authorized users.

Humoral immune profiling of mycobacterial antigen recognition in sarcoidosis and Löfgren's syndrome using high-content peptide microarrays

INTRODUCTION

Sarcoidosis is considered an idiopathic granulomatous disease, although similar immunological and clinical features with tuberculosis (TB) suggest mycobacterial involvement in its pathogenesis. High-content peptide microarrays (HCPM) may help to decipher mycobacteria-specific antibody reactivity in sarcoidosis.

METHODS

Serum samples from patients with sarcoidosis, Löfgren's syndrome, and TB, as well as from healthy individuals (12/group), were tested on HCPM containing 5964 individual peptides spanning 154 Mycobacterium tuberculosis proteins displayed as 15-amino acid stretches. Inclusion/exclusion and significance analyses were performed according to published methods.

RESULTS

Each study group recognized 68-78% M. tuberculosis peptides at least once. M. tuberculosis epitope recognition by sarcoidosis patient sera was 42.7%, and by TB patient sera was 39.1%. Seven and 16 peptides were recognized in 9/12 (75%) and 8/12 (67%) sarcoidosis patient sera but not in TB patient sera, respectively. Nine (75%) and eight (67%) out of twelve TB patient sera, respectively recognized M. tuberculosis peptides that were not recognized in sarcoidosis patient sera.

CONCLUSIONS

Specific IgG recognition patterns for M. tuberculosis antigens in sarcoidosis patients re-affirm mycobacterial involvement in sarcoidosis, providing biologically relevant targets for future studies pertaining to diagnostics and immunotherapy.