Dendritic cells in the pathogenesis of sarcoidosis

Advance in pathogenesis of sarcoidosis: Triggers and progression

Sarcoidosis, a multisystemic immune disease, significantly impacts patients' quality of life. The complexity and diversity of its pathogenesis, coupled with limited comprehensive research, had hampered both diagnosis and treatment, resulting in an unsatisfactory prognosis for many patients. In recent years, the research had made surprising progress in the triggers of sarcoidosis (genetic inheritance, infection and environmental factors) and the abnormal regulations on immunity during the formation of granuloma. This review consolidated the latest findings on sarcoidosis research, providing a systematic exploration of advanced studies on triggers, immune-related regulatory mechanisms, and clinical applications. By synthesizing previous discoveries, we aimed to offer valuable insights for future research directions and the development of clinical diagnosis and treatment strategies.

Integrative bioinformatics analysis to explore a robust diagnostic signature and landscape of immune cell infiltration in sarcoidosis

Background

The unknown etiology of sarcoidosis with variable clinical features leads to delayed diagnosis and limited therapeutic strategies. Hence, exploring the latent mechanisms and constructing an accessible and reliable diagnostic model of sarcoidosis is vital for innovative therapeutic approaches to improve prognosis.

Methods

This retrospective study analyzed transcriptomes from 11 independent sarcoidosis cohorts, comprising 313 patients and 400 healthy controls. The weighted gene co-expression network analysis (WGCNA) and differentially expressed gene (DEG) analysis were performed to identify molecular biomarkers. Machine learning was employed to fit a diagnostic model. The potential pathogenesis and immune landscape were detected by bioinformatics tools.

Results

A 10-gene signature SARDS consisting of GBP1, LEF1, IFIT3, LRRN3, IFI44, LHFPL2, RTP4, CD27, EPHX2, and CXCL10 was further constructed in the training cohorts by the LASSO algorithm, which performed well in the four independent cohorts with the splendid AUCs ranging from 0.938 to 1.000. The findings were validated in seven independent publicly available gene expression datasets retrieved from whole blood, PBMC, alveolar lavage fluid cells, and lung tissue samples from patients with outstanding AUCs ranging from 0.728 to 0.972. Transcriptional signatures associated with sarcoidosis revealed a potential role of immune response in the development of the disease through bioinformatics analysis.

Conclusions

Our study identified and validated molecular biomarkers for the diagnosis of sarcoidosis and constructed the diagnostic model SARDS to improve the accuracy of early diagnosis of the disease.

Novel insights in fibrotic pulmonary sarcoidosis

PURPOSE OF REVIEW

In chronic pulmonary sarcoidosis, the transition from the inflammatory to the fibrotic stage of the lungs occurs in about 10-20% of cases, eventually causing end-stage fibrotic disease. To date, pathogenetic mechanisms and clinical management remain challenging; thus, we highlight the recent evidence in pulmonary fibrotic processes, clinical signs for an early detection and the potential role of the current investigated antifibrotic agents and promising targeted therapies.

RECENT FINDINGS

Recent findings of relevant key cellular pathways can be considered as a glimmer of light in the complexity of sarcoidosis. In some patients, granulomas persist and serve as a nidus for fibrosis growth, sustained by several fibrosis-stimulating cytokines. Preclinical studies have detected profibrotic, antifibrotic and pleiotropic T cells as promoters of fibrosis. Epigenetics, genetics and transcriptomics research can lead to new target therapies. Antifibrotic drug nintedanib has shown a positive effect on non-idiopathic pulmonary fibrosis fibrotic lung diseases including fibrotic sarcoidosis; other antifibrotic drugs are under investigation.

SUMMARY

Pulmonary fibrosis strongly impacts the outcome of sarcoidosis, and a better understanding of the underlying pathogenic mechanisms can facilitate the development of novel treatments, improving clinical care and life expectancy of these patients. The greatest challenge is to investigate effective antifibrotic therapies once fibrosis develops. The role of these findings in fibrotic sarcoidosis can be translated into other interstitial lung diseases characterized by the coexistence of inflammatory and fibrotic processes.

Histology of Cardiac Sarcoidosis with Novel Considerations Arranged upon a Pathologic Basis

Sarcoidosis is a rare disease of isolated or diffuse granulomatous inflammation. Although any organs can be affected by sarcoidosis, cardiac sarcoidosis is a fatal disorder, and it is crucial to accurately diagnose it to prevent sudden death due to dysrhythmia. Although endomyocardial biopsy is invasive and has limited sensitivity for identifying granulomas, it is the only modality that yields a definitive diagnosis of cardiac sarcoidosis. It is imperative to develop novel pathological approaches for the precise diagnosis of cardiac sarcoidosis. Here, we aimed to discuss commonly used diagnostic criteria for cardiac sarcoidosis and to summarize useful and novel histopathologic criteria of cardiac sarcoidosis. While classical histologic observations including noncaseating granulomas and multinucleated giant cells (typically Langhans type) are the most important findings, others such as microgranulomas, CD68⁺ CD163^- pro-inflammatory (M1) macrophage accumulation, CD4/CD8 T-cell ratio, Cutibacterium acnes components, lymphangiogenesis, confluent fibrosis, and fatty infiltration may help to improve the sensitivity of endomyocardial biopsy for detecting cardiac sarcoidosis. These novel histologic findings are based on the pathology of cardiac sarcoidosis. We also discussed the principal histologic differential diagnoses of cardiac sarcoidosis, such as tuberculosis myocarditis, fungal myocarditis, giant cell myocarditis, and dilated cardiomyopathy.

Sarcoid-like reaction in a HER2-positive breast cancer patient: A case report

INTRODUCTION AND IMPORTANCE

Sarcoid-like reaction is a systemic granulomatous reaction that may develop in the lymph nodes and organs of cancer patients. Distinguishing a sarcoid-like reaction from metastasis is difficult. Accurate diagnosis of this reaction is key to preventing overtreatment.

CASE PRESENTATION

A 51-year-old woman presented with a lump in her left breast and swollen lymph nodes in her left axilla and infraclavicular fossa. A core biopsy was performed, leading to the diagnosis of grade 2 infiltrating ductal carcinoma, clinical stage T2N3M0 with estrogen and progesterone receptor negativity and human epidermal growth factor receptor-2 positivity. After neoadjuvant therapy, the tumor in her left breast reduced in size, but the lymph nodes remained swollen. Mastectomy and axillary lymph node dissections were performed. In the pathological findings, epithelioid cell granuloma was observed in the lymph nodes. Based on these findings, lymph node swelling was attributed to a sarcoid-like reaction.

CLINICAL DISCUSSION

SLRs have been reported in 4-14% of cancer patients. Although there are various imaging modalities for detecting swollen lymph nodes, the differential diagnosis of cancer metastasis is often difficult.

CONCLUSION

Histological evaluation of swollen lymph nodes is required to prevent overtreatment; especially in cases where the tumor size is reduced by chemotherapy, but the lymph nodes remain swollen.

Involvement of Dendritic Cells and Th17 Cells in Induced Tertiary Lymphoid Structures in a Chronic Beryllium Disease Mouse Model

Objective

To study airway pathophysiology and the role of dendritic cells (DCs) and IL-17 receptor (IL-17R) signals in a mouse model for CBD.

Methods

Here, we present a CBD mouse model in which mice were exposed to beryllium during three weeks. We also exposed IL-17R-deficient mice and mice in which DCs were depleted.

Results

Eight weeks after the initial beryllium exposure, an inflammatory response was detected in the lungs. Mice displayed inflammation of the lower airways that included focal dense infiltrates, granuloma-like foci, and tertiary lymphoid structure (TLS) containing T cells, B cells, and germinal centers. Alveolar cell analysis showed significantly increased numbers of CD4⁺ T cells expressing IFNγ, IL-17, or both cytokines. The pathogenic role of IL-17R signals was demonstrated in IL-17R-deficient mice, which had strongly reduced lung inflammation and TLS development following beryllium exposure. In CBD mice, pulmonary DC subsets including CD103⁺ conventional DCs (cDCs), CD11b⁺ cDCs, and monocyte-derived DCs (moDCs) were also prominently increased. We used diphtheria toxin receptor-mediated targeted cell ablation to conditionally deplete DCs and found that DCs are essential for the maintenance of TLS in CBD. Furthermore, the presence of antinuclear autoantibodies in the serum of CBD mice showed that CBD had characteristics of autoimmune disease.

Conclusions

We generated a translational model of sarcoidosis driven by beryllium and show that DCs and IL-17R signals play a pathophysiological role in CBD development as well as in established CBD in vivo.

An inflammatory triangle in Sarcoidosis: PPAR-γ, immune microenvironment, and inflammation

INTRODUCTION

Sarcoidosis is an inflammatory disorder characterized by granuloma formation in several organs. Sarcoidosis patients experience higher inflammatory responses resulting in pulmonary fibrosis. Although the precise mechanisms have not been well elucidated, the relationship between the immune system activation and inflammatory status is pivotal in the pathogenesis of sarcoidosis.

AREAS COVERED

Peroxisome proliferator-activated receptor (PPAR) includes the transcription factors involved in cell metabolism, proliferation, and immune response. In the alveolar macrophages of patients with sarcoidosis, the reduced activity and a decreased level of PPAR-γ have been shown. In this study, we discuss how reducing the level of PPAR-γ could lead to increased inflammation and immune responses in patients with sarcoidosis.

EXPERT OPINION

Lack of PPAR-γ may contribute to the development of a suitable milieu for the formation of immune-associated pulmonary granuloma. Reduced levels of PPAR-γ in sarcoidosis could result from over-activation of the immune system and elevated inflammatory responses, as well. Due to the anti-inflammatory function of PPAR-γ, identifying the relation between PPAR-γ, sarcoidosis development, and inflammatory state could be essential to identify the appropriate therapeutic targets. The synthesis of PPAR-γ agonists or PPAR-γ ligands may be an effective step toward the treatment of sarcoidosis patients in the future.

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.

Lymph Vessel Proliferation on Cardiac Biopsy May Help in the Diagnosis of Cardiac Sarcoidosis

Background The diagnosis of cardiac sarcoidosis ( CS ) is challenging because endomyocardial biopsy has only a 20% to 30% sensitivity rate for diagnosis and it presents with similar clinical features of idiopathic dilated cardiomyopathy ( DCM ). Lymphatic vessel proliferation in pulmonary sarcoidosis has been previously demonstrated. In this study, we compared endomyocardial biopsy samples obtained from patients with CS and DCM to determine whether lymph vessel counts using D2-40 immunostaining can be utilized as a complementary tool to distinguish CS from DCM . Methods and Results Endomyocardial biopsy tissues were obtained from 62 patients with CS (30 patients with a diagnosis made histologically, 32 patients with a diagnosis made clinically), and hematoxylin/eosin, Masson trichrome, and D2-40 immunostaining were performed. Their results were compared with those from 53 patients with DCM. The histological CS group showed significantly increased lymphatic vessels (12.0 [4.0-40.0] versus 2.6 [1.9-3.4], P<0.0001) and more severe mosaic fibrosis ( P<0.0001) compared with the DCM group. The optimal threshold was 7.5 lymphatic vessels, and this resulted in a sensitivity of 0.67 and specificity of 0.96. The clinical CS group diagnosed according to Japanese Circulation Society 2016 criteria showed increased lymphatic vessels (4.0 [3.3-9.0] versus 2.6 [1.9-3.4], P<0.0001), more severe mosaic fibrosis ( P<0.0001), more inflammatory cell infiltration (53% versus 0%, P<0.0001), and fatty infiltration within fibroblasts (50% versus 17%, P=0.0012) compared with the DCM group. The optimal threshold of lymphatic vessels was 3.5, which resulted in a sensitivity of 0.75 and specificity of 0.68. Conclusions Lymphatic vessel counts using D2-40 immunostaining may help to distinguish clinical CS without granuloma from DCM .

Plasmacytoid dendritic cells in cutaneous sarcoidosis

While absent from normal skin, plasmacytoid dendritic cells (pDCs) infiltrate the skin in several infectious, inflammatory, and neoplastic entities. In addition to providing anti-viral resistance, pDCs link the innate and adaptive immune responses. Sarcoidosis is an idiopathic multi-system granulomatous disease characterized by epitheliod granulomas. Its underlying immunopathogenesis involves hyperactivity of cell-mediated immune system with involvement of CD4+ T-helper cells of the Th1 subtype. Recently, pDCs have been shown to contribute to other cutaneous granulomatous disorders such as granuloma annulare (GA). Here, we intend to investigate pDC occurrence and activity in cutaneous sarcoidosis. Twenty cutaneous sarcoidosis cases and a comparable group of 20 cases of GA were retrieved from our database and were immunohistochemically tested for pDC occurrence and activity using anti-BDCA-2 and anti-MxA antibodies, respectively. Fifteen cases of cutaneous lupus erythrematosus (LE) were used as a comparison group. A semi-quantitative scoring system was used. pDCs were present in all cutaneous sarcoidosis in peri-vascular and/or peri-adnexal location admixed with lymphocytes. pDC numbers in sarcoidosis were comparable to those in GA, while pDCs were significantly more abundant in LE. MxA expression was mostly patchy in cutaneous sarcoidosis and GA cases, while LE cases showed diffuse and strong MxA expression. In conclusion, we have shown that pDCs are recruited into the skin lesions of sarcoidosis and GA. Despite the diminished type I IFN production demonstrated in our study, the consistent presence of pDCs in all cutaneous sarcoidosis cases speaks in favor of some role of these cells in the pathogenesis of granulomatous disorders. (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 55-61).

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.

Considerations regarding sarcoidosis in the bariatric surgical patient

The sarcoidosis patient who seeks surgical management for obesity presents many challenges. The interaction between sarcoidosis and obesity complicates both disorders and creates special issues to consider when contemplating surgery. This manuscript will review the approach to pre- and postoperative management of the sarcoidosis patient undergoing bariatric surgery.

Dendritic Cell Trafficking and Function in Rare Lung Diseases

Dendritic cells (DCs) are highly specialized immune cells that capture antigens and then migrate to lymphoid tissue and present antigen to T cells. This critical function of DCs is well defined, and recent studies further demonstrate that DCs are also key regulators of several innate immune responses. Studies focused on the roles of DCs in the pathogenesis of common lung diseases, such as asthma, infection, and cancer, have traditionally driven our mechanistic understanding of pulmonary DC biology. The emerging development of novel DC reagents, techniques, and genetically modified animal models has provided abundant data revealing distinct populations of DCs in the lung, and allow us to examine mechanisms of DC development, migration, and function in pulmonary disease with unprecedented detail. This enhanced understanding of DCs permits the examination of the potential role of DCs in diseases with known or suspected immunological underpinnings. Recent advances in the study of rare lung diseases, including pulmonary Langerhans cell histiocytosis, sarcoidosis, hypersensitivity pneumonitis, and pulmonary fibrosis, reveal expanding potential pathogenic roles for DCs. Here, we provide a review of DC development, trafficking, and effector functions in the lung, and discuss how alterations in these DC pathways contribute to the pathogenesis of rare lung diseases.

Human Lung Mononuclear Phagocytes in Health and Disease

The lungs are vulnerable to attack by respiratory insults such as toxins, allergens, and pathogens, given their continuous exposure to the air we breathe. Our immune system has evolved to provide protection against an array of potential threats without causing collateral damage to the lung tissue. In order to swiftly detect invading pathogens, monocytes, macrophages, and dendritic cells (DCs)-together termed mononuclear phagocytes (MNPs)-line the respiratory tract with the key task of surveying the lung microenvironment in order to discriminate between harmless and harmful antigens and initiate immune responses when necessary. Each cell type excels at specific tasks: monocytes produce large amounts of cytokines, macrophages are highly phagocytic, whereas DCs excel at activating naïve T cells. Extensive studies in murine models have established a division of labor between the different populations of MNPs at steady state and during infection or inflammation. However, a translation of important findings in mice is only beginning to be explored in humans, given the challenge of working with rare cells in inaccessible human tissues. Important progress has been made in recent years on the phenotype and function of human lung MNPs. In addition to a substantial population of alveolar macrophages, three subsets of DCs have been identified in the human airways at steady state. More recently, monocyte-derived cells have also been described in healthy human lungs. Depending on the source of samples, such as lung tissue resections or bronchoalveolar lavage, the specific subsets of MNPs recovered may differ. This review provides an update on existing studies investigating human respiratory MNP populations during health and disease. Often, inflammatory MNPs are found to accumulate in the lungs of patients with pulmonary conditions. In respiratory infections or inflammatory diseases, this may contribute to disease severity, but in cancer patients this may improve clinical outcomes. By expanding on this knowledge, specific lung MNPs may be targeted or modulated in order to attain favorable responses that can improve preventive or treatment strategies against respiratory infections, lung cancer, or lung inflammatory diseases.

Myocardial Immunocompetent Cells and Macrophage Phenotypes as Histopathological Surrogates for Diagnosis of Cardiac Sarcoidosis in Japanese

BACKGROUND

The histological diagnosis of cardiac sarcoidosis (CS) is based on the presence of myocardial granulomas; however, the sensitivity of endomyocardial biopsy is relatively low. We investigated whether immunocompetent cells including dendritic cells (DC) and macrophages in nongranuloma sections of endomyocardial biopsy samples could be histopathological surrogates for CS diagnosis.

METHODS AND RESULTS

The numbers of DC and macrophages were investigated in 95 consecutive CS patients and 50 patients with nonischemic cardiomyopathy as controls. All patients underwent endomyocardial biopsy, and immunohistochemical staining was performed on all samples. We examined these immunocompetent cells in nongranuloma sections in CS patients diagnosed by the presence of myocardial granulomas (n=26) and in CS patients without myocardial granulomas diagnosed by the Japanese Ministry of Health Welfare 2007 criteria (n=65) or the Heart Rhythm Society 2014 criteria (n=26). In CS patients with and without myocardial granulomas, CD209+ DC and CD68+ macrophages were more frequently observed (P<0.01) and CD163+M2 macrophages were less frequently observed (P<0.01) in nongranuloma sections compared to controls. Furthermore, the combination of decreased CD163+M2/CD68+ macrophage ratio and increased number of CD209+ DC in nongranuloma sections of CS patients demonstrated high specificity (100%, 95% CI 92.7-100) for CS diagnosis with each diagnostic criteria and the presence of myocardial granulomas.

CONCLUSIONS

Increased number of DC and decreased M2 among all macrophages in nongranuloma sections of myocardium showed high specificity for CS diagnosis, suggesting DC and macrophage phenotypes as histopathological surrogates for the diagnosis of CS.

Tissue-resident dendritic cells and diseases involving dendritic cell malfunction

Dendritic cells (DCs) control immune responses and are central to the development of immune memory and tolerance. DCs initiate and orchestrate immune responses in a manner that depends on signals they receive from microbes and cellular environment. Although DCs consist mainly of bone marrow-derived and resident populations, a third tissue-derived population resides the spleen and lymph nodes (LNs), different subsets of tissue-derived DCs have been identified in the blood, spleen, lymph nodes, skin, lung, liver, gut and kidney to maintain the tolerance and control immune responses. Tissue-resident DCs express different receptors for microbe-associated molecular patterns (MAMPs) and damage-associated molecular patterns (DAMPs), which were activated to promote the production of pro- or anti-inflammatory cytokines. Malfunction of DCs contributes to diseases such as autoimmunity, allergy, and cancer. It is therefore important to update the knowledge about resident DC subsets and diseases associated with DC malfunction.

How are cancer and connective tissue diseases related to sarcoidosis?

PURPOSE OF REVIEW

Several studies have suggested an association between sarcoidosis and cancer, and between sarcoidosis and connective tissue diseases (CTDs). In this review, we discuss the evidence supporting and refuting these associations.

RECENT FINDINGS

In terms of a cancer risk in sarcoidosis patients, the data are somewhat conflicting but generally show a very small increased risk. The data supporting an association between sarcoidosis and CTD are not as robust as for cancer. However, it appears that scleroderma is the CTD most strongly associated with sarcoidosis.

SUMMARY

There are several important clinical and research-related implications of the association of sarcoidosis and CTDs. First, rigorous efforts should be made to exclude alternative causes for granulomatous inflammation before establishing a diagnosis of sarcoidosis. Second, the association between sarcoidosis and both cancer and CTDs may yield important insights into the immunopathogenesis of all three diseases. Finally, these data provide insight in answering a common question asked by sarcoidosis patients, 'Am I at an increased risk of developing cancer?' We believe that although there is an increased (relative) risk of cancer in sarcoidosis patients compared with the general population, that increased risk is quite small (low absolute risk).

Age-related and historical changes in the clinical characteristics of sarcoidosis in Japan

BACKGROUND

National surveys conducted in Japan between 1960 and 2004 suggest a gradually increasing incidence of sarcoidosis in women >50 years old with increased involvement of the eye, skin, and heart. However, whether this involvement is due to the increased age at diagnosis is still unclear. We aimed here to identify the age-related differences in organ involvement in sarcoidosis in Japan, as well as the historical changes in clinical characteristics and the age-specific distribution of cases at diagnosis.

METHODS

We reviewed 588 consecutive Japanese patients newly diagnosed with sarcoidosis between 1974 and 2012 at Jichi Medical University Hospital. We compared organ involvement between subgroups differentiated by sex and age (<45 years; n = 275; ≥45 years; n = 313) at diagnosis and identified historical changes in the age-specific distribution in 10-year intervals.

RESULTS

Younger patients had more common involvement of extrathoracic lymph nodes, parotid/salivary gland, and liver, while older patients had more common involvement of non-lymphatic extrathoracic organs such as the eye, heart, muscle, and kidney. The age at diagnosis has consistently increased over the past four decades. The monophasic distribution in men has tended to become biphasic, and the biphasic distribution in women monophasic. Increasing trends were apparent for hypercalcemia and involvement of the gastrointestinal tract, skin, nervous system, muscle, and kidney.

CONCLUSIONS

Elderly patients at diagnosis had various extrathoracic involvement including eye, skin, and cardiac lesions. Moreover, the age at diagnosis of sarcoidosis has continued to increase in both sexes, influencing the recent trends in clinical characteristics.

Granuloma formation in pulmonary sarcoidosis

Sarcoidosis is a granulomatous disorder of unknown cause, affecting multiple organs, but mainly the lungs. The exact order of immunological events remains obscure. Reviewing current literature, combined with careful clinical observations, we propose a model for granuloma formation in pulmonary sarcoidosis. A tight collaboration between macrophages, dendritic cells, and lymphocyte subsets, initiates the first steps toward granuloma formation, orchestrated by cytokines and chemokines. In a substantial part of pulmonary sarcoidosis patients, granuloma formation becomes an on-going process, leading to debilitating disease, and sometimes death. The immunological response, determining granuloma sustainment is not well understood. An impaired immunosuppressive function of regulatory T cells has been suggested to contribute to the exaggerated response. Interestingly, therapeutical agents commonly used in sarcoidosis, such as glucocorticosteroids and anti-TNF agents, interfere with granuloma integrity and restore the immune homeostasis in autoimmune disorders. Increasing insight into their mechanisms of action may contribute to the search for new therapeutical targets in pulmonary sarcoidosis.

Immunopathogenesis of sarcoidosis and risk of malignancy: a lost truth?

The hypothesis of a relationship between sarcoidosis and malignancy was firstly formulated in 1972 by Brincker. He documented an association of sarcoid reactions or sarcoidosis with 19 lymphomas and associated malignancies. Based on various epidemiological studies, for more than 20 years sarcoidosis has been considered as a condition at increased risk for cancer, particularly lymphoproliferative disorders. The existence of a sarcoidosis-lymphoma syndrome was therefore proposed, highlighting, as a potential mechanism, the uncontrolled lymphocyte proliferation and mitotic activity. A reduced ability to eliminate an antigen and chronic inflammation have been suggested as triggering events. Leading to a reduced tumor immune surveillance, a diminished myeloid dendritic cells (mDC) function, despite up-regulated co-stimulatory and maturation markers, was also raised as potential mechanism. However, some subsequent studies have questioned the presence of a close association between the two entities and have explained those previously published as the result of selection bias and misclassification. Recently, a Swedish population-based cohort study documented a significant overall excess incidence of cancer among sarcoidosis patients, especially those with multiple hospitalizations or admission in older age, emphasizing again a potential neoplastic risk. Therefore, currently, whether these patients have an increased risk of developing malignant lesions is still debated. Larger and unbiased studies are needed before drawing definite conclusions.

Sarcoidosis: Immunopathogenesis and Immunological Markers

Sarcoidosis is a multisystem granulomatous disorder invariably affecting the lungs. It is a disease with noteworthy variations in clinical manifestation and disease outcome and has been described as an “immune paradox” with peripheral anergy despite exaggerated inflammation at disease sites. Despite extensive research, sarcoidosis remains a disease with undetermined aetiology. Current evidence supports the notion that the immune response in sarcoidosis is driven by a putative antigen in a genetically susceptible individual. Unfortunately, there currently exists no reliable biomarker to delineate the disease severity and prognosis. As such, the diagnosis of sarcoidosis remains a vexing clinical challenge. In this review, we outline the immunological features of sarcoidosis, discuss the evidence for and against various candidate etiological agents (infective and noninfective), describe the exhaled breath condensate, a novel method of identifying immunological biomarkers, and suggest other possible immunological biomarkers to better characterise the immunopathogenesis of sarcoidosis.

Sarcoidosis: a comprehensive review and update for the dermatologist: part I. Cutaneous disease

Sarcoidosis is a common systemic, noncaseating granulomatous disease of unknown etiology. The development of sarcoidosis has been associated with a number of environmental factors and genes. Cutaneous sarcoidosis, the "great imitator," can baffle clinicians because of its diverse manifestations and its ability to resemble both common and rare cutaneous diseases. Depending on the type, location, and distribution of the lesions, treatment can prevent functional impairment, symptomatic distress, scarring, and disfigurement. Numerous therapeutic options are available for the treatment of cutaneous sarcoidosis, but there are few well designed trials to guide practitioners on evidence-based, best practice management. In part I, we review the current knowledge and advances in the epidemiology, etiology, pathogenesis, and genetics of sarcoidosis, discuss the heterogeneous manifestations of cutaneous sarcoidosis, and provide a guide for treatment of cutaneous sarcoidosis.

Evidence for local dendritic cell activation in pulmonary sarcoidosis

Background

Sarcoidosis is a granulomatous disease characterized by a seemingly exaggerated immune response against a difficult to discern antigen. Dendritic cells (DCs) are pivotal antigen presenting cells thought to play an important role in the pathogenesis. Paradoxically, decreased DC immune reactivity was reported in blood samples from pulmonary sarcoidosis patients. However, functional data on lung DCs in sarcoidosis are lacking. We hypothesized that at the site of disease DCs are mature, immunocompetent and involved in granuloma formation.

Methods

We analyzed myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) in broncho-alveolar lavage (BAL) and blood from newly diagnosed, untreated pulmonary sarcoidosis patients and healthy controls using 9-color flowcytometry. DCs, isolated from BAL using flowcytometric sorting (mDCs) or cultured from monocytes (mo-DCs), were functionally assessed in a mixed leukocyte reaction with naïve allogeneic CD4+ T cells. Using Immunohistochemistry, location and activation status of CD11c⁺DCs was assessed in mucosal airway biopsies.

Results

mDCs in BAL, but not in blood, from sarcoidosis patients were increased in number when compared with mDCs from healthy controls. mDCs purified from BAL of sarcoidosis patients induced T cell proliferation and differentiation and did not show diminished immune reactivity. Mo-DCs from patients induced increased TNFα release in co-cultures with naïve allogeneic CD4⁺ T cells. Finally, immunohistochemical analyses revealed increased numbers of mature CD86⁺ DCs in granuloma-containing airway mucosal biopsies from sarcoidosis patients.

Conclusion

Taken together, these finding implicate increased local DC activation in granuloma formation or maintenance in pulmonary sarcoidosis.

Increased IL-17A expression in granulomas and in circulating memory T cells in sarcoidosis

OBJECTIVE

Sarcoidosis is a systemic inflammatory disorder characterized by granulomas. Although the aetiology is unknown, sarcoidosis is thought to be mediated by Th1 lymphocytes. Recently, IL-17A has been implicated in granuloma formation in various diseases, including tuberculosis. Therefore, we hypothesized that Th17 cells play a role in sarcoidosis, paralleling recent findings in autoimmune diseases such as RA. The aim of our study was to investigate the role of Th17 cells in sarcoidosis.

METHODS

T cells were investigated by intracellular flow cytometry and immunohistochemistry, in blood, bronchoalveolar lavages (BALs) and bronchial mucosal biopsies from a cohort of newly diagnosed sarcoidosis patients and healthy controls.

RESULTS

Circulating memory CD4(+) T-cell populations of sarcoidosis patients contained significantly increased proportions of IL-17A(+) cells when compared with healthy controls. Interestingly, proportions of IL-17A/IFN-γ and IL-17A/IL-4 double-producing cells were significantly increased in blood of sarcoidosis patients and were present in substantial numbers in BAL. In granuloma-containing, but not in non-granulomatous sarcoidosis biopsies, we found significantly increased numbers of IL-17A(+) T cells, located in and around granulomas throughout the lamina propria. IL-22(+) T cells were increased in the subepithelial layer.

CONCLUSIONS

Enhanced IL-17A expression in granulomas and the presence of IL-17A(+), IL-17A(+)IFN-γ(+) and IL-17A(+)IL-4(+)memory Th cells in the circulation and BAL indicate Th17 cell involvement in granuloma induction or maintenance in sarcoidosis. Therefore, neutralization of IL-17A activity may be a novel strategy to treat sarcoidosis.

Molecular profiling and gene expression analysis in cutaneous sarcoidosis: the role of interleukin-12, interleukin-23, and the T-helper 17 pathway

BACKGROUND

Cutaneous sarcoidosis (CS) skin provides relatively noninvasive access to granulomatous sarcoidosis tissue.

OBJECTIVE

We sought to explore the role of the T-helper (Th)1 and Th17 pathways in sarcoidosis.

METHODS

We used molecular profiling and gene expression analysis to analyze the Th1 and Th17 pathways and other immune-mediated pathways in CS. Molecular profiles were obtained from sarcoidosis skin lesions (lesional skin [LS]), unaffected skin from patients with CS (non-LS), and the skin of healthy control subjects. Whole blood was collected to compare the molecular profile of sarcoidosis skin lesions and whole blood.

RESULTS

Twenty participants were enrolled: 15 with active CS and 5 healthy volunteers. Microarray analyses comparing non-LS and healthy volunteer skin with LS showed several thousand genes differentially expressed (≥2-fold change false discovery rate, P < .01). Targeted selections of genes associated with Th1 and Th17 phenotypes showed a strong Th1 profile of sarcoidosis and expression of interleukin (IL)-23 and IL-23R with limited expression of other Th17 pathway genes. IL-21 and signal transducer and activator of transcription 3 (STAT3) were also dysregulated in skin and whole blood, providing additional evidence for involvement of the IL-12 pathway and potential activation of the Th17 pathway.

LIMITATIONS

Measurements were made at a single point in time and may not identify mechanisms that may be identified in patients followed up longitudinally.

CONCLUSION

These findings provide novel insight into the dysregulated pathways that may be involved in the pathogenesis of sarcoidosis.

Sarcoidal reactions in regional lymph nodes of patients with early stage non-small cell lung cancer predict improved disease-free survival: a pilot case-control study

Sarcoidal reactions occurring in regional lymph nodes of patients with non-small cell lung carcinoma appear to be limited to patients with stage I disease. The prognostic significance of this remains unknown. Such reactions are thought to represent a cell-mediated antitumor response and have been associated with improved outcomes in other solid organ malignancies. We performed a retrospective chart review of all patients undergoing lobectomy with curative intent for non-small cell lung carcinoma. Eligible cases were selected based on pathologic reports, with matched controls then drawn from the same surgical cohort. One hundred fifty-seven patients underwent lobectomy and lymph node dissection. Eight patients with sarcoidal granulomas present in regional lymph nodes were identified as cases and matched to 16 control subjects. All subjects were staged pN0. Disease recurrence was noted in no case subjects but in 7 (44%) of control subjects (P = .044, χ(2) = 4.051). The presence of sarcoidal reactions within regional lymph nodes of patients with non-small cell lung carcinoma predicts a lower rate of disease recurrence after definitive surgical resection. The exact mechanism by which antitumor immunity is achieved remains to be elucidated.

Adaptive immune responses in primary cutaneous sarcoidosis

Sarcoidosis is a multisystemic inflammatory disorder with cutaneous lesions present in about one-quarter of the patients. Cutaneous lesions have been classified as specific and nonspecific, depending on the presence of nonnecrotizing epithelial cell granulomas on histologic studies. The development and progression of specific cutaneous sarcoidosis involves a complex interaction between cells of the adaptive immune systems, notably T-lymphocytes and dendritic cells. In this paper, we will discuss the role of T-cells and skin dendritic cells in the development of primary cutaneous sarcoidosis and comment on the potential antigenic stimuli that may account for the development of the immunological response. We will further explore the contributions of selected cytokines to the immunopathological process. The knowledge of the adaptive immunological mechanisms operative in cutaneous sarcoidosis may subsequently be useful for identifying prevention and treatment strategies of systemic sarcoidosis.

Hepatic granulomas: pathogenesis and differential diagnosis

Granulomatous liver disease constitutes a category of hepatic disorders and is at present diagnosed in approximately 4% of liver biopsies. Hepatic granulomas develop through the interactions of T lymphocytes and macrophages, with the integral involvement of T-helper (T(H)) 1 or T(H)2 pathways or both, depending on the specific granulomatous disease. Hepatic granulomas may be manifested clinically by elevated levels of serum alkaline phosphatase and g-glutamyltransferase enzymes, damage to specific structures (eg, intrahepatic bile ducts in primary biliary cirrhosis), or infrequently, progressive liver disease with portal hypertension and cirrhosis (eg, sarcoidosis). Systemic immunologic disorders, infectious diseases, drug hepatotoxicity, and reaction to neoplastic disease are the major causative factors responsible for granulomas in the liver. These causes and recent epidemiologic trends are covered in this discussion.