Selective activation and accumulation of oligoclonal V beta-specific T cells in active pulmonary sarcoidosis

T-Cell Receptor Sequences Identify Combined Coxsackievirus-Streptococci Infections as Triggers for Autoimmune Myocarditis and Coxsackievirus-Clostridia Infections for Type 1 Diabetes

Recent research suggests that T-cell receptor (TCR) sequences expanded during human immunodeficiency virus and SARS-CoV-2 infections unexpectedly mimic these viruses. The hypothesis tested here is that TCR sequences expanded in patients with type 1 diabetes mellitus (T1DM) and autoimmune myocarditis (AM) mimic the infectious triggers of these diseases. Indeed, TCR sequences mimicking coxsackieviruses, which are implicated as triggers of both diseases, are statistically significantly increased in both T1DM and AM patients. However, TCRs mimicking Clostridia antigens are significantly expanded in T1DM, whereas TCRs mimicking Streptococcal antigens are expanded in AM. Notably, Clostridia antigens mimic T1DM autoantigens, such as insulin and glutamic acid decarboxylase, whereas Streptococcal antigens mimic cardiac autoantigens, such as myosin and laminins. Thus, T1DM may be triggered by combined infections of coxsackieviruses with Clostridia bacteria, while AM may be triggered by coxsackieviruses with Streptococci. These TCR results are consistent with both epidemiological and clinical data and recent experimental studies of cross-reactivities of coxsackievirus, Clostridial, and Streptococcal antibodies with T1DM and AM antigens. These data provide the basis for developing novel animal models of AM and T1DM and may provide a generalizable method for revealing the etiologies of other autoimmune diseases. Theories to explain these results are explored.

Recurrence of primary disease following lung transplantation

Lung transplant has become definitive treatment for patients with several end-stage lung diseases. Since the first attempted lung transplantation in 1963, survival has significantly improved due to advancement in immunosuppression, organ procurement, ex vivo lung perfusion, surgical techniques, prevention of chronic lung allograft dysfunction and bridging to transplant using extracorporeal membrane oxygenation. Despite a steady increase in number of lung transplantations each year, there is still a huge gap between demand and supply of organs available, and work continues to select recipients with potential for best outcomes. According to review of the literature, there are some rare primary diseases that may recur following transplantation. As the number of lung transplants increase, we continue to identify disease processes at highest risk for recurrence, thus shaping our future approaches. While the aim of lung transplantation is improving survival and quality of life, choosing the best recipients is crucial due to a shortage of donated organs. Here we discuss the common disease processes that recur and highlight its impact on overall outcome following lung transplantation.

This article reviews the underlying conditions leading to lung transplant with potential for recurrence and the impact of such recurrences on the overall outcome following transplanthttps://bit.ly/3v3gSvJ

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.

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.

Shared αβ TCR Usage in Lungs of Sarcoidosis Patients with Löfgren's Syndrome

Sarcoidosis is a granulomatous disease that primarily affects the lungs and is characterized by an accumulation of CD4⁺ T cells in the bronchoalveolar lavage (BAL). Previous work has indicated that HLA-DRB1*03:01⁺ (DR3⁺) patients diagnosed with the acute form of the disease, Löfgren's syndrome (LS), have an accumulation of CD4⁺ T cells bearing TCRs using TRAV12-1 (formerly AV2S3). However, the importance of these α-chains in disease pathogenesis and the paired TCRβ-chain remains unknown. This study aimed to identify expanded αβTCR pairs expressed on CD4⁺ T cells derived from the BAL of DR3⁺ LS patients. Using a deep-sequencing approach, we determined TCRα- and TCRβ-chain usage, as well as αβTCR pairs expressed on BAL CD4⁺ T cells from LS patients. TRAV12-1 and TRBV2 (formerly BV22) were the most expanded V region gene segments in DR3⁺ LS patients relative to control subjects, and TRAV12-1 and TRBV2 CDR3 motifs were shared among multiple DR3⁺ LS patients. When assessing αβTCR pairing, TRAV12-1 preferentially paired with TRBV2, and these TRAV12-1/TRBV2 TCRs displayed CDR3 homology. These findings suggest that public CD4⁺ TCR repertoires exist among LS patients and that these T cells are recognizing the putative sarcoidosis-associated Ag(s) in the context of DR3.

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.

Autoimmunity and the microbiome: T-cell receptor mimicry of "self" and microbial antigens mediates self tolerance in holobionts: The concepts of "holoimmunity" (TcR-mediated tolerance for the holobiont) and "holoautoimmunity" (loss of tolerance for the holobiont) are introduced

I propose a T-cell receptor (TcR)-based mechanism by which immunity mediates both "genetic self" and "microbial self" thereby, connecting microbiome disease with autoimmunity. The hypothesis is based on simple principles. First, TcR are selected to avoid strong cross-reactivity with "self," resulting in selection for a TcR repertoire mimicking "genetic self." Second, evolution has selected for a "microbial self" that mimics "genetic self" so as to share tolerance. In consequence, our TcR repertoire also mimics microbiome antigenicity, providing a novel mechanism for modulating tolerance to it. Also, the microbiome mimics the TcR repertoire, acting as a secondary immune system. I call this TcR-microbiome mimicry "holoimmunity" to denote immune tolerance to the "holobiont self." Logically, microbiome-host mimicry means that autoimmunity directed at host antigens will also attack components of the microbiome, and conversely, an immunological attack on the microbiome may cross-react with host antigens producing "holoautoimmunity."

Immunogenetics of Disease-Causing Inflammation in Sarcoidosis

Sarcoidosis is a systemic inflammatory disorder characterised by tissue infiltration by mononuclear phagocytes and lymphocytes with associated non-caseating granuloma formation. Originally described as a disorder of the skin, sarcoidosis can involve any organ with wide-ranging clinical manifestations and disease course. Recent studies have provided new insights into the mechanisms involved in disease pathobiology, and we now know that sarcoidosis has a clear genetic basis largely involving human leukocyte antigen (HLA) genes. In contrast to Mendelian-monogenic disorders--which are generally due to specific and relatively rare mutations often leading to a single amino acid change in an encoded protein--sarcoidosis results from genetic variations relatively common in the general population and involving multiple genes, each contributing an effect of varying magnitude. However, an individual may have the necessary genetic profile and yet the disease will not develop unless an environmental or infectious factor is encountered. Genetics appears also to contribute to the huge variability in clinical phenotype and disease behaviour. Moreover, it has been established that sarcoidosis granulomatous inflammation is a highly polarized T helper 1 immune response that starts with an antigenic stimulus followed by T cell activation via a classic HLA class II-mediated pathway. A complex network of lymphocytes, macrophages, and cytokines is pivotal in the orchestration and evolution of the granulomatous process. Despite these advances, the aetiology of sarcoidosis remains elusive and its pathogenesis incompletely understood. As such, there is an urgent need for a better understanding of disease pathogenesis, which hopefully will translate into the development of truly effective therapies.

T-cell receptor–HLA-DRB1 associations suggest specific antigens in pulmonary sarcoidosis

In pulmonary sarcoidosis, CD4+ T-cells expressing T-cell receptor Vα2.3 accumulate in the lungs of HLA-DRB1*03+ patients. To investigate T-cell receptor-HLA-DRB1*03 interactions underlying recognition of hitherto unknown antigens, we performed detailed analyses of T-cell receptor expression on bronchoalveolar lavage fluid CD4+ T-cells from sarcoidosis patients.

Pulmonary sarcoidosis patients (n=43) underwent bronchoscopy with bronchoalveolar lavage. T-cell receptor α and β chains of CD4+ T-cells were analysed by flow cytometry, DNA-sequenced, and three-dimensional molecular models of T-cell receptor-HLA-DRB1*03 complexes generated.

Simultaneous expression of Vα2.3 with the Vβ22 chain was identified in the lungs of all HLA-DRB1*03+ patients. Accumulated Vα2.3/Vβ22-expressing T-cells were highly clonal, with identical or near-identical Vα2.3 chain sequences and inter-patient similarities in Vβ22 chain amino acid distribution. Molecular modelling revealed specific T-cell receptor-HLA-DRB1*03-peptide interactions, with a previously identified, sarcoidosis-associated vimentin peptide, (Vim)429–443 DSLPLVDTHSKRTLL, matching both the HLA peptide-binding cleft and distinct T-cell receptor features perfectly.

We demonstrate, for the first time, the accumulation of large clonal populations of specific Vα2.3/Vβ22 T-cell receptor-expressing CD4+ T-cells in the lungs of HLA-DRB1*03+ sarcoidosis patients. Several distinct contact points between Vα2.3/Vβ22 receptors and HLA-DRB1*03 molecules suggest presentation of prototypic vimentin-derived peptides.

Sarcoidosis mimicking lymphoma on FDG-PET imaging

Sarcoidosis is an inflammatory, systemic disease characterized by noncaseating granulomas. We describe a case of a 52-year-old female who presented with fevers, chills, night sweats, and weight loss of four months' duration. Lymphoma was suspected, and results of advanced imaging procedures were also consistent with lymphoma. However, mediastinal lymph-node biopsy, bone-marrow aspiration, and biopsy revealed noncaseating granulomas. She was diagnosed with sarcoidosis and had a positive therapeutic response to drug therapy. This case study illustrates that sarcoidosis can be a pitfall in 18-F-fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging, which may lead to false-positive diagnosis of malignancy. PET-positive lesions do not always indicate malignancy, and histological confirmation of the lesions with biopsy should always be performed.

T cell receptor-Vβ repertoires in lung and blood CD4+ and CD8+ T cells of pulmonary sarcoidosis patients

Background

Sarcoidosis patients have accumulations of activated CD4⁺ T cells in affected organs, such as the lungs. T cell receptor (TCR) Vβ-chain usage has been incompletely characterized in these patients.

Methods

We surveyed the TCR Vβ usage in CD4⁺ and CD8⁺ T cells in bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear cells (PBMC) from 15 HLA-typed Scandinavian sarcoidosis patients. In addition, PBMC from 9 healthy volunteers and BAL cells from three of them were examined. Using 21 Vβ family-specific antibodies, we covered approximately 70% of all Vβ chains.

Results

In BAL T cells from sarcoidosis patients, we identified 16 CD4⁺ T cell expansions in 271 analyses (5.9%) and 21 CD8⁺ expansions in 240 analyses (8.7%). In PBMC we found 9 CD4⁺ expansions in 276 analyses (3.3%) and 12 CD8⁺ expansions out of 263 analyses (4.6%). Consistent with previous studies we found Vβ8 and Vβ16 expansions in sarcoidosis patients’ lungs. In addition, we found lung restricted Vβ22 expansions in three HLA DRB1 03⁺ patients. However, we found no statistically significant difference in frequency of expansions between patients and healthy controls.

Conclusions

The identified T cell expansions in present study indicate specific antigen recognition in the lungs of sarcoidosis patients.

[Role of T lymphocyte cyclic nucleotides and G protein in sarcoidosis]

CD4+ T lymphocytes play a major role in the pathophysiology of sarcoidosis. Many studies have investigated the immunological and genetic abnormalities in this disease. There are few studies concerning the metabolic pathways. Essentially they concern the pathways: STAT1, MAPK38, NF-κB, Galphai, cAMP and cGMP PDE and PEMT1. Using studies in the literature and results of our own work concerning some metabolic aspects of T lymphocytes in sarcoidosis, we present a revue of the various hypotheses, which involve dysfunction of cAMP signaling pathways, such as RAS/RAF/MEK/ERK in T lymphocytes, leading to a disorder of immunity.

HLA associations and Löfgren's syndrome

Patients with sarcoidosis can be subgrouped according to organ engagement and clinical manifestations. One such subgroup is Löfgren's syndrome (LS), constituting a distinct group of sarcoidosis patients with typical clinical manifestations, separate genetic associations and an immune response that seems to differ from that of non-LS patients. In particular, LS patients have strong associations with HLA-DRB1 alleles, and the well-known association with HLA-DRB1*03 is particularly striking. This particular HLA-DRB1 allele is also a very strong marker within that particular group of patients for a prognostically favorable disease course. This article will mainly discuss genetic associations with LS, and the possible implications of such associations.

Etiology of sarcoidosis: does infection play a role?

Sarcoidosis is a granulomatous inflammatory disorder of unclear etiology, which is known to affect multiple organ systems including the lungs, heart, skin, central nervous system, and eyes, among others. For this reason, sarcoidosis represents a systemic medical disorder that is clinically relevant to multiple medical sub-specialties. Despite extensive research, the etiology of sarcoidosis has yet to be elucidated, although most evidence supports that the pathogenetic mechanism of sarcoidosis is an aberrant immune response, driven by an unidentified antigen (or antigens) in genetically susceptible individuals. Multiple candidate etiologic agents, including microbial organisms and environmental agents, have been investigated, but study results are inconclusive. In this review, we describe the known histologic and immunologic features of sarcoidosis and discuss the evidence supporting a role for infectious processes in the pathogenesis of sarcoidosis.

Evidence for mycobacteria in sarcoidosis

Despite its recognition as a distinct granulomatous disease for over a century, the etiology of sarcoidosis remains to be defined. Since the early 1900s, infectious agents have been suspected in causing sarcoidosis. For much of this time, mycobacteria were considered a likely culprit, yet until recently, the supporting evidence has been tenuous at best. In this review, we evaluate the reported association between mycobacteria and sarcoidosis. Historically, mycobacterial infection has been investigated using histologic stains, cultures of lesional tissue or blood, and identification of bacterial nucleic acids or bacterial antigens. More recently, advances in biochemical, molecular, and immunological methods have produced a more rigorous analysis of the antigenic drivers of sarcoidosis. The result of these efforts indicates that mycobacterial products likely play a role in at least a subset of sarcoidosis cases. This information, coupled with a better understanding of genetic susceptibility to this complex disease, has therapeutic implications.

[Sarcoidosis and genetics]

Familial features of sarcoidosis and observations in monozygotic twins affected by the condition suggest the presence of a genetic predisposition. Various genetic associations have been described with genes coding for proteins involved in immune regulation in particular at the level of interaction between T-lymphocyte and antigen presenting cell. We review the various genetic targets described with techniques ranging from classic human lymphocyte antigen genotype to genome wide linkage scans. The 6p21 region has been highlighted, which includes relevant genes such as MHC class II, BTNL2 and TNFα. These studies show that the genetics of sarcoidosis are complex, that patient sub-groups exist, which may explain some of the heterogeneity in the results of genetic studies and that the interactions between genetic and environmental factors remains to be elucidated.

CD4+ T cells in sarcoidosis: targets and tools

Activated pulmonary T-helper type 1 lymphocytes are essential for the inflammatory process in sarcoidosis. Both the T cells and their mediators promoting inflammation may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor AV2S3(+) CD4(+) T cells, are found at dramatically increased levels in the bronchoalveolar lavage fluid of a subpopulation of sarcoidosis patients with active disease. This particular T-cell subset may be used as a tool to reveal a sarcoidosis-specific antigen. Recent studies of natural killer T cells and T regulatory cells from patients with sarcoidosis have described abnormalities that may be relevant for the inflammatory process in this disease. These findings are exciting news and may be of help for designing new treatment strategies.

Dendritic cells in the pathogenesis of sarcoidosis

Sarcoidosis is a noncaseating granulomatous disease, likely of autoimmune etiology, that causes inflammation and tissue damage in multiple organs, most commonly the lung, but also skin, and lymph nodes. Reduced dendritic cell (DC) function in sarcoidosis peripheral blood compared with peripheral blood from control subjects suggests that blunted end organ cellular immunity may contribute to sarcoidosis pathogenesis. Successful treatment of sarcoidosis with tumor necrosis factor (TNF) inhibitors, which modulate DC maturation and migration, has also been reported. Together, these observations suggest that DCs may be important mediators of sarcoidosis immunology. This review focuses on the phenotype and function of DCs in the lung, skin, blood, and lymph node of patients with sarcoidosis. We conclude that DCs in end organs are phenotypically and functionally immature (anergic), while DCs in the lymph node are mature and polarize pathogenic Th1 T cells. The success of TNF inhibitors is thus likely secondary to inhibition of DC-mediated Th1 polarization in the lymph node.

T cell responses to mycobacterial catalase-peroxidase profile a pathogenic antigen in systemic sarcoidosis

Sarcoidosis is a systemic granulomatous disease associated with local epithelioid granulomas, CD4(+) T cells, and Th1 cytokines. The tissue Ags that drive this granulomatous inflammation are uncertain. In this study, we used IFN-gamma-ELISPOT assays and flow cytometry to assess lung and blood T cell responses to the candidate pathogenic Ag, Mycobacterium tuberculosis catalase-peroxidase (mKatG) in patients with sarcoidosis from two centers. Despite differences in patient phenotypic, genetic, and prognostic characteristics, we report that T cell responses to mKatG were remarkably similar in these cohorts, with higher frequencies of mKatG-reactive, IFN-gamma-expressing T cells in the blood of sarcoidosis patients compared with nontuberculosis sensitized healthy controls, and (in a subset) in greater numbers than T cells reactive to purified protein derivative. In sarcoidosis, mKatG-reactive CD4(+) Th1 cells preferentially accumulated in the lung, indicating a compartmentalized response. Patients with or without Löfgren syndrome had similar frequencies of mKatG specific IFN-gamma-expressing blood T cells. Circulating mKatG-reactive T cells were found in chronic active sarcoidosis but not in patients with inactive disease. Together, these results demonstrate that T cell responses to mKatG in sarcoidosis fit a profile expected for a pathogenic Ag, supporting an immunotherapeutic approach to this disease.

Role of CD4+ T cells in sarcoidosis

Activated pulmonary CD4(+) T lymphocytes of the Th-1 type are essential for the inflammatory process in sarcoidosis, and IFN-gamma production is crucial for the characteristic granuloma formation. Both the T cells and their inflammatory mediators may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor (TCR) AV2S3(+) bronchoalveolar lavage (BAL) CD4(+) T cells, is found at dramatically increased levels in the BAL fluid of human leukocyte antigen (HLA)-DRB1*0301-positive and/or HLA-DRB3*0101-positive patients with sarcoidosis. The AV2S3(+) BAL CD4(+) T cells strongly associate with the sarcoid inflammation, and future studies on this particular T-cell subset to reveal their specificity may lead to the identification of sarcoidosis-specific antigen(s). T-cell subpopulations with regulatory functions (i.e., natural killer T cells and T regulatory cells) have recently been described as abnormal in sarcoidosis. Dysfunctional regulatory T cells may allow T effector cells to contribute to the formation of granulomas, and they may thus be relevant for the inflammatory process in this disease. These findings are exciting news and will be of help in designing new treatment strategies.

The immune paradox of sarcoidosis and regulatory T cells

Sarcoidosis is characterized by extensive local inflammation (granuloma, cytokine secretion) associated with anergy (poor response to antigens in vitro and in vivo). We postulated that this paradoxical situation would correspond to a disequilibrium between effector and regulatory T lymphocytes (T reg cells). We show that CD4⁺CD25^brightFoxP3⁺ cells accumulate at the periphery of sarcoid granulomas, in bronchoalveolar lavage fluid, and in peripheral blood of patients with active disease. These cells exhibited powerful antiproliferative activity, yet did not completely inhibit TNF-α production. Sarcoidosis is therefore associated with a global T reg cell subset amplification whose activity would be insufficient to control local inflammation. At the same time, peripheral T reg cells exert powerful antiproliferative activity that may account for the state of anergy. Altogether, these findings advance our conceptual understanding of immune regulation in a way that resolves the immune paradox of sarcoidosis and permit us to envisage a profound clinical impact of T reg cell manipulation on immunity.

Mycobacterial catalase-peroxidase is a tissue antigen and target of the adaptive immune response in systemic sarcoidosis

Sarcoidosis is a disease of unknown etiology characterized by noncaseating epithelioid granulomas, oligoclonal CD4(+) T cell infiltrates, and immune complex formation. To identify pathogenic antigens relevant to immune-mediated granulomatous inflammation in sarcoidosis, we used a limited proteomics approach to detect tissue antigens that were poorly soluble in neutral detergent and resistant to protease digestion, consistent with the known biochemical properties of granuloma-inducing sarcoidosis tissue extracts. Tissue antigens with these characteristics were detected with immunoglobulin (Ig)G or F(ab')(2) fragments from the sera of sarcoidosis patients in 9 of 12 (75%) sarcoidosis tissues (150-160, 80, or 60-64 kD) but only 3 of 22 (14%) control tissues (all 62-64 kD; P = 0.0006). Matrix-assisted laser desorption/ionization time of flight mass spectrometry identified Mycobacterium tuberculosis catalase-peroxidase (mKatG) as one of these tissue antigens. Protein immunoblotting using anti-mKatG monoclonal antibodies independently confirmed the presence of mKatG in 5 of 9 (55%) sarcoidosis tissues but in none of 14 control tissues (P = 0.0037). IgG antibodies to recombinant mKatG were detected in the sera of 12 of 25 (48%) sarcoidosis patients compared with 0 of 11 (0%) purified protein derivative (PPD)(-) (P = 0.0059) and 4 of 10 (40%) PPD(+) (P = 0.7233) control subjects, suggesting that remnant mycobacterial catalase-peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis.

Clinical and immunologic components of sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown etiology that affects the lungs and the lymphatic system. It is seen by specialists in allergy, rheumatology, and pulmonary disease. Although there are no clues to etiology, an environmental basis has been implicated primarily on the basis of epidemiologic and anecdotal data. The majority of patients are very readily diagnosed and should not be confused with other pulmonary disorders. Sarcoidosis can become an issue if it occurs in the presence of other significant pulmonary disease, such as patients with asthma or hypersensitivity pneumonitis. Most patients remain asymptomatic and many are diagnosed when picked up on a routine screening exam. Steroids can be used to manage some patients but caution should be exercised to choose the appropriate dose and to treat patients for a limited period of time to avoid the complications of steroids. A minority of patients do progress to significant disease, including morbidity and mortality, and further research is needed to determine more appropriate and specific therapy for such situations.

Obstructive sarcoidosis

Sarcoidosis is a systemic granulomatous disease that frequently involves the lung. Although classically thought of as a restrictive lung disease, airway obstruction has become a recognized feature of the disease in the past years. Sarcoidosis can affect the airway at any level and when the involvement includes small airways, it can resemble more common obstructive airway diseases, such as asthma and chronic bronchitis. Pulmonary function testing and high-resolution computerized tomography of the chest are two important tools to evaluate the presence and extent of airway obstruction in sarcoidosis. Pharmacologic options for the treatment of obstructive sarcoidosis are, in large part, not supported by large, randomized clinical trials. In severe cases of bronchostenosis owing to sarcoidosis granuloma or extrinsic compression from intrathoracic lymphadenopathy, interventional bronchoscopy has successfully been performed, although repeated procedures are usually required. Lung transplantation is an ultimate option in selected patients with late-stage fibrotic disease.

Characterization of bronchoalveolar lavage T cell subsets in sarcoidosis on the basis of CD57, CD4 and CD8

T cells expressing CD57 (a natural killer cell marker) with interferon-gamma (IFN-gamma) producing capacity increase under various conditions. CD57+ T cells are also present in the bronchoalveolar lavage fluid (BALF) of sarcoidosis, and several phenotypical and functional analyses of these cells have been reported. In the present study, BALF T cells obtained from 52 patients with sarcoidosis were classified further into CD4+CD57+ T cells, CD4+CD57- T cells, CD8+CD57+ T cells and CD8+CD57- T cells and their phenotypes and functional characteristics were assessed. Substantial proportions of these T cell subsets expressed natural killer cell markers CD161 and CD122. The biased expansion of Vbeta2 T cells was observed in both CD4+CD57+ T cells and CD4+CD57- T cells in BALF from most patients, while the expansion of other Vbeta T cells was also observed in some patients. Unexpectedly, the biased expansion of certain Vbeta T cells was also seen in either CD8+CD57+ T cells or CD8+CD57- T cells, while the expanded Vbeta T cells in CD8+ T cells differed substantially among individuals. BALF T cells showed a remarkably lower T cell receptor (TCR) intensity than that of peripheral blood T cells. Both CD8+ T cell subsets in BALF of sarcoidosis expressed the intracellular perforin/granzyme B, while all four subsets expressed intracellular IFN-gamma after in vitro activation, and CD4+ T cells, especially CD4+CD57+ T cells, expressed tumour necrosis factor-alpha. These findings indicate that CD57+ T cells as well as CD57- T cells in the BALF are phenotypically and functionally different from peripheral blood T cells and may play an important role in the Th1 dominant state and inflammation in pulmonary sarcoidosis.

Treatment of sarcoidosis -- from a basic science point of view

Progress in our understanding of the scientific basis of granulomatous inflammation in sarcoidosis provides a framework for enlightened treatment decisions. Current evidence supports the concept that the pathogenesis of sarcoidosis involves a highly polarized T-helper 1 (Th1) immune response to pathogenic tissue antigens. Conventional treatment is focused on attenuating granuloma formation with antimalarial drugs that inhibit antigen presentation or with nonspecific anti-inflammatory agents such as glucocorticosteroids, methotrexate, or azathioprine. Anti-tumour necrosis factor (TNF)-alpha agents such as pentoxifylline, thalidomide, etanercept and remicade, have recently shown some successes in sarcoidosis. Designing future therapies depends on improved knowledge of the critical immunological processes operative in different stages of disease.

Nonpulmonary manifestations of sarcoidosis

Sarcoidosis is one in a heterogeneous family of granulomatous disorders. The clinical manifestations of sarcoidosis can vary widely, depending on the patient and the tissues involved. Recent advances in our understanding of the immunologic steps leading to granuloma formation and persistence have yet to translate into more effective care for patients with this disease. This review discusses the immunology of granuloma formation and systemic disease, the various nonpulmonary expressions of the clinical disease, and the treatment options available to the practicing physician.

Specific bronchoalveolar lavage fluid T cells associate with disease in a pair of monozygotic twins discordant for sarcoidosis

A 49-year-old Caucasian woman had an acute onset of sarcoidosis. Bronchoscopy with bronchoalveolar lavage (BAL) showed a pronounced accumulation of BAL fluid CD4+ T cells expressing the T-cell receptor (TCR) AV2S 3 gene. In line with this observation, the patient was HLA-DR 17 positive, previously shown to strongly correlate with lung compartmentalized AV2S3+ T cells. At follow-up after recovery, reduced numbers of BAL fluid AV2S3+ T cells were found. Interestingly, BAL fluid of a healthy monozygotic twin sister contained normal numbers of AV2S3+ lung T cells. This report shows the T-cell repertoire of BAL fluid T cells to correlate with the disease (sarcoidosis). indicating a local and specific immune response triggered by an unknown antigen in sarcoidosis.

Alveolar macrophage-T cell interactions during Th1-type sarcoid inflammation

Sarcoidosis is an immunomediated, multisystem disorder of unknown cause(s) characterized by a heightened Th1 immune response that leads to an uncontrolled granuloma formation at sites of disease activity. The past few years have seen outstanding advances in the understanding of immunological and molecular events involved in the pathogenesis of this disease. The idea is that several cytokines and chemokines, which are secreted at sites of disease activity, participate in granuloma formation. This paper describes recent data that have clarified some of the events that govern the development of the hypersensitivity reaction during sarcoidosis. In particular, we will review recent evidence indicating that a complex relationship exists between the macrophage/lymphocyte cellular axis and the tissue networks of cytokines.

Clinical insights and basic science correlates in sarcoidosis

More than a century has elapsed since the initial description of sarcoidosis, but critical aspects of the disorder remain poorly understood. Information obtained from epidemiologic observations and basic laboratory research suggests that the disease may represent an immunologic response to an exogenous agent in a genetically susceptible individual. However, a definitive etiologic role for any specific exogenous agent has never been proved, and a "candidate gene" underlying a predisposition to sarcoidosis has not yet been identified. This review presents an historical framework for considering available evidence regarding a transmissible agent in sarcoidosis and host susceptibility to the disease.

Comparison of the T cell patterns in leprous and cutaneous sarcoid granulomas. Presence of Valpha24-invariant natural killer T cells in T-cell-reactive leprosy together with a highly biased T cell receptor Valpha repertoire

The T-cell-reactive (eg, tuberculoid and reversal) forms of leprosy represent a well-defined granulomatous reaction pattern against an invading pathogen. The immune response in cutaneous sarcoidosis is a granulomatous condition that pathologically is very similar to T-cell reactive leprosy. However, it lacks a defined causative agent. In view of the role of NKT cells in murine granulomas induced by mycobacterial cell walls, we have searched for the presence of NKT cells in the cutaneous lesions of both leprosy and sarcoidosis. These cells were present in T-cell-reactive leprosy but were undetectable in cutaneous sarcoidosis. We have also studied the TCR Valpha repertoire in the two diseases. In addition to Valpha24(+) NKT cells, all patients with T-cell-reactive leprosy showed a very restricted T-cell-reactive Valpha repertoire with a strong bias toward the use of the Valpha6 and Valpha14 segments. Valpha6 and Valpha14(+) T cells were polyclonal in terms of CDR3 length and Jalpha usage. In contrast, most sarcoidosis patients showed a diverse usage of Valpha chains associated with clonal or oligoclonal expansions reminiscent of antigen-driven activation of conventional T cells. Thus the origin and perpetuation of the two kinds of granulomatous lesions appear to depend on altogether distinct T-cell recruiting mechanisms.

New pathogenetic insights into the sarcoid granuloma

Although the most important enigma of sarcoidosis, ie, its etiology, remains an unsolved problem, the past few years have seen remarkable advances in understanding general immunologic and molecular aspects of the mechanisms leading to granuloma formation in sarcoidosis. It is now clear that during the sarcoid inflammatory process several cytokines are secreted at sites of disease activity; in addition, high affinity receptors for cytokines participating in the granuloma development have been recently identified. This article provides a detailed description of recent data that have clarified cellular interactions governing the dynamics of granuloma formation in sarcoidosis. Together, these new results provide important insights that can refocus efforts at developing immunotherapeutic methods of inhibiting cytokine production at sites of granuloma formation.

Design of a case control etiologic study of sarcoidosis (ACCESS). ACCESS Research Group

Sarcoidosis is a chronic granulomatous disorder of unknown cause, characterized by activation of T-lymphocytes and macrophages. A Case Control Etiologic Study of Sarcoidosis (ACCESS) is a multicenter study designed to determine the etiology of sarcoidosis. The study organization includes 10 Clinical Centers, a Clinical Coordinating Center, specialized Core Laboratories, a Central Specimen Repository, and a Project Office at the National Heart, Lung, and Blood Institute. In addition to etiology, ACCESS will examine the socioeconomic status and clinical course of patients with sarcoidosis. We propose to enroll 720 newly diagnosed cases of sarcoidosis and compare them to 720 age, sex, and race matched controls and follow the first 240 cases for two years. Leads to the etiology of sarcoidosis have come from diverse sources: in clinical laboratory investigations, alveolitis has been found to precede granulomatous inflammation; in case control studies, familial aggregation has been identified; and in case reports, recurrence of granulomatous inflammation has been observed after lung transplantation. We describe the rationale for the study design based on genetic, environmental, infectious, and immune dysregulation hypotheses and the methods used for selecting controls. The cause may not prove to be a single, known exposure. Interactions of exposures with genetic predispositions would have important implications for our understanding of immune responses as well as the pathogenesis of sarcoidosis.

Identification of Pathogenic T Cells in Patients with Beryllium-Induced Lung Disease

Chronic beryllium disease (CBD) is caused by beryllium exposure and is characterized by granulomatous inflammation with accumulation of CD4+ T cells in the lung. We analyzed TCR β-chain and α-chain genes expressed by these CD4+ T cells. In the lungs of individual patients, as well as among four of five CBD patients studied, different oligoclonal expansions within the Vβ3 subset were found to express homologous or even identical CDR3 amino acid sequences. These related expansions were specific for CBD patients, were compartmentalized to lung, and persisted at high frequency in patients with active disease. Limiting dilution cloning and analysis of coexpressed TCR α-chain genes confirmed that these TCRs were selectively expanded by a common Ag involving beryllium. Overall, homologous TCR β- and α-chains showed identical V regions and invariant charged residues within the CDR3 but considerable variability in TCRJ usage. Remarkably, CBD patients expressing nearly identical TCRs did not share common HLA-DRB1 or DQ alleles. These results implicate particular CD4+ cells in the pathogenesis of CBD and provide insight into how beryllium is recognized in human disease.

Characterization of T-Cell Repertoire of the Bone Marrow in Immune-Mediated Aplastic Anemia: Evidence for the Involvement of Antigen-Driven T-Cell Response in Cyclosporine-Dependent Aplastic Anemia

To determine whether the antigen-driven T-cell response is involved in the pathogenesis of aplastic anemia (AA), we examined the complementarity-determining region 3 (CDR3) size distribution of T-cell receptor (TCR) β-chain (BV) subfamilies in the bone marrow (BM) of untreated AA patients. AA patients who did not respond to immunosuppressive therapy and those who obtained unmaintained remission early after cyclosporine (CyA) or antithymocyte globulin (ATG) therapy exhibited essentially a normal CDR3 size pattern. In contrast, five patients who needed continuous administration of CyA to maintain remission exhibited a skewed CDR3 size pattern in a number (>40%) of BV subfamilies suggestive of clonal predominance. The skewing of CDR3 size distribution became less pronounced in one of the CyA-dependent patients when the patient achieved unmaintained remission after a 4-year therapy with CyA, whereas it persisted longer than 7 years in the other patient requiring maintenance therapy. Sequencing of BV15 cDNA for which the CDR3 size pattern exhibited apparent clonal predominance in all CyA-dependent patients showed high homology of the amino acid sequence of the CDR3 between two different patients. These findings indicate that antigen-driven expansion of T cells is involved in the pathogenesis of AA characterized by CyA-dependent recovery of hematopoiesis.

Characterization of T-Cell Repertoire of the Bone Marrow in Immune-Mediated Aplastic Anemia: Evidence for the Involvement of Antigen-Driven T-Cell Response in Cyclosporine-Dependent Aplastic Anemia

To determine whether the antigen-driven T-cell response is involved in the pathogenesis of aplastic anemia (AA), we examined the complementarity-determining region 3 (CDR3) size distribution of T-cell receptor (TCR) β-chain (BV) subfamilies in the bone marrow (BM) of untreated AA patients. AA patients who did not respond to immunosuppressive therapy and those who obtained unmaintained remission early after cyclosporine (CyA) or antithymocyte globulin (ATG) therapy exhibited essentially a normal CDR3 size pattern. In contrast, five patients who needed continuous administration of CyA to maintain remission exhibited a skewed CDR3 size pattern in a number (&gt;40%) of BV subfamilies suggestive of clonal predominance. The skewing of CDR3 size distribution became less pronounced in one of the CyA-dependent patients when the patient achieved unmaintained remission after a 4-year therapy with CyA, whereas it persisted longer than 7 years in the other patient requiring maintenance therapy. Sequencing of BV15 cDNA for which the CDR3 size pattern exhibited apparent clonal predominance in all CyA-dependent patients showed high homology of the amino acid sequence of the CDR3 between two different patients. These findings indicate that antigen-driven expansion of T cells is involved in the pathogenesis of AA characterized by CyA-dependent recovery of hematopoiesis.

Antibodies to the IL-12 Receptor β2 Chain Mark Human Th1 But Not Th2 Cells In Vitro and In Vivo

Great attention has been placed on the possibility of distinguishing Th1 from Th2 cells on the basis of differential expression of surface receptors. We have recently shown that the differential expression of the IL-12Rβ2 chain in Th1 and Th2 cells, as measured at the mRNA level, accounts for an important regulatory mechanism in the differentiation of the two cell subsets. In this study, we identify IL-12R expression at the protein level. We have generated an anti-IL-12Rβ2-specific mAb and analyzed IL-12Rβ2 expression on polarized Th cell populations generated in vitro and on T cells derived from patients with Th1- or Th2-mediated inflammatory conditions. Although IL-12Rβ2 was absent in freshly isolated PBMC and in cord blood cells, we were able to detect IL-12Rβ2 expression selectively in differentiated Th1 and T cytotoxic 1, but not Th2 or T cytotoxic 2 cells. In the presence of IL-12, cell surface expression of the IL-12Rβ2 subunit was readily detected on T cells after 24 h, reached the maximum at day 5, and declined thereafter. Most importantly, the anti-IL-12Rβ2 mAb recognizes lung T cells from patients with sarcoidosis, a disease characterized by a typical cell-mediated, Th1-type inflammatory response. In contrast, IL-12Rβ2 was absent in lung T cells from patients with allergic asthma, a disease characterized by a Th2-type inflammatory response. The mAb reported in this study should represent a powerful tool to investigate the role of Th1 and Th2 cells in inflammatory conditions and to monitor therapies aimed at altering the balance of Th cell subsets.