T-cell activation profiles in different granulomatous interstitial lung diseases--a role for CD8+CD28(null) cells?

T-cell senescence: A crucial player in autoimmune diseases

Senescent T cells are proliferative disabled lymphocytes that lack antigen-specific responses. The development of T-cell senescence in autoimmune diseases contributes to immunological disorders and disease progression. Senescent T cells lack costimulatory markers with the reduction of T cell receptor repertoire and the uptake of natural killer cell receptors. Senescent T cells exert cytotoxic effects through the expression of perforin, granzymes, tumor necrosis factor, and other molecules without the antigen-presenting process. DNA damage accumulation, telomere damage, and limited DNA repair capacity are important features of senescent T cells. Impaired mitochondrial function and accumulation of reactive oxygen species contribute to T cell senescence. Alleviation of T-cell senescence could provide potential targets for the treatment of autoimmune diseases.

Bronchoalveolar Lavage Lymphocytes in the Diagnosis of Hypersensitivity Pneumonitis among Patients with Interstitial Lung Disease

Rationale: Hypersensitivity pneumonitis (HP) is an interstitial lung disease (ILD) characterized by inflammation and/or fibrosis in response to an inhalational exposure.Objectives: To determine the value of bronchoalveolar lavage (BAL) fluid lymphocyte cellular analysis in the detection of HP among patients with newly detected ILD.Methods: This systematic review was undertaken in the context of development of an American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax clinical practice guideline. The clinical question was, "should patients with newly detected ILD undergo BAL fluid lymphocyte analysis to diagnose HP?" MEDLINE, EMBASE, and the gray literature were searched through October 2019. Studies that reported the percentage of BAL fluid lymphocytes for various ILDs were selected for inclusion. Meta-analyses compared the mean percentage of BAL fluid lymphocytes among patients with HP with that among patients with idiopathic pulmonary fibrosis (IPF) or sarcoidosis. The sensitivity and specificity by which various percentages of BAL fluid lymphocytes distinguish HP from IPF and sarcoidosis were also evaluated.Results: Eighty-four articles were selected. No randomized trials or observational studies were identified that compared BAL fluid lymphocyte analysis with no BAL fluid lymphocyte analysis in patients with ILD. Included studies were case series describing BAL fluid cell differentials in patients with various ILDs. The percentage of BAL fluid lymphocytes was significantly higher in both fibrotic and nonfibrotic HP compared with IPF. Similarly, the percentage of BAL fluid lymphocytes was significantly higher in both fibrotic and nonfibrotic HP compared with sarcoidosis. A threshold of 20% BAL fluid lymphocytes distinguished fibrotic HP from IPF with a sensitivity and specificity of 69% and 61%, respectively, and nonfibrotic HP from IPF with a sensitivity and specificity of 95% and 61%, respectively. It distinguished fibrotic HP from sarcoidosis with a sensitivity and specificity of 69% and 26%, respectively, and nonfibrotic HP from sarcoidosis with a sensitivity and specificity of 95% and 26%, respectively.Conclusions: The percentage of BAL fluid lymphocytes is higher in HP than IPF or sarcoidosis. However, a threshold that distinguishes HP from IPF or sarcoidosis with both high sensitivity and high specificity was not identified.

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

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

Diagnosis of Hypersensitivity Pneumonitis in Adults. An Official ATS/JRS/ALAT Clinical Practice Guideline

Background: This guideline addresses the diagnosis of hypersensitivity pneumonitis (HP). It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax.Methods: Systematic reviews were performed for six questions. The evidence was discussed, and then recommendations were formulated by a multidisciplinary committee of experts in the field of interstitial lung disease and HP using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach.Results: The guideline committee defined HP, and clinical, radiographic, and pathological features were described. HP was classified into nonfibrotic and fibrotic phenotypes. There was limited evidence that was directly applicable to all questions. The need for a thorough history and a validated questionnaire to identify potential exposures was agreed on. Serum IgG testing against potential antigens associated with HP was suggested to identify potential exposures. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. For patients with fibrotic HP, suggestions were made in favor of obtaining BAL for lymphocyte cellular analysis, transbronchial lung cryobiopsy, and surgical lung biopsy. Diagnostic criteria were established, and a diagnostic algorithm was created by expert consensus. Knowledge gaps were identified as future research directions.Conclusions: The guideline committee developed a systematic approach to the diagnosis of HP. The approach should be reevaluated as new evidence accumulates.

Enhanced CD8+ cytolytic T cell responses in the peripheral circulation of patients with sarcoidosis and non-Löfgren's disease

BACKGROUND

The role of CD4⁺ T cells in the immunopathogenesis of pulmonary sarcoidosis is well-established, while less is known about the phenotype and function of CD8⁺ cytolytic T cells (CTLs).

METHODS

CD8⁺ CTLs were explored in peripheral blood and bronchoalveolar lavage (BAL) samples obtained from up to 25 patients with sarcoidosis and 25 healthy controls. The proportion of CTLs was assessed by the expression of cytolytic effector molecules perforin, granzyme B and granulysin in CD8⁺ T cells, using flow cytometry. Cytolytic function in blood lymphocytes was assessed using a standard ⁵¹Cr-release assay. Patients with Löfgren´s syndrome (LS) and an acute disease onset, were compared to non-LS patients with an insidious onset.

RESULTS

Higher proportions of peripheral CD8⁺ CTLs expressing perforin and granzyme B were observed in sarcoidosis compared to healthy controls. Blood CTLs from non-LS patients had significantly higher expression of perforin, granzyme B and granulysin compared to matched BAL, while LS patients maintained lower levels of effector molecules in both compartments. Mitogen-stimulated peripheral lymphocytes from sarcoidosis patients, particularly from the non-LS group, showed a higher target cell lysis compared to controls.

CONCLUSION

These results demonstrated enhanced peripheral CD8⁺ CTL responses in sarcoidosis, especially in non-LS patients who have an increased risk of chronic disease. Further comprehensive clinical studies are warranted to increase our understanding of CD8⁺ CTL responses in sarcoidosis.

Increased T cell activation in BALF from children with Mycoplasma pneumoniae pneumonia

BACKGROUND AND OBJECTIVE

The mechanisms of Mycoplasma pneumoniae induced lung inflammation are not clearly understood yet. This study investigated whether activated T cells in the airway contributed to the pulmonary inflammation in patients with severe Mycoplasma pneumoniae pneumonia (MPP).

METHODS

BALF were collected in all 45 patients with MPP (MPP, n = 45), including mild (Mild, n = 20) and severe (Severe, n = 25) group. BALF in 20 of all 25 severe cases with MPP at the recovery stage (Rec-severe, n = 20) were collected again. The control group consisted of 20 patients with airway foreign body aspiration (Con., n = 20). CD3+ T cells, CD69+, HLA-DR+, CD25+ on CD3+ T cells in BALF were determined by flow cytometry. Levels of IL-6, IL-10 in BALF were determined by ELISA, and percentage of neutrophils was counted.

RESULTS

A significant increased percentage of neutrophils and levels of IL-6 and IL-10, decreased percentage of CD3+ T cells, increased expressions of CD69+, HLA-DR+ or CD25+ on CD3+ T cells were observed in children with MPP compared with the control group (P < 0.05 or 0.01). Compared to mild group, the percentage of neutrophils, CD3+ CD25+, IL-6, and IL-10 were increased in children with severe MPP (P < 0.01 or 0.05). Compared to acute stage, an increased percentage of CD3+ T cells, decreased percentage of neutrophils and IL-6 level, and expressions of CD3+ CD69+ or CD3+ CD25+ were observed at the recovery stage in children with severe MPP (P < 0.01 or 0.05).

CONCLUSIONS

Increased activation of T cell in BALF may play an important role in the inflammatory response of acute and severe MPP. IL-6 may predict the severity and prognosis and provide a better assessment for patient care. However, the underlying mechanism awaits further detailed investigations.

Lymphocyte senescence in COPD is associated with loss of glucocorticoid receptor expression by pro-inflammatory/cytotoxic lymphocytes

Background

Glucocorticoid (GC) resistance is a major barrier in COPD treatment. We have shown increased expression of the drug efflux pump, Pgp1 in cytotoxic/pro-inflammatory lymphocytes in COPD. Loss of lymphocyte co-stimulatory molecule CD28 (lymphocyte senescence) was associated with a further increase in their pro-inflammatory/cytotoxic potential and resistance to GC. We hypothesized that lymphocyte senescence and increased Pgp1 are also associated with down-regulation of the GC receptor (GCR).

Methods

Blood was collected from 10 COPD and 10 healthy aged-matched controls. Flow cytometry was applied to assess intracellular pro-inflammatory cytokines, CD28, Pgp1, GCR, steroid binding and relative cytoplasm/nuclear GCR by CD28+ and CD28null T, NKT-like cells. GCR localization was confirmed by fluorescent microscopy.

Results

COPD was associated with increased numbers of CD28nullCD8+ T and NKT-like cells. Loss of CD28 was associated with an increased percentage of T and NKT-like cells producing IFNγ or TNFα and associated with a loss of GCR and Dex-Fluor staining but unchanged Pgp1. There was a significant loss of GCR in CD8 + CD28null compared with CD8 + CD28+ T and NKT-like cells from both COPD and controls (eg, mean ± SEM 8 ± 3% GCR + CD8 + CD28null T-cells vs 49 ± 5% GCR + CD8 + CD28+ T-cells in COPD). There was a significant negative correlation between GCR expression and IFNγ and TNFα production by T and NKT-like cells(eg, COPD: T-cell IFNγ R = −.615; ) and with FEV1 in COPD (R = −.777).

Conclusions

COPD is associated with loss of GCR in senescent CD28null and NKT-like cells suggesting alternative treatment options to GC are required to inhibit these pro-inflammatory/cytotoxic cells.

Overexpression of IL-17RC associated with ocular sarcoidosis

Background

Sarcoidosis is a chronic inflammatory disease with a systemic granulomatous disorder affecting multiple organs including the eye. Both CD4⁺ T cell and macrophage have been linked to the pathogenesis of the disease.

Methods

The expression of IL-17RC was measured using FACS,immunohistochemistry and real-time PCR. Serum level of IL-17 was detected using ELISA.

Results

An elevated expression of IL-17RC on CD8⁺ T cells in peripheral blood was found in patients with ocular sarcoidosis as compared to healthy controls. Interestingly, we found a significant increase in the serum level of IL-17 in patients with ocular sarcoidosis as compared to healthy controls, which may be responsible for the induction of IL-17RC on CD8⁺ cells. In addition, IL-17RC appeared only in the retinal tissue of the patient with clinically active sarcoidosis.

Conclusions

Our results suggested a potential involvement of IL-17RC⁺CD8⁺ T cells in pathogenesis of ocular sarcoidosis.

Activated CD8(+) T cells and NKT cells in BAL fluid improve diagnostic accuracy in sarcoidosis

PURPOSE

The clinical diagnosis of pulmonary sarcoidosis is based on the presence of noncaseating granulomas in an appropriate clinical setting with either bilateral hilar adenopathy and/or parenchymal infiltrates. Lymphocytosis with an increased CD4/CD8 T cell ratio in bronchoalveolar lavage fluid is supportive. We evaluated the diagnostic accuracy of a predictive binary logistic regression model in sarcoidosis based on sex, age, and bronchoalveolar lavage fluid cell profile with and without the inclusion of HLA-DR(+) CD8(+) T cells and natural killer T-cell fractions.

METHODS

A retrospective analysis of differential cell counts and lymphocyte phenotypes by flow cytometry in bronchoalveolar lavage was performed in 183 patients investigated for possible diffuse parenchymal lung disease. A logistic regression model with age, sex, lymphocyte fraction, eosinophils, and CD4/CD8 ratio in bronchoalveolar lavage fluid (basic model) was compared with a final model, which also included fractions of HLA-DR(+) CD8(+) T cells and natural killer T cells. Diagnostic accuracy of the two models was assessed by receiver operating characteristic (ROC) curves.

RESULTS

The area under the ROC curve for the basic and final model was 0.898 [95 % confidence interval (CI) 0.852-0.945] and 0.937 (95 % CI 0.902-0.972), respectively, p = 0.008.

CONCLUSIONS

Assessment of HLA-DR(+) CD8(+) T cell and natural killer T-cell fractions may improve diagnostic accuracy and further strengthen the importance of bronchoalveolar lavage in the diagnostic workup of sarcoidosis.

Is CD69 an effective brake to control inflammatory diseases?

Early studies described CD69 as a leukocyte activation marker, and suggested its involvement in the activation of different leukocyte subsets as well as in the pathogenesis of chronic inflammation. However, recent investigations have showed that CD69 knockout mice exhibit an enhanced or reduced susceptibility to different experimental models of inflammatory diseases, including those mediated by T helper 17 (Th17) lymphocytes. In this regard, the expression of CD69, both in Th17 lymphocytes and by a subset of regulatory T cells, has an important role in the control of the immune response and the inflammatory phenomenon. Therefore, different evidence indicates that CD69 exerts a complex immunoregulatory role in humans, and that it could be considered as a target molecule for the therapy of immune-mediated diseases.

[Hypersensitivity pneumonitis related to Penicillium chrysogenum and mesophilic Streptomyces: the usefulness of the Medical Indoor Environment Councelor (MIEC)]

Hypersensitivity pneumonitis (HP) occurred after organic antigens inhalation at home is rare and the diagnosis is very often difficult. We report the case of a 55-year male patient with allergic asthma since childhood, well controlled with inhaled corticosteroids, twice hospitalized for respiratory distresses. The patient presented fever (39°C), dry cough, rapidly progressive dyspnea, chest pain and crackles. Blood gas analysis found a hypoxemia of 52 mmHg, and CT-scan showed ground glass images in the upper lobes. Respiratory function tests showed severe obstructive syndrome and a decrease of diffusion test. HP was suspected because the symptoms were triggered by domestic environmental. The Medical Indoor Environment Councelor (MIEC) visited the patient's house and camper and performed air and dust samples. Moldy walnuts were found in the camper. The identification of microorganisms present in the air and on the surfaces in the camper was used for serum precipitins research by double diffusion (DD) and electrosyneresis (E) methods. From the 14 antigens tested, serological tests were considered significant for mesophilic Streptomyces (five arcs DD, six arcs E) and Penicillium chrysogenum (one arc DD, four arcs E). After removal from the camper of the objects suspected to be contaminated, the patient's symptoms regressed. This is a typical case of domestic HP to mesophilic Streptomyces and P. chrysogenum. The MIEC's intervention was useful in both diagnosis and treatment.

[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.

Management of hypersensivity pneumonitis

Hypersensitivity pneumonitis (HP) is an interstitial lung disease due to a combined type III and IV reaction with a granulomatous inflammation, caused by cytotoxic delayed hypersensitivity lymphocytes, in a Th1/Th17 milieu, chaperoned by a deficient suppressor function of T regulatory cells. Skewing toward a Th2 phenotype is reported for chronic HP. Phenotypic expression and severity depends on environmental and/or host genetic and immune co-factors. The wide spectrum of causative antigens is continuously up-dated with new sources of airborne organic particles and drug-induced HP. The diagnosis requires a detailed history, measurement of environmental exposure, pulmonary function tests, imaging, detection of serum specific antibodies, broncho-alveolar lavage, antigen-induced lymphocyte proliferation, environmental or laboratory-controlled inhalation challenge and lung biopsy. Complete antigen avoidance is the best therapeutic measure, although very difficult to achieve in some cases. Systemic steroids are of value for subacute and chronic forms of HP, but do not influence long term outcome. Manipulation of the immune response in HP holds future promise.

Bronchoalveolar lavage cell pattern from healthy human lung

Bronchoalveolar lavage (BAL) is widely accepted as a key diagnostic procedure in interstitial lung diseases (ILD). We performed a study to obtain reference intervals of differential cell patterns in BAL fluid with special attention to the origin of lavage fluid, e.g. bronchial/alveolar, to atopy and smoking status and to age of the healthy people. We performed bronchoalveolar lavage in 55 healthy subjects with known atopy status (age: 18-64 years, non-smokers/smokers: 34/21) and determined differential cell counts and lymphocyte subsets in BAL fluid and blood. Moreover, in a subgroup of non-smoking healthy individuals we measured the expression of the regulatory T cell marker forkhead box protein 3 (FoxP3) on blood and BAL fluid lymphocytes in addition to a comprehensive set of activation markers. Differential cell counts from the alveolar lavage fraction differed significantly from calculated pooled fractions (n = 11). In contrast, marginal differences were found between atopic and non-atopic subjects. Interestingly, the BAL fluid CD4(+) /CD8(+) ratio correlated strongly with age (r(2) = 0·50, P < 0·0001). We consider the bronchial and alveolar fraction to be lavage fluid from fundamentally different compartments and recommend analysis of the alveolar fraction in diagnostic work-up of ILD. In addition, our data suggest that age corrected BAL fluid CD4(+) /CD8(+) ratios should be used in the clinical evaluation of patients with interstitial lung diseases.

Peripheral blood responses to specific antigens and CD28 in sarcoidosis

BACKGROUND

Potential antigens inducing sarcoid inflammation include mycobacterial and auto-antigens. Paradoxically, peripheral anergy to common recall antigens also occurs, possibly due to impaired dendritic cell or regulatory T-cell responses, or impaired T-cell co-stimulation. The purpose of this study was to compare peripheral blood responses of patients with sarcoidosis to candidate antigens, and examine CD28 T-cell co-stimulation.

METHODS

Peripheral blood mononuclear cell (PBMC) responses were examined from patients with sarcoidosis (n=16) and healthy control subjects (n=22) following PBMC stimulation with: anti-CD3/CD28 coated beads; Mycobacterium tuberculosis ESAT-6 and KatG peptides; vimentin and lysyl tRNA peptides; and common recall antigens, including cytomegalovirus (CMV) cell lysate as well as CMV, Epstein-Barr virus, influenza virus (CEF) peptides.

RESULTS

ESAT-6/KatG peptide stimulation induced greater numbers of IFN-γ producing T-cells, and elevated IL-2, IL-6 and TNF-α production in sarcoidosis compared to purified protein derivative (PPD)-negative healthy control subjects. PBMCs from patients with sarcoidosis showed reduced IFN-γ producing T-cells following stimulation with CMV lysate, CEF peptides and CD3/CD28 beads; and reduced IL-4 and TNF-α production following CD3/CD28 activation.

CONCLUSIONS

Patients with sarcoidosis exhibit greater PBMC responses to M. tuberculosis antigens compared to PPD-negative controls, but reduced T-cell responses to common recall antigens. One contributing mechanism may be impairment of T-cell CD28 co-stimulation.

Multiparameter phenotyping of T-cell subsets in distinct subgroups of patients with pulmonary sarcoidosis

OBJECTIVES

  Sarcoidosis is an inflammatory disorder in which elevated numbers of activated T cells are found in the lung. HLA-DRB1*0301(pos) (DR3(pos) ) patients are characterized by good prognosis and an accumulation of lung CD4(pos) T cells expressing the T-cell receptor (TCR) gene segment AV2S3. Our aim was to phenotype lung and blood T-cell subsets in distinct patient groups to better understand the function of these subsets.

DESIGN

  Bronchoalveolar lavage (BAL) fluid and whole blood were obtained from a total of 22 patients with sarcoidosis, of whom 11 were DR3(pos) . Using eight-colour flow cytometry, phenotyping of T cells was performed with regard to CD3, CD4, CD8, CD25, CD27, CD45RO, CD57, CD69, CD103, FOXP3 and TCR AV2S3.

RESULTS

  DR3(pos) patients had fewer FOXP3(pos) (regulatory) CD45RO(pos) (memory) BAL T cells than DR3(neg) patients. Fewer AV2S3(pos) T cells were FOXP3(pos) , compared with AV2S3(neg) cells, thus indicating an effector function and not a regulatory role for this subset. Fewer lung and blood AV2S3(pos) T cells were CD25(pos)  CD27(pos) , and more were CD25(neg)  CD27(neg) and CD69(pos) , compared with AV2S3(neg) T cells, indicating a higher degree of differentiation and activation in both compartments.

CONCLUSION

  Our main findings were a lower proportion of regulatory T cells in DR3(pos) patients, together with the accumulation of AV2S3(pos) T cells with a highly activated effector phenotype in the lungs of these patients. This may provide for efficient elimination of a harmful antigen in DR3(pos) patients and could thus help to explain the spontaneous recovery typically seen in these patients.

Role of increased CD8/CD28(null) T cells and alternative co-stimulatory molecules in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease; it is a leading cause of death and existing treatments have no proven disease-modifying effect. The mechanisms underlying this resistance are largely unknown, but suggest the presence of some self-maintaining pathogenic process, possibly initiated by cigarette smoking, that prevents the normal resolution of inflammation. We have previously reported increased production of proinflammatory cytokines and granzyme b by CD8(+) T cells in COPD; costimulatory receptor/ligand interactions required include CD80:86/CD28, B7-1/CTLA4, 4-1BB/1BBL and OX40/OX40L. We hypothesized that a dysregulated expression/function of these molecules may play a role in inflammatory/autoimmune components of COPD. We analysed T cell co-stimulatory molecules in blood from 34 controls, 15 smokers and 48 COPD subjects. We assessed the potential functional relevance of CD8/CD28(null) cells in COPD by measuring their production of proinflammatory cytokines, co-stimulatory molecules, granzyme and perforin. A smoke-exposed murine model was applied to investigate the relative expression of CD8/CD28(null) T cells in blood, lung tissue and airway. CD8/CD28(null) cells were increased in both current- and ex-smoker COPD groups; these cells expressed significantly more interferon (IFN)-γ, OX40, 4-1BB, CTLA4, granzyme and perforin when stimulated than CD8/CD28(+) T cells. There were no changes in CD4/CD28(null) T cells. In mice exposed to cigarette smoke for 12 weeks, CD8/CD28(null) T cells were significantly increased in the airway with a trend for an increase in lung tissue and blood. Increased production of proinflammatory cytokines and expression of alternative co-stimulatory molecules by CD8/CD28(null) T cells may play a role in inflammatory or autoimmune responses in COPD and identify therapeutic targets.

Toll-like receptor (TLR)-9 genetics and function in sarcoidosis

Sarcoidosis is a systemic disorder characterized by the formation of non-caseating granulomas in variable organs. Toll-like receptor (TLR)-9 is important in the innate immune response against both Mycobacterium tuberculosis and Propionibacterium acnes, candidate causative agents in sarcoidosis. The aim of our study was to investigate possible genetic and functional differences in TLR-9 between patients and controls. TLR-9 single nucleotide polymorphisms were genotyped in 533 patients and divided into a study cohort and validation cohort and 185 healthy controls. Furthermore, part of the promotor as well as the entire coding region of the TLR-9 gene were sequenced in 20 patients in order to detect new mutations. No genetic differences were found between patients and controls. In order to test TLR-9 function, peripheral blood mononuclear cells (PBMCs) of 12 healthy controls and 12 sarcoidosis patients were stimulated with a TLR-9 agonist and the induction of interleukin (IL)-6, interferon (IFN)-γ and IL-23 was measured. Sarcoidosis patients produce significantly less IFN-γ upon stimulation with different stimuli. Regarding IL-23 production, a significant difference between patients and controls was found only after stimulation with the TLR-9 agonist. In conclusion, we did not find genetic differences in the TLR-9 gene between sarcoidosis patients and controls. Sarcoidosis patients produce less IFN-γ regardless of the stimulating agent, probably reflecting the anergic state often seen in their peripheral blood T lymphocytes. The differences in TLR-9-induced IL-23 production could indicate that functional defects in the TLR-9 pathway of sarcoidosis patients play a role in disease susceptibility or evolution.