Immunological Similarities and Differences between Post-COVID-19 Lung Sequelae and Idiopathic Pulmonary Fibrosis.

INTRODUCTION: Pulmonary fibrosis is an irreversible condition that may be caused by known (including viral triggers such as SARS-CoV-2) and unknown insults. The latter group includes idiopathic pulmonary fibrosis (IPF), which is a chronic, progressive fibrosing interstitial pneumonia of unknown cause. The longer the insult acts on lung tissue, the lower the probability of a complete resolution of the damage. An emerging clinical entity post-COVID-19 is pulmonary fibrosis (PCPF), which shares many pathological, clinical, and immunological features with IPF. The fibrotic response in both diseases-IPF and PCPF-is orchestrated in part by the immune system. An important role regarding the inhibitory or stimulatory effects on immune responses is exerted by the immune checkpoints (ICs). The aim of the present study was to analyse the similarities and differences between CD4+, CD8+, and NK cells in the peripheral blood of patients affected by fibrotic disease, IPF, and PCPF compared with sarcoidosis patients and healthy controls. The second aim was to evaluate the expression and co-expression of PD-1 and TIGIT on CD4, CD8, and NK cells from our patient cohort. METHODS: One hundred and fifteen patients affected by IPF, PCPF, and sarcoidosis at the rare pulmonary disease centre of the University of Siena were enrolled. Forty-eight patients had an IPF diagnosis, 55 had PCPF, and 12 had sarcoidosis. Further, ten healthy controls were enrolled. PCPF patients were included between 6 and 9 months following hospital discharge for COVID-19. The peripheral blood samples were collected, and through flow cytometric analysis, we analysed the expression of CD4, CD8, NK cells, PD-1, and TIGIT. RESULTS: The results show a greater depletion of CD4 and NK cells in IPF patients compared to other groups (p = 0.003), in contrast with CD8 cells (p < 001). Correlation analysis demonstrated an indirect correlation between CD4 and CD8 cells in IPF and sarcoidosis patients (p < 0.001 = -0.87 and p = 0.042; r = -0.6, respectively). Conversely, PCPF patients revealed a direct correlation between CD4 and CD8 cells (p < 0.001; r = 0.90) accentuating an immune response restoration. The expression of PD-1 and TIGIT was abundant on T and NK cell subsets of the two lung fibrotic groups, IPF and PCPF. Analogously, the co-expression of PD-1 and TIGIT on the surfaces of CD4 and CD8 were increased in such diseases. Conclusions: Our study shines a spotlight on the immune responses involved in the development of pulmonary fibrosis, idiopathic and secondary to SARS-CoV-2 infection. We observed a significant imbalance not only in CD4, CD8, and NK blood percentages in IPF and PCPF patients but also in their functional phenotypes evaluated through the expression of ICs.

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.

Immunological Pathways in Sarcoidosis and Autoimmune Rheumatic Disorders-Similarities and Differences in an Italian Prospective Real-Life Preliminary Study.

BACKGROUND: The pathogenesis of sarcoidosis involves T cells and B lymphocytes that produce autoantibodies. We compared the expression of different T and B cell subsets in sarcoidosis and three B-mediated rheumatic diseases that can affect the lungs in an attempt to identify similarities and differences that distinguish these diseases. METHODS: The study included patients referred to Siena University Hospital's respiratory disease and rheumatology units. Patients were enrolled prospectively and consecutively. Healthy volunteers were also included. Multicolor flow cytometry was performed on phenotype T and B cell subsets. Multivariate analysis was carried out to reduce the dimensionality of the data. RESULTS: Fifteen patients had a diagnosis of sarcoidosis, fourteen idiopathic inflammatory myopathies (IIM), five granulomatosis with polyangiitis (GPA), ten microscopic polyangiitis (MPA), and seven were controls. Thirty-five T and B cell subsets were phenotyped, 15 of which were significantly different in sarcoidosis, B-mediated rheumatic disorders, and controls. Principal components analysis distinguished the four groups of patients with a total explained variance of 54.7%. A decision tree was constructed to determine which clustering variables would be most useful for distinguishing sarcoidosis, IIM, MPA, and GPA. The model showed regulatory T helper cells (Th-reg) > 5.70% in 91% of sarcoidosis patients as well as Th-reg ≤ 5.70 and Th17 > 43.27 in 100% of MPA. It also showed Th-reg ≤ 5.70, Th17 ≤ 43.27 and Tfh-reg ≥ 7.81 in 100% of GPA patients, and Th-reg ≤ 5.70, Th17 ≤ 43.27 and Tfh-reg ≤ 7.81 in 100% of IIM patients. CONCLUSION: The immune cell profile sheds light on similarities and differences between sarcoidosis and B-mediated rheumatic diseases. Sarcoidosis and autoimmune diseases show similar patterns of cellular immune dysregulation, suggesting a common pathogenic pathway that may provide an opportunity for further understanding autoimmunity and exploring biological therapies to treat sarcoidosis.

The Effects of Interstitial Lung Diseases on Alveolar Extracellular Vesicles Profile: A Multicenter Study.

Diagnosis of interstitial lung diseases (ILD) is difficult to perform. Extracellular vesicles (EVs) facilitate cell-to-cell communication, and they are released by a variety of cells. Our goal aimed to investigate EV markers in bronchoalveolar lavage (BAL) from idiopathic pulmonary fibrosis (IPF), sarcoidosis and hypersensitivity pneumonitis (HP) cohorts. ILD patients followed at Siena, Barcelona and Foggia University Hospitals were enrolled. BAL supernatants were used to isolate the EVs. They were characterized by flow cytometry assay through MACSPlex Exsome KIT. The majority of alveolar EV markers were related to the fibrotic damage. CD56, CD105, CD142, CD31 and CD49e were exclusively expressed by alveolar samples from IPF patients, while HP showed only CD86 and CD24. Some EV markers were common between HP and sarcoidosis (CD11c, CD1c, CD209, CD4, CD40, CD44, CD8). Principal component analysis distinguished the three groups based on EV markers with total variance of 60.08%. This study has demonstrated the validity of the flow cytometric method to phenotype and characterize EV surface markers in BAL samples. The two granulomatous diseases, sarcoidosis and HP, cohorts shared alveolar EV markers not revealed in IPF patients. Our findings demonstrated the viability of the alveolar compartment allowing identification of lung-specific markers for IPF and HP.

Immune-Checkpoint Expression on CD4, CD8 and NK Cells in Blood, Bronchoalveolar Lavage and Lymph Nodes of Sarcoidosis.

BACKGROUND: Sarcoidosis features non-necrotizing granulomas consisting mainly of activated CD4-lymphocytes. T-cell activation is regulated by immune checkpoint (IC) molecules. The present study aimed to compare IC expression on CD4, CD8 and NK cells from peripheral, alveolar and lung-draining lymph node (LLN) samples of sarcoidosis patients. METHODS: Flow-cytometry analysis was performed to detect IC molecules and a regression decision tree model was constructed to investigate potential binary classifiers for sarcoidosis diagnosis as well as for the IC distribution. RESULTS: Fourteen patients (7 females) were consecutively recruited in the study; all enrolled patients showed hilo-mediastinal lymph node enlargement and lung parenchyma involvement with chest X-rays and high resolution computed tomography. CD4+PD1+ and CD8+PD1+ were higher in bronchoalveolar lavage (BAL) than in LLN (p = 0.0159 and p = 0.0439, respectively). CD4+ T-cell immunoglobulin and ITIM domain (TIGIT)+ were higher in BAL than in peripheral blood mononuclear cells (PBMCs) (p = 0.0239), while CD8+TIGIT+ were higher in PBMC than in BAL (p = 0.0386). CD56+TIGIT+ were higher in LLN than in PBMC (p = 0.0126). The decision-tree model showed the best clustering cells of PBMC, BAL and LLN: CD56, CD4/CD8 and CD4+TIGIT+ cells. Considering patients and controls, the best subset was CD4+CTLA-4+. CONCLUSION: High expression of PD1 and TIGIT on T cells in BAL, as well as CTLA-4 and TIGIT on T cells in LLN, suggest that inhibition of these molecules could be a therapeutic strategy for avoiding the development of chronic inflammation and tissue damage in sarcoidosis patients.

CD103 Expression on Regulatory and Follicular T Cells in Lymph Nodes, Bronchoalveolar Lavage Fluid and Peripheral Blood of Sarcoidosis Patients.

(1) Background: Sarcoidosis is a chronic multisystem disorder of unknown aetiology, driven by a T-cell mechanism allowing T-cell attachment and transmigration through the endothelium, and endorsed by the expression of an integrin alpha-E beta-7 (CD103). This study aimed to analyse the different distribution and compartmentalisation of CD103 expression on T cell subsets in BAL, peripheral blood mononuclear cells (PBMC) and lymph nodes (LLN) from sarcoidosis patients. (2) Patients: We consecutively and prospectively enrolled 14 sarcoidosis patients. We collected PBMC, LLN and BAL at the same time from all patients. Through flow cytometric analysis, we analysed the expression of CD103 on regulatory and follicular T cell subsets. (3) Results: All patients were in radiological Scadding stage II. The multivariate analysis found that the variables which most influenced the peripheral blood compartment were high CD8+ and low ThReg, CD8+CD103+ and Tfh cell percentages. A principal component analysis plot performed to distinguish LLN, BAL and PBMC showed that they separated on the basis of CD4+, CD4+CD103+, CD8+, CD8+CD103+, TcEffector, TcNaive, ThNaive, ThEffector, Threg, ThregCD103+, Tfh, TcfCXC5+ and CD4+CD103+/CD4+ with 65.96% of the total variance. (4) Conclusions: Our study is the first to report a link between the imbalance in circulating, alveolar and lymph node CD8+ and CD8+CD103+ T cells, ThReg, Tfh and ThNaive and the CD103+CD4+/CD4+ T cell ratio in the development of sarcoidosis. These findings shine a spotlight on the pathogenesis of sarcoidosis and may offer new predictors for diagnosis. Our study provides additional understanding for a personalised, and hopefully more effective treatment of sarcoidosis.

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.

Adaptive immune system in pulmonary sarcoidosis-Comparison of peripheral and alveolar biomarkers.

Sarcoidosis is a multi-systemic granulomatous disease of unknown origin. Recent research has focused upon the role of autoimmunity in its development and progression. This study aimed to determine and define the disturbance and distribution of T and B cell subsets in the alveolar and peripheral compartments. Thirteen patients were selected for the study [median age, interquartile range (IQR) = 57 years (48-59); 23% were male]. Twelve healthy controls [median age, IQR = 53 years (52-65); 16% male] were also enrolled into the study. Cellular and cytokine patterns were measured using the cytofluorimetric approach. Peripheral CD8 percentages were higher in sarcoidosis patients (SP) than healthy controls (HC) (p = 0.0293), while CD4 percentages were lower (p = 0.0305). SP showed low bronchoalveolar lavage (BAL) percentages of CD19 (p = 0.0004) and CD8 (p = 0.0035), while CD19+ CD5+ CD27- percentages were higher (p = 0.0213); the same was found for CD4 (p = 0.0396), follicular regulatory T cells (Treg ) (p = 0.0078) and Treg (p < 0.0001) cells. Low T helper type 17 (Th17) percentages were observed in BAL (p = 0.0063) of SP. Peripheral CD4+ C-X-C chemokine receptor (CXCR)5+ CD45RA- ) percentages and follicular T helper cells (Tfh)-like Th1 (Tfh1) percentages (p = 0.0493 and p = 0.0305, respectively) were higher in the SP than HC. Tfh1 percentages and Tfh-like Th2 percentages were lower in BAL than in peripheral blood (p = 0.0370 and p = 0.0078, respectively), while CD4+ C-X-C motif CXCR5+ CD45RA- percentages were higher (p = 0.0011). This is the first study, to our knowledge, to demonstrate a link between an imbalance in circulating and alveolar Tfh cells, especially CCR4-, CXCR3- and CXCR5-expressing Tfh subsets in the development of sarcoidosis. These findings raise questions about the pathogenesis of sarcoidosis and may provide new directions for future clinical studies and treatment strategies.

Portable Pocket-Sized Ultrasound Scanner for the Evaluation of Lung Involvement in Coronavirus Disease 2019 Patients.

Ultrasound imaging of the lung (LUS) and associated tissues has demonstrated clinical utility in coronavirus disease 2019 (COVID-19) patients. The aim of the present study was to evaluate the possibilities of a portable pocket-sized ultrasound scanner in the evaluation of lung involvement in patients with COVID-19 pneumonia. We conducted 437 paired readings in 34 LUS evaluations of hospitalized individuals with COVID-19. The LUS scans were performed on the same day with a standard high-end ultrasound scanner (Venue GO, GE Healthcare, Chicago, IL, USA) and a pocket-sized ultrasound scanner (Butterfly iQ, Butterfly Network Inc., Guilford, CT, USA). Fourteen scans were performed on individuals with severe cases, 11 on individuals with moderate cases and nine on individuals with mild cases. No difference was observed between groups in days since onset of symptoms (23.29 ± 10.07, 22.91 ± 8.91 and 28.56 ± 11.13 d, respectively; p = 0.38). No significant differences were found between LUS scores obtained with the high-end and the portable pocket-sized ultrasound scanner. LUS scores in individuals with mild respiratory impairment were significantly lower than in those with moderate and severe cases. Our study confirms the possibilities of portable pocket-sized ultrasound imaging of the lung in COVID-19 patients. Portable pocket-sized ultrasound scanners are cheap, easy to handle and equivalent to standard scanners for non-invasive assessment of severity and dynamic observation of lung lesions in COVID-19 patients.

Predicting survival in newly diagnosed idiopathic pulmonary fibrosis: a 3-year prospective study.

The natural history of idiopathic pulmonary fibrosis (IPF) is not well defined and its clinical course is variable. We sought to investigate the survival and incidence of acute exacerbations (AEs) and their significant predictors in newly diagnosed patients. 70 patients newly diagnosed with IPF were prospectively followed for at least 3 yrs. Baseline evaluation included Medical Research Council dyspnoea score (MRCDS), 6-min walk test, pulmonary function tests, all of which were repeated at 6 months, and high-resolution computed tomography. A retrospective cohort of 68 patients was used for confirmation. Mean survival from the time of diagnosis was 30 months, with a 3-yr mortality of 46%. A Risk stratificatiOn ScorE (ROSE) based on MRCDS > 3, 6-min walking distance ≤ 72% predicted and composite physiologic index > 41 predicted 3-yr mortality with high specificity. 6-month progression of ROSE predicted rapid progression. 3-yr incidence of AE was 18.6%, mostly occurring in the first 18 months; risk factors for AE were concomitant emphysema and low diffusing coefficient of the lung for carbon monoxide. Results were confirmed in an independent cohort of patients. In newly diagnosed IPF, advanced disease at presentation, rapid progression and AEs are the determinants of 3-yr survival. The purpose of the multifactorial ROSE is to risk-stratify patients in order to predict survival and detect rapid disease progression.

The analysis of tryptase in serum of sarcoidosis patients.

Sarcoidosis is a systemic granulomatous disease of unknown etiology characterized by activation of macrophages and T lymphocytes. Relatively little is known about the role of mast cells and their mediators in the pathogenesis of sarcoidosis. Tryptase is an enzyme produced by activated mast cells, regarded as a marker of mast cell activation. To analyse tryptase concentrations in serum of sarcoidosis patients in an attempt to define the role of tryptase and mast cells in the pathogenesis of sarcoidosis and to evaluate the potential of tryptase as marker of disease severity. Quantitative analysis of tryptase concentrations was performed in serum of patients with stable sarcoidosis (n = 12), progressive sarcoidosis (n = 23) and controls (n = 13). Patients enrolled in the study had been monitored at Siena Regional Referral Centre for Sarcoidosis from onset for at least 12 months. Significantly higher concentrations of tryptase were found in peripheral blood of sarcoidosis patients (6.08 +/- 3.98 microg/l) than controls (2.96 +/- 1.75microg/l; p = 0.012). Patients with progressive disease showed the highest tryptase concentrations in serum. Tryptase and mast cells may be involved in the immunopathogenesis of sarcoidosis and further studies are required to understand if tryptase may represent a marker of sarcoidosis severity.