Follicular Helper-like T Cells in the Lung Highlight a Novel Role of B Cells in Sarcoidosis

Activation and maturation of antigen-specific B cells in nonectopic lung infiltrates are independent of germinal center reactions in the draining lymph node

Pulmonary T and B cells are important for protection of this mucosal barrier site. While viral infections lead to the development of ectopic lymphoid structures highly similar to those in germinal centers in secondary lymphoid organs, little is known about how T/B cooperation occurs in the unstructured, diffuse tissue infiltrates characteristic of autoimmune diseases and nonviral infections. Using a mouse model of interstitial lung inflammation, we found that naive B cells are directly activated in lung tissue. Despite the absence of any germinal center-like structures, the interaction of B cells with peripheral T helper cells results in efficient somatic hypermutation and class switching. As antigen-presenting cells, macrophages are critical for this process. Unique B-cell repertoires indicated that the lung response was autonomous from the lung-draining lymph node. Only lung GC-like B cells were switched to IgA and had a broader repertoire, making them ideal candidates for producing broadly neutralizing immunoglobulins against respiratory pathogens.

Follicular helper T cells in Graves' disease: pathogenic mechanisms and therapeutic implications

Graves' disease (GD) is a specific autoimmune disorder that primarily affects the thyroid gland, leading to thyrotoxicosis and potentially accompanied by extrathyroidal manifestations such as Graves' ophthalmopathy and pretibial myxedema. Its pathogenesis involves the abnormal proliferation of autoreactive B cells, which subsequently produce autoantibodies targeting the thyroid-stimulating hormone receptor (TSHR), resulting in excessive secretion of thyroid hormones. Helper T cells (Th cells) play a significant role in this process. In recent years, follicular helper T cells (Tfh cells) have been identified as a novel subset of Th cells, primarily residing in the germinal centers (GCs) of lymphoid organs and in peripheral blood. Tfh cells facilitate B cell development and antibody production, thus playing a crucial role in the pathogenesis of GD. Their aberrant proliferation and function may lead to the production of autoantibodies and pathological processes such as tissue damage. This review summarizes the latest advancements in the biology of Tfh cells and their role in GD, exploring their potential as therapeutic targets, thereby providing new insights into the pathogenesis and treatment of GD.

Insights on immune profile, pathogenesis and differential diagnosis of hypersensitivity pneumonitis and pulmonary sarcoidosis-A holistic review and bibliometric analysis

Hypersensitivity pneumonitis (HP) and sarcoidosis are granulomatous interstitial lung diseases with overlapping clinical and immunological features, posing diagnostic and therapeutic challenges. This review offers a comprehensive assessment of their immune mechanisms, etiology, and pathogenesis. HP is predominantly triggered by exposure to environmental antigens, while sarcoidosis involves an exaggerated immune response to elusive antigens. Both diseases are driven by Th1 and Th17 pathways, regulatory T-cell dysfunction, and cytokine-mediated granuloma formation. Emerging diagnostic and prognostic biomarkers, such as KL-6, GDF15, PD-1, TIGIT, and genetic regulators including m6A and m5C modifications, provide valuable insights for disease stratification. Incorporating findings from a total of 38 studies (HP: n = 13; sarcoidosis: n = 25) published in the last 5 years, this review highlights key immune regulatory mechanisms, identifies critical research gaps, and provides directions for improving differential diagnosis. Addressing these gaps through multi-omics integration, computational tools, and interdisciplinary collaboration holds significant potential for refining diagnostic accuracy, advancing therapeutic strategies, and improving patient outcomes in both HP and sarcoidosis.

Diagnostic Biomarkers for Uveitis: Serum BAFF and CXCL9 in Differentiating Ocular Sarcoidosis, Tuberculosis and Other Entities with Implication for QuantiFERON-Positive Uveitis

PURPOSE

To evaluate serum B cell activating factor (BAFF) and CXCL9 as diagnostic biomarkers for ocular sarcoidosis and ocular tuberculosis (TB). We also explore their role in the stratification of patients with QuantiFERON (QFT)-positive uveitis without another identifiable cause.

METHODS

Eighty uveitis patients with various entities were included: 10 with ocular sarcoidosis, 35 with TB-related uveitis (including 11 confirmed (ocular TB) and 24 QFT-positive uveitis of unknown cause) and 35 with other uveitis entities. Levels of serum BAFF and CXCL9 were measured.

RESULTS

Serum BAFF was higher in ocular sarcoidosis compared to other groups (area under the curve (AUC) = 0.74; 95% CI: 0.53-0.96, p = 0.017). At an optimal serum BAFF cut-off point of 772.3 pg/ml, the sensitivity was 70.0% (95% CI: 39.7-89.2) and the specificity was 89.1% (95% CI: 77.0-95.3). Serum CXCL9 was comparable between ocular sarcoidosis and confirmed ocular TB but was significantly higher in these groups compared to other uveitis entities (AUC = 0.71, 95% CI: 0.57-0.86, p = 0.011). To differentiate ocular sarcoidosis and TB from other uveitis entities, CXCL9 (cutoff: 105.5 pg/ml) showed a sensitivity of 88.9% (95% CI: 67.2-98.0) and a specificity of 54.3% (95% CI: 38.2-69.5). High CXCL9 TB-related uveitis patients demonstrated a higher proportion of uveitis resolution when fully treated with antitubercular treatment (ATT) (p = 0.027).

CONCLUSIONS

Serum BAFF and CXCL9 serve as potential diagnostic biomarkers for differentiating ocular sarcoidosis, ocular TB and other uveitis entities. These might identify QFT-positive uveitis who are most in need of ATT.

T cell-B cell interactions in human autoimmune diseases

Activation of autoreactive B cells and production of specific autoantibodies are hallmark features of many autoimmune diseases. B cell differentiation into antibody-secreting cells typically requires help from cognate T cells, which provide both cytokines and cell surface signals in an intricate intercellular interaction. A range of T cells can provide this help to B cells, including T follicular helper cells in follicles of secondary lymphoid organs, as well as T peripheral helper cells, which accumulate within inflamed target tissues in autoimmune diseases. Here, we discuss recent observations about the phenotypes of B cell-helper T cells that accumulate in inflamed tissues and in circulation of patients with autoimmune diseases, the correlations between B cell-helper T cells and B cells in these tissues, and key mediators of productive T cell-B cell interactions, with a focus on mediators that are being targeted therapeutically. Understanding the scope of B cell-helper T cells and their functions will improve our ability to quantify and track pathologic T cell-B cell interactions in human autoimmune diseases and may highlight critical mediators that can be targeted to suppress these interactions therapeutically.

Full-length mRNA sequencing resolves novel variation in 5' UTR length for genes expressed during human CD4 T-cell activation

Isoform sequencing (Iso-Seq) uses long-read technology to produce highly accurate full-length reads of mRNA transcripts. Visualization of individual mRNA molecules can reveal new details of transcript variation within understudied portions of mRNA, such as the 5' untranslated region (UTR). Differential 5' UTRs may contain motifs, upstream open reading frames (uORFs), and secondary structures that can serve to regulate translation or further indicate changes in promoter usage, where transcriptional control may impact protein expression levels. To begin to explore isoform variation during T-cell activation, we generated the first Iso-Seq reference transcriptome of activated human CD4 T cells. Within this dataset, we discovered many novel splice- and end-variant transcripts. Remarkably, one in every eight genes expressed in our dataset was found to have a notable proportion of transcripts with 5' UTR lengthened by over 100 bp compared to the longest corresponding UTR within the Gencode dataset. Among these end-variant transcripts, two novel isoforms were identified for CXCR5, a chemokine receptor associated with T follicular helper cell (Tfh) function and differentiation. When investigated in a model cell system, these lengthened UTR conferred reduced transcript stability and, for one of these isoforms, short uORFs introduced by the added length altered protein expression kinetics. This study highlights instances in which current reference databases are incomplete relative to the information obtained by long-read sequencing of intact mRNA. Iso-Seq is thus a promising approach to better understanding the plasticity of promoter usage, alternative splicing, and UTR sequences that influence RNA stability and translation efficiency.

The immunopathogenesis of sarcoidosis

Sarcoidosis is a granulomatous multiorgan disease, thought to result from exposure to yet unidentified antigens in genetically susceptible individuals. The exaggerated inflammatory response that leads to granuloma formation is highly complex and involves the innate and adaptive immune system. Consecutive immunological studies using advanced technology have increased our understanding of aberrantly activated immune cells, mediators and pathways that influence the formation, maintenance and resolution of granulomas. Over the years, it has become increasingly clear that disease immunopathogenesis can only be understood if the clinical heterogeneity of sarcoidosis is taken into consideration, along with the distribution of immune cells in peripheral blood and involved organs. Most studies offer an immunological snapshot during disease course, while the cellular composition of both the circulation and tissue microenvironment may change over time. Despite these challenges, novel insights on the role of the immune system are continuously published, thus bringing the field forward. This review highlights current knowledge on the innate and adaptive immune responses involved in sarcoidosis pathogenesis, as well as the pathways involved in non-resolving disease and fibrosis development. Additionally, we describe proposed immunological mechanisms responsible for drug-induced sarcoid like reactions. Although many aspects of disease immunopathogenesis remain to be unraveled, the identification of crucial immune reactions in sarcoidosis may help identify new treatment targets. We therefore also discuss potential therapies and future strategies based on the latest immunological findings.

Differential Diagnosis of Tuberculosis and Sarcoidosis by Immunological Features Using Machine Learning

Despite the achievements of modern medicine, tuberculosis remains one of the leading causes of mortality globally. The difficulties in differential diagnosis have particular relevance in the case of suspicion of tuberculosis with other granulomatous diseases. The most similar clinical and radiologic changes are sarcoidosis. The aim of this study is to apply mathematical modeling to determine diagnostically significant immunological parameters and an algorithm for the differential diagnosis of tuberculosis and sarcoidosis. Materials and methods: The serum samples of patients with sarcoidosis (SD) (n = 29), patients with pulmonary tuberculosis (TB) (n = 32) and the control group (n = 31) (healthy subjects) collected from 2017 to 2022 (the average age 43.4 ± 5.3 years) were examined. Circulating 'polarized' T-helper cell subsets were analyzed by multicolor flow cytometry. A symbolic regression method was used to find general mathematical relations between cell concentrations and diagnosis. The parameters of the selected model were finally fitted through multi-objective optimization applied to two conflicting indices: sensitivity to sarcoidosis and sensitivity to tuberculosis. Results: The difference in Bm2 and CD5-CD27- concentrations was found to be more significant for the differential diagnosis of sarcoidosis and tuberculosis than any individual concentrations: the combined feature Bm2 - [CD5-CD27-] differentiates sarcoidosis and tuberculosis with p < 0.00001 and AUC = 0.823. An algorithm for differential diagnosis was developed. It is based on the linear model with two variables: the first variable is the difference Bm2 - [CD5-CD27-] mentioned above, and the second is the naïve-Tregs concentration. The algorithm uses the model twice and returns "dubious" in 26.7% of cases for patients with sarcoidosis and in 16.1% of cases for patients with tuberculosis. For the remaining patients with one of these two diagnoses, its sensitivity to sarcoidosis is 90.5%, and its sensitivity to tuberculosis is 88.5%. Conclusions: A simple algorithm was developed that can distinguish, by certain immunological features, the cases in which sarcoidosis is likely to be present instead of tuberculosis. Such cases may be further investigated to rule out tuberculosis conclusively. The mathematical model underlying the algorithm is based on the analysis of "naive" T-regulatory cells and "naive" B-cells. This may be a promising approach for differential diagnosis between pulmonary sarcoidosis and pulmonary tuberculosis. The findings may be useful in the absence of clear differential diagnostic criteria between pulmonary tuberculosis and sarcoidosis.

Sarcoidosis versus Granulomatous and Lymphocytic Interstitial Lung Disease in Common Variable Immunodeficiency: A Comparative Review

Sarcoidosis and Granulomatous and Lymphocytic Interstitial Lung Diseases (GLILD) are two rare entities primarily characterised by the development of Interstitial Lung Disease (ILD) in the context of systemic immune dysregulation. These two conditions partially share the immunological background and pathologic findings, with granuloma as the main common feature. In this narrative review, we performed a careful comparison between sarcoidosis and GLILD, with an overview of their main similarities and differences, starting from a clinical perspective and ending with a deeper look at the immunopathogenesis and possible target therapies. Sarcoidosis occurs in immunocompetent individuals, whereas GLILD occurs in patients affected by common variable immunodeficiency (CVID). Moreover, peculiar extrapulmonary manifestations and radiological and histological features may help distinguish the two diseases. Despite that, common pathogenetic pathways have been suggested and both these disorders can cause progressive impairment of lung function and variable systemic granulomatous and non-granulomatous complications, leading to significant morbidity, reduced quality of life, and survival. Due to the rarity of these conditions and the extreme clinical variability, there are still many open questions concerning their pathogenesis, natural history, and optimal management. However, if studied in parallel, these two entities might benefit from each other, leading to a better understanding of their pathogenesis and to more tailored treatment approaches.

Recruitment of plasma cells from IL-21-dependent and IL-21-independent immune reactions to the bone marrow

Bone marrow plasma cells (BMPC) are the correlate of humoral immunity, consistently releasing antibodies into the bloodstream. It remains unclear if BMPC reflect different activation environments or maturation of their precursors. Here we define human BMPC heterogeneity and track the recruitment of antibody-secreting cells (ASC) from SARS-CoV-2 vaccine immune reactions to the bone marrow (BM). Trajectories based on single-cell transcriptomes and repertoires of peripheral and BM ASC reveal sequential colonisation of BMPC compartments. In activated B cells, IL-21 suppresses CD19 expression, indicating that CD19low-BMPC are derived from follicular, while CD19high-BMPC originate from extrafollicular immune reactions. In primary immune reactions, both CD19low- and CD19high-BMPC compartments are populated. In secondary immune reactions, most BMPC are recruited to CD19high-BMPC compartments, reflecting their origin from extrafollicular reactivations of memory B cells. A pattern also observable in vaccinated-convalescent individuals and upon diphtheria/tetanus/pertussis recall-vaccination. Thus, BMPC diversity reflects the evolution of a given humoral immune response.

Phenotypes and Serum Biomarkers in Sarcoidosis

Sarcoidosis is a multisystem disease, which is diagnosed on a compatible clinical presentation, non-necrotizing granulomatous inflammation in one or more tissue samples, and exclusion of alternative causes of granulomatous disease. Considering its heterogeneity, numerous aspects of the disease remain to be elucidated. In this context, the identification and integration of biomarkers may hold significance in clinical practice, aiding in appropriate selection of patients for targeted clinical trials. This work aims to discuss and analyze how validated biomarkers are currently integrated in disease category definitions. Future studies are mandatory to unravel the diverse contributions of genetics, socioeconomic status, environmental exposures, and other sociodemographic variables to disease severity and phenotypic presentation. Furthermore, the implementation of transcriptomics, multidisciplinary approaches, and consideration of patients' perspectives, reporting innovative insights, could be pivotal for a better understanding of disease pathogenesis and the optimization of clinical assistance.

Sarcoidosis-related autoimmune inflammation in COVID-19 convalescent patients

Currently, there are a large number of reports about the development of autoimmune conditions after COVID-19. Also, there have been cases of sarcoid-like granulomas in convalescents as a part of the post-COVID-19 syndrome. Since one of the etiological theories of sarcoidosis considers it to be an autoimmune disease, we decided to study changes in the adaptive humoral immune response in sarcoidosis and SARS-CoV-2 infection and to find out whether COVID-19 can provoke the development of sarcoidosis. This review discusses histological changes in lymphoid organs in sarcoidosis and COVID-19, changes in B cell subpopulations, T-follicular helper cells (Tfh), and T-follicular regulatory cells (Tfr), and analyzes various autoantibodies detected in these pathologies. Based on the data studied, we concluded that SARS-CoV-2 infection may cause the development of autoimmune pathologies, in particular contributing to the onset of sarcoidosis in convalescents.

HTLV-1 bZIP Factor-Induced Reprogramming of Lactate Metabolism and Epigenetic Status Promote Leukemic Cell Expansion

Acceleration of glycolysis is a common trait of cancer. A key metabolite, lactate, is typically secreted from cancer cells because its accumulation is toxic. Here, we report that a viral oncogene, HTLV-1 bZIP factor (HBZ), bimodally upregulates TAp73 to promote lactate excretion from adult T-cell leukemia-lymphoma (ATL) cells. HBZ protein binds to EZH2 and reduces its occupancy of the TAp73 promoter. Meanwhile, HBZ RNA activates TAp73 transcription via the BATF3-IRF4 machinery. TAp73 upregulates the lactate transporters MCT1 and MCT4. Inactivation of TAp73 leads to intracellular accumulation of lactate, inducing cell death in ATL cells. Furthermore, TAp73 knockout diminishes the development of inflammation in HBZ-transgenic mice. An MCT1/4 inhibitor, syrosingopine, decreases the growth of ATL cells in vitro and in vivo. MCT1/4 expression is positively correlated with TAp73 in many cancers, and MCT1/4 upregulation is associated with dismal prognosis. Activation of the TAp73-MCT1/4 pathway could be a common mechanism contributing to cancer metabolism.

SIGNIFICANCE

An antisense gene encoded in HTLV-1, HBZ, reprograms lactate metabolism and epigenetic modification by inducing TAp73 in virus-positive leukemic cells. A positive correlation between TAp73 and its target genes is also observed in many other cancer cells, suggesting that this is a common mechanism for cellular oncogenesis. This article is featured in Selected Articles from This Issue, p. 337.

Unveiling tumor immune evasion mechanisms: abnormal expression of transporters on immune cells in the tumor microenvironment

The tumor microenvironment (TME) is a crucial driving factor for tumor progression and it can hinder the body's immune response by altering the metabolic activity of immune cells. Both tumor and immune cells maintain their proliferative characteristics and physiological functions through transporter-mediated regulation of nutrient acquisition and metabolite efflux. Transporters also play an important role in modulating immune responses in the TME. In this review, we outline the metabolic characteristics of the TME and systematically elaborate on the effects of abundant metabolites on immune cell function and transporter expression. We also discuss the mechanism of tumor immune escape due to transporter dysfunction. Finally, we introduce some transporter-targeted antitumor therapeutic strategies, with the aim of providing new insights into the development of antitumor drugs and rational drug usage for clinical cancer therapy.

Imbalance of Lymphocyte Subsets and CD45RA-Expressing Cells in Intrathoracic Lymph Nodes, Alveolar Compartment and Bloodstream of Pulmonary Sarcoidosis Patients

Sarcoidosis is a systemic granulomatous disease mainly affecting the lungs and hilomediastinal lymph nodes. It is characterized by non-caseating epithelioid cell granulomas in lymph nodes and lungs. Our study aimed to evaluate and compare T, B and NK cell subsets in the alveolar compartment, lymph nodes and the bloodstream simultaneously in the same patients to elucidate the immune responses associated with the development and progression of sarcoidosis. A secondary aim was to evaluate the distribution of CD45RA-expressing cells in the different anatomical compartments. Patients suspected to have sarcoidosis and who underwent bronchoscopy with bronchoalveolar lavage (BAL), lung-draining lymph node (LLN) biopsy by EBUS-TBNA and peripheral blood (PB) sampling were included in the study. They were monitored at the Regional Referral Centre of Siena University Hospital and the Respiratory Diseases Unit of Perugia Hospital. Multicolour flow cytometry analysis through FASCLyric was performed to assess T, B and NK cell subsets. Thirty-two patients (median age (IQR) 57 (52-58) years) were consecutively and prospectively enrolled. Machine learning analysis created a model which selected CD56dim16bright, CD8, Tfc, Th17, Th12, Tfh17, Tfh2, TcemRA, ThemRA, T naïve, Tc naïve, Breg, CD1d+CD5+, Th-reg, Tfh, Th1 and CD4 cells with an accuracy of 0.9500 (kappa 0.8750). Comparative analysis found 18 cell populations that differed significantly between the three anatomical compartments. The bloodstream was enriched in ThemRA (p = 0.0416), Tfh2 (p = 0.0189), Tfh17 (p = 0.0257), Th2 (p = 0.0212), Th17 (p = 0.0177), Th-naïve (p = 0.0368), CD56dimCD16bright (p < 0.0001), CD8 (p = 0.0319), TcemRA (p < 0.0001) and Tfc cells (p = 0.0004) compared with the alveolar compartment, while Th-reg were lower in PB than BAL (p = 0.0329). The alveolar compartment was enriched in Breg (p = 0.0249) and CD1d+CD5+ (p = 0.0013) with respect to LLN samples and PB. Conversely, Tfh (p = 0.0470), Th1 (p = 0.0322), CD4 (p = 0.0486) and Tc-naïve (p = 0.0009) were more abundant in LLN than in BAL and PB. It has been speculated that changes in the relative contents of PB cells could be related to changes in production and to the selective redistribution of PB cells to granulomatous foci. This study further supports the fact that sarcoidosis is multisystemic in nature. However, the low level of immune cells in peripheral blood of patients with sarcoidosis is concerning. A re-expression of CD45RA on CD4+ and CD8+ cells could result in a reduction in peripheral immune activity. Thus, changes in the spectrum of the bloodstream may reflect both pathogenic and compensatory processes.

Differential diagnosis of pulmonary sarcoidosis: a review

Diagnosing pulmonary sarcoidosis raises challenges due to both the absence of a specific diagnostic criterion and the varied presentations capable of mimicking many other conditions. The aim of this review is to help non-sarcoidosis experts establish optimal differential-diagnosis strategies tailored to each situation. Alternative granulomatous diseases that must be ruled out include infections (notably tuberculosis, nontuberculous mycobacterial infections, and histoplasmosis), chronic beryllium disease, hypersensitivity pneumonitis, granulomatous talcosis, drug-induced granulomatosis (notably due to TNF-a antagonists, immune checkpoint inhibitors, targeted therapies, and interferons), immune deficiencies, genetic disorders (Blau syndrome), Crohn's disease, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis, and malignancy-associated granulomatosis. Ruling out lymphoproliferative disorders may also be very challenging before obtaining typical biopsy specimen. The first step is an assessment of epidemiological factors, notably the incidence of sarcoidosis and of alternative diagnoses; exposure to risk factors (e.g., infectious, occupational, and environmental agents); and exposure to drugs taken for therapeutic or recreational purposes. The clinical history, physical examination and, above all, chest computed tomography indicate which differential diagnoses are most likely, thereby guiding the choice of subsequent investigations (e.g., microbiological investigations, lymphocyte proliferation tests with metals, autoantibody assays, and genetic tests). The goal is to rule out all diagnoses other than sarcoidosis that are consistent with the clinical situation. Chest computed tomography findings, from common to rare and from typical to atypical, are described for sarcoidosis and the alternatives. The pathology of granulomas and associated lesions is discussed and diagnostically helpful stains specified. In some patients, the definite diagnosis may require the continuous gathering of information during follow-up. Diseases that often closely mimic sarcoidosis include chronic beryllium disease and drug-induced granulomatosis. Tuberculosis rarely resembles sarcoidosis but is a leading differential diagnosis in regions of high tuberculosis endemicity.

Sarcoidosis and Airway Disease After Immune Checkpoint Inhibitor Therapy: Case Study and Review of the Literature

Pulmonary toxicity from immune checkpoint inhibitor therapy is typically a severe and potentially fatal complication, but these observations are driven by the most common toxicity, pneumonitis. Rarer pulmonary immune related adverse events, like airway disease and sarcoidosis, may have a more benign course. In this case report, we present a patient in whom therapy with the PD-1 inhibitor pembrolizumab resulted in severe eosinophilic asthma and sarcoidosis. This is the first case showing that anti-IL-5 inhibition may be safe in patients who develop eosinophilic asthma after ICI therapy. We further show that sarcoidosis does not necessarily require treatment cessation. This case highlights relevant nuances when clinicians face pulmonary toxicities other than pneumonitis.

T peripheral helper cells in autoimmune diseases: What do we know?

The interactions between T cells and B cells are essential for antibody responses and the development of autoimmune diseases. Recently, a distinct subset of T cells capable of helping B cells was established in synovial fluid, and they were termed peripheral helper T (Tph) cells. PD-1hiCXCR5−CD4+ Tph cells express high levels of CXCL13, which drives the formation of lymphoid aggregates and tertiary lymphoid structures, ultimately facilitating the local production of pathogenic autoantibodies. Tph and T follicular helper cells share some key features but can be distinguished by their surface markers, transcriptional regulation, and migration capability. We summarize recent findings on Tph cells in this review and provide a perspective on their potential roles in a range of autoimmune diseases. More clinical and in-depth mechanistic investigations of Tph cells may help to improve the understanding of pathogenesis and further provide novel therapeutic targets in autoimmune diseases.

Functional link between sarcoidosis-associated gene variants and quantitative levels of bronchoalveolar lavage fluid cell types

Background

Sarcoidosis is an inflammatory disease that affects multiple organs. Cell analysis from bronchoalveolar lavage fluid (BALF) is a valuable tool in the diagnostic workup and differential diagnosis of sarcoidosis. Besides the expansion of lymphocyte expression-specific receptor segments (Vα2.3 and Vβ22) in some patients with certain HLA types, the relation between sarcoidosis susceptibility and BAL cell populations' quantitative levels is not well-understood.

Methods

Quantitative levels defined by cell concentrations of BAL cells and CD4⁺/CD8⁺ ratio were evaluated together with genetic variants associated with sarcoidosis in 692 patients with extensive clinical data. Genetic variants associated with clinical phenotypes, Löfgren's syndrome (LS) and non-Löfgren's syndrome (non-LS), were examined separately. An association test via linear regression using an additive model adjusted for sex, age, and correlated cell type was applied. To infer the biological function of genetic associations, enrichment analysis of expression quantitative trait (eQTLs) across publicly available eQTL databases was conducted.

Results

Multiple genetic variants associated with sarcoidosis were significantly associated with quantitative levels of BAL cells. Specifically, LS genetic variants, mainly from the HLA locus, were associated with quantitative levels of BAL macrophages, lymphocytes, CD3⁺ cells, CD4⁺ cells, CD8⁺ cells, CD4⁺/CD8⁺ ratio, neutrophils, basophils, and eosinophils. Non-LS genetic variants were associated with quantitative levels of BAL macrophages, CD8⁺ cells, basophils, and eosinophils. eQTL enrichment revealed an influence of sarcoidosis-associated SNPs and regulation of gene expression in the lung, blood, and immune cells.

Conclusion

Genetic variants associated with sarcoidosis are likely to modulate quantitative levels of BAL cell types and may regulate gene expression in immune cell populations. Thus, the role of sarcoidosis-associated gene-variants may be to influence cellular phenotypes underlying the disease immunopathology.

PD1, CTLA4 and TIGIT Expression on T and NK Cells in Granulomatous Diseases: Sarcoidosis and ANCA-Associated Vasculitis

Sarcoidosis is a granulomatous diseases affecting the lungs. Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a histologically granulomatous B-mediated disorder characterized by activated T cells. The expression of immune checkpoint (IC) molecules (PD1, CTLA4, TIGIT) on T- and NK-cells negatively regulate the T-cell immune function. The present study aimed to explore the peripheral distribution of IC molecules to better elucidate their peripheral tolerance failure, which might reflect the development of diseases. Patients referred to Respiratory Diseases and Rheumatology Unit of Siena University Hospital were prospectively and consecutively enrolled. Healthy subjects were also enrolled as a control group. Multicolor flow cytometric analysis was performed to detect IC molecules in the peripheral blood of patients. Twenty-three patients were consecutively and prospectively enrolled in the study: 11 patients had an AAV diagnosis and 12 had sarcoidosis. CD4⁺PD1⁺ cells were higher in sarcoidosis and GPA than in HC (p = 0.0250 and p = 0.0253, respectively). CD56⁺CTLA4⁺ were higher in sarcoidosis than GPA, MPA and HC (p = 0.0085, p = 0.0042 and p = 0.0004, respectively). CTLA4⁺NK cells clustered for 100% of sarcoidosis patients according to decision tree analysis, while PD1⁺CD4 and CD8 cells for clustered for 100% of GPA patients. Our analyses showed substantial differences between sarcoidosis and AAV, further confirming the immunological peculiarity of this disease. Despite these advances, the pathogenesis remains incompletely understood, indicating an urgent need for further research to reveal the distinct immunological events in this process, with the hope to open up new therapeutic avenues and, if possible, to develop preventive measures.

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.

Heterogeneity, subsets, and plasticity of T follicular helper cells in allergy

Antibody responses are critical for protection against pathogens. However, diseases such as allergic rhinitis or food allergy result from aberrant production of IgE antibodies against otherwise innocuous environmental antigens. The production of allergen-specific IgE requires interaction between B cells and CD4⁺ T cells, and a granular understanding of these interactions is required to develop novel therapies for allergic disease. CD4⁺ T cells are exceptionally heterogeneous in their transcriptional, epigenetic, and proteomic profiles, which poses significant challenges when attempting to define subsets relevant to the study of allergy among a continuum of cells. Defining subsets such as the T follicular helper (T_FH) cell cluster provides a shorthand to understand the functions of CD4⁺ T cells in antibody production and supports mechanistic experimentation for hypothesis-driven discovery. With a focus on allergic disease, this Rostrum article broadly discusses heterogeneity among CD4⁺ T cells and provides a rationale for subdividing T_FH cells into both functional and cytokine-skewed subsets. Further, it highlights the plasticity demonstrated by T_FH cells during the primary response and after recall, and it explores the possibility of harnessing this plasticity to reprogram immunity for therapeutic benefit in allergic disease.

The Evolving Landscape of Cutaneous Sarcoidosis: Pathogenic Insight, Clinical Challenges, and New Frontiers in Therapy

Sarcoidosis is a multisystem disorder of unknown etiology characterized by accumulation of granulomas in affected tissue. Cutaneous manifestations are among the most common extrapulmonary manifestations in sarcoidosis and can lead to disfiguring disease requiring chronic therapy. In many patients, skin disease may be the first recognized manifestation of sarcoidosis, necessitating a thorough evaluation for systemic involvement. Although the precise etiology of sarcoidosis and the pathogenic mechanisms leading to granuloma formation, persistence, or resolution remain unclear, recent research has led to significant advances in our understanding of this disease. This article reviews recent advances in epidemiology, sarcoidosis clinical assessment with a focus on the dermatologist's role, disease pathogenesis, and new therapies in use and under investigation for cutaneous and systemic sarcoidosis.

T Cell/B Cell Interactions in the Establishment of Protective Immunity

Follicular helper T cells (Tfh) are the T cell subset providing help to B cells for the generation of high-affinity antibodies and are therefore of key interest for the development of vaccination strategies against infectious diseases. In this review, we will discuss how the generation of Tfh cells and their interaction with B cells in secondary lymphoid organs can be optimized for therapeutic purposes. We will summarize different T cell subsets including Tfh-like peripheral helper T cells (Tph) capable of providing B cell help. In particular, we will highlight the novel concept of T cell/B cell interaction in non-lymphoid tissues as an important element for the generation of protective antibodies directly at the site of pathogen invasion.