Tertiary lymphoid structures and B-cell infiltration are IPF features with functional consequences.

Background: Recent literature has shown the presence of B cells and autoantibodies in idiopathic pulmonary fibrosis (IPF) which would imply the presence of tertiary lymphoid structures (TLS, sites where the immune response is triggered), yet TLS are not considered features of the histological characteristics of IPF. Aim: This study aims to quantify the presence, size, and degree of activation of TLS in biopsied and explanted lungs from patients with early- and late-IPF, never treated with antifibrotics, and relate their presence and activity to the clinical course, disease progression, and lung inflammation. Methods: Immunohistochestry for B cells and CD4, CD8, and CD45 cells was performed in lung tissue from IPF patients: 18 at diagnosis (early), 39 explanted (end-stage), and 12 smoking controls. TLS activation was assessed by CD40 expression. Spirometry along 31 (12-72) months of follow-up was used to characterize end-stage IPF as slow progressors or rapid progressors. Results: B cells, along with other inflammatory cells, were higher in early- and end-stage IPF than in controls (p < 0.001). In rapid progressors, all inflammatory cells were higher than in slow progressors (p < 0.05). TLS were present in 100% of early- and end-stage IPF and in 50% of controls. In end-stage IPF, the TLS area and activation score were higher than in early IPF (p < 0.0001; p = 0.005) and controls (p < 0.04; p < 0.002). TLS activation score correlated with FVC decline during follow-up in rapid progressors (r = 0.73; p = 0.007) but not in slow progressors. Conclusions: A prominent B-cell infiltration, along with the presence of TLS, the activity of which correlates with FVC decline, is an important component of IPF from the beginning of the disease, likely playing an important role on its mechanism and progression.

Unveiling the Cutting-Edge Impact of Polarized Macrophage-Derived Extracellular Vesicles and MiRNA Signatures on TGF-ß Regulation within Lung Fibroblasts.

Depending on local cues, macrophages can polarize into classically activated (M1) or alternatively activated (M2) phenotypes. This study investigates the impact of polarized macrophage-derived Extracellular Vesicles (EVs) (M1 and M2) and their cargo of miRNA-19a-3p and miRNA-425-5p on TGF-ß production in lung fibroblasts. EVs were isolated from supernatants of M0, M1, and M2 macrophages and quantified using nanoscale flow cytometry prior to fibroblast stimulation. The concentration of TGF-ß in fibroblast supernatants was measured using ELISA assays. The expression levels of miRNA-19a-3p and miRNA-425-5p were assessed via TaqMan-qPCR. TGF-ß production after stimulation with M0-derived EVs and with M1-derived EVs increased significantly compared to untreated fibroblasts. miRNA-425-5p, but not miRNA-19a-3p, was significantly upregulated in M2-derived EVs compared to M0- and M1-derived EVs. This study demonstrates that EVs derived from both M0 and M1 polarized macrophages induce the production of TGF-ß in fibroblasts, with potential regulation by miRNA-425-5p.

Suppressor of cytokine signaling-3 expression and its regulation in relation to inflammation in Chronic Obstructive Pulmonary Disease.

Background: The family of Suppressor of Cytokine Signaling (SOCS) acts as a controller of the duration and intensity of cytokine function by negatively regulating the JAK-STAT signaling pathway. SOCS' role in inflammatory diseases in animal models is well demonstrated. However, its role in the development of human disease is still under investigation. SOCS3 plays an important role in tumor development where its downregulation has been implicated in the pathogenesis of various solid tumors such as triple-negative breast cancer. Aim: The aim of this work was to study (1) the expression of SOCS3 in smokers' lungs and its relation to the degree of inflammation and (2) SOCS3 regulation by microRNA (miRNA) in alveolar-macrophage (AM)-derived extracellular vesicles (EVs) in bronchoalveolar lavage (BAL). Methods: Group A: 35 smokers' [19 with COPD (SC) and 16 without COPD (S)] and 9 nonsmokers (NS); SOCS3, TNFα in AM, and CD8+ T cells were quantified by immunohistochemistry, in lung tissue. Group B: additional 9 SC, 11 S, and 5 NS; AM-EVs expressing SOCS3 (CD14+SOCS3+) and SOCS3 suppressors miRNA-19a-3p and 221-3p in EVs were quantified by flow cytometry and PCR, in BAL. Results: The percentage of SOCS3+ AM was higher in SC [68 (6.6-99)%] and S [48 (8-100)%] than in NS [9.6 (1.9-61)%; p = 0.002; p = 0.03] and correlated with % of TNFα+AM (r = 0.48; p = 0.0009) and CD8+ T cells (r = 0.44; p = 0.0029). In BAL, the CD14+SOCS3+ EVs/µL were increased in SC [33 (21-74)] compared to S [16 (8-37); p = 0.03] and NS [9 (7-21); p = 0.003]. Conversely, miRNA-19a-3p and miRNA-221-3p expression were increased in S when compared to SC [19 (2-53) vs. 3 (0.6-8); p = 0.03 and 3 (0.005-9.6) vs. 0.2 (0.08-0.7); p = 0.05]. Conclusions: The suppressor function of SOCS3 in COPD seems to be overridden by other factors and does not follow the animal-model paradigm. Expression of SOCS3 in BAL macrophage-derived EVs might be useful to assess the degree of inflammation and possible progression of COPD. Downregulation of SOCS3, by miRNA, in smokers without COPD might contribute to the risk of developing cancer in these patients.

Clinical Applications of Endobronchial Ultrasound (EBUS) Scope: Challenges and Opportunities.

Endobronchial Ultrasound (EBUS) has been widely used to stage lung tumors and to diagnose mediastinal diseases. In the last decade, this procedure has evolved in several technical aspects, with new tools available to optimize tissue sampling and to increase its diagnostic yield, like elastography, different types of needles and, most recently, miniforceps and cryobiopsy. Accordingly, the indications for the use of the EBUS scope into the airways to perform the Endobronchial Ultrasound-TransBronchial Needle Aspiration (EBUS-TBNA) has also extended beyond the endobronchial and thoracic boundaries to sample lesions from the liver, left adrenal gland and retroperitoneal lymph nodes via the gastroesophageal tract, performing the Endoscopic UltraSound with Bronchoscope-guided Fine Needle Aspiration (EUS-B-FNA). In this review, we summarize and critically discuss the main indication for the use of the EBUS scope, even the more uncommon, to underline its utility and versatility in clinical practice.

Macrophages-derived Factor XIII links coagulation to inflammation in COPD.

Background: The local, extravascular, activation of the coagulation system in response to injury is a key factor mediating the resulting inflammatory response. Coagulation Factor XIIIA (FXIIIA) found in alveolar macrophages (AM) and dendritic cells (DC), by influencing fibrin stability, might be an inflammatory modifier in COPD. Aims: To study the expression of FXIIIA in AM and Langerin+DC (DC-1) and their relation to the inflammatory response and disease progression in COPD. Methods: In 47 surgical lungs, 36 from smokers (22 COPD and 14 no-COPD) and 11 from non-smokers we quantified by immunohistochemistry FXIIIA expression in AM and DC-1 along with numbers of CD8+Tcells and CXCR3 expression in lung parenchyma and airways. Lung function was measured prior to surgery. Results: The percentage of AM expressing FXIII (%FXIII+AM) was higher in COPD than no-COPD and non-smokers. DC-1 expressed FXIIIA and their numbers were higher in COPD than no-COPD and non-smokers. DC-1 positively correlated with %FXIII+AM (r=0.43; p<0.018). CD8+Tcells, which were higher in COPD than in no-COPD, were correlated with DC-1 (p<0.01) and %FXIII+AM. CXCR3+ cells were increased in COPD and correlated with %FXIII+AM (p<0.05). Both %FXIII+AM (r=-0.6; p=0.001) and DC-1 (r=-0.7; p=0.001) correlated inversely with FEV1. Conclusion: FXIIIA, an important link between the extravascular coagulation cascade and inflammatory response, is significantly expressed in alveolar macrophages and dendritic cells of smokers with COPD, suggesting that it could play an important role in the adaptive inflammatory reaction characteristic of the disease.

Extracellular Vesicles (EVs) as Crucial Mediators of Cell-Cell Interaction in Asthma.

Asthma is the most common chronic respiratory disorder worldwide and accounts for a huge health and economic burden. Its incidence is rapidly increasing but, in parallel, novel personalized approaches have emerged. Indeed, the improved knowledge of cells and molecules mediating asthma pathogenesis has led to the development of targeted therapies that significantly increased our ability to treat asthma patients, especially in severe stages of disease. In such complex scenarios, extracellular vesicles (EVs i.e., anucleated particles transporting nucleic acids, cytokines, and lipids) have gained the spotlight, being considered key sensors and mediators of the mechanisms controlling cell-to-cell interplay. We will herein first revise the existing evidence, mainly by mechanistic studies in vitro and in animal models, that EV content and release is strongly influenced by the specific triggers of asthma. Current studies indicate that EVs are released by potentially all cell subtypes in the asthmatic airways, particularly by bronchial epithelial cells (with different cargoes in the apical and basolateral side) and inflammatory cells. Such studies largely suggest a pro-inflammatory and pro-remodelling role of EVs, whereas a minority of reports indicate protective effects, particularly by mesenchymal cells. The co-existence of several confounding factors-including technical pitfalls and host and environmental confounders-is still a major challenge in human studies. Technical standardization in isolating EVs from different body fluids and careful selection of patients will provide the basis for obtaining reliable results and extend their application as effective biomarkers in asthma.

Extracellular Vesicles in Lung Cancer: Bystanders or Main Characters?

Lung cancer still represents the main cause of cancer death worldwide. The poor survival is mainly related to the diagnosis which is often obtained in advanced stages when the disease is unresectable and characterized by the worst prognosis. Only in the last decades have great discoveries led to the development of new therapies targeted to oncogenes and to boost the host immune response against the tumor. Tumor identification and molecular/immunological characterization rely on bioptic samples which represent the gold standard for diagnosis. Nonetheless, less invasive procedures providing small samples will be more and more common in the future. Extracellular vesicles (EV), submicron particles released by any cell type, are candidates for diagnostic and prognostic biomarkers. EV are mediators of intercellular communication and can convey cytokines, miRNAs, antigens, and many other factors of tumorigenesis. This review summarizes the most appealing findings on lung-cancer-related EV, debating the evidence on circulating versus airway EV as potential biomarkers in disease management and the main studies on the role of these particles on lung cancer pathogenesis. Overall, the available results point toward a wide range of possible applications, supported by the promising achievements of genotyping on BAL fluid EV and proteomic analysis on pleural effusion EV. Nonetheless, the study of lung EV is still affected by remarkable methodological issues, especially when in vitro evidence is translated into humans. Whether EV still represent an "information fog" or can be useful in lung cancer management will be discussed, with possible hints on how to improve their usage.

Chronic Bronchitis Affects Outcomes in Smokers without Chronic Obstructive Pulmonary Disease (COPD).

BACKGROUND: Chronic bronchitis (CB) importantly affects outcomes in smokers with COPD, but the effects on smokers without COPD are less well known and less emphasized. The aim of our study was to investigate the possible effects of CB on clinical outcomes in smokers without COPD (noCOPD) and compare them with the effects in smokers with COPD (COPD). METHODS: For that purpose, we studied 511 smokers, 302 with and 209 without COPD, followed for 10 years in an academic COPD ambulatory setting. Chronic bronchitis was defined as the presence of cough and sputum production for at least 3 months in each of two consecutive years. All subjects underwent clinical and functional examination with spirometry, diffusion capacity (DLco), 6-min walking test (6MWT), mMRC Dyspnoea Scale, COPD Assessment Test (CAT), and recording of annual frequency of exacerbations. All-cause mortality during follow-up was recorded. RESULTS: 27% of noCOPD and 45% of COPD had CB. noCOPD with CB had lower FEV1 and DLco, worse 6MWT, more dyspnoea, a higher number of exacerbations and lower survival than noCOPD without CB. CB did not affect FEV1 decline in noCOPD but it significantly did in COPD. CONCLUSIONS: The presence of chronic bronchitis in smokers without COPD will significantly affect symptoms, quality of life, and survival, underlining the importance of recognizing the condition and managing it accordingly.

Symptomatic smokers without COPD have physiological changes heralding the development of COPD.

Background: COPD is a major health problem, mainly due to cigarette smoking. Most studies in COPD are dedicated to fully developed COPD in older subjects, even though development of COPD may start soon after smoking initiation. Therefore, there is a need to diagnose this "early disease" by detecting the initial events responsible for ultimate development of COPD. Methods: Measurement of maximum mid expiratory flow between 25 and 75% of vital capacity (MMEF) in a routine spirometry, which detects small airways disease, was used to investigate if MMEF abnormalities in smokers without COPD (noCOPD) would relate to respiratory symptoms and identify smokers that might progress to COPD. For this purpose we studied 511 smokers, 302 COPD and 209 noCOPD, followed long term with spirometry including MMEF, diffusing capacity of the lung for carbon monoxide (D LCO), 6-min walk test (6MWT), Medical Research Council Dyspnoea Scale and COPD Assessment Test. Three spirometries V1,V2 and V3 (5±2.5 and 10±4 years apart from V1) were performed to assess functional decline and development of COPD. Results: 65% of noCOPD had an abnormal MMEF (<80%) and 38% an abnormal D LCO. The NoCOPD with MMEF <80% group performed worse in the 6MWT (p=0.01), was more dyspnoeic (p=0.01) and had higher prevalence of chronic bronchitis than the noCOPD with MMEF>80% group (p=0.04). 21% of noCOPD with MMEF <80% and 2.7% with MMEF>80% developed COPD by V3 (p=0.0004). Conclusions: The MMEF, a functional test available in a routine spirometry, can detect early lung abnormalities and identify the subset of symptomatic smokers with pathological changes that might lead to COPD.

Risk Factors for Development and Severity of COVID-19 in COPD Patients.

The impact that COVID-19 could have on patients with COPD is a real concern. In this study we evaluated, in a cohort of longitudinally followed COPD subjects, the incidence of COVID-19, seeking for possible risk factors and prognostic factors predicting the clinical outcome. In our cohort of 370 patients (followed for 5.3 ± 2.7 years), 22 developed COVID-19 (COPD/COVID-19+) between February/November 2020 (5.9%). Cardio-metabolic conditions (hypertension, dyslipidemia, obesity, diabetes) but not respiratory abnormalities (FEV1, DLCO, emphysema and exacerbation history), were risk factors for development of COVID-19 in COPD patients. Out of the 22 COPD/COVID-19+ patients, 10 needed intensive care. Low DLCO and emphysema, but also metabolic comorbidities, were related to the need for intensive care.

Critical Review of the Evolution of Extracellular Vesicles' Knowledge: From 1946 to Today.

Extracellular vesicles (EVs) are a family of particles/vesicles present in blood and body fluids, composed of phospholipid bilayers that carry a variety of molecules that can mediate cell communication, modulating crucial cell processes such as homeostasis, induction/dampening of inflammation, and promotion of repair. Their existence, initially suspected in 1946 and confirmed in 1967, spurred a sharp increase in the number of scientific publications. Paradoxically, the increasing interest for EV content and function progressively reduced the relevance for a precise nomenclature in classifying EVs, therefore leading to a confusing scientific production. The aim of this review was to analyze the evolution of the progress in the knowledge and definition of EVs over the years, with an overview of the methodologies used for the identification of the vesicles, their cell of origin, and the detection of their cargo. The MISEV 2018 guidelines for the proper recognition nomenclature and ways to study EVs are summarized. The review finishes with a "more questions than answers" chapter, in which some of the problems we still face to fully understand the EV function and potential as a diagnostic and therapeutic tool are analyzed.

Low-Blood Lymphocyte Number and Lymphocyte Decline as Key Factors in COPD Outcomes: A Longitudinal Cohort Study.

BACKGROUND: Smokers with and without chronic obstructive pulmonary disease (COPD) are at risk of severe outcomes like exacerbations, cancer, respiratory failure, and decreased survival. The mechanisms for these outcomes are unclear; however, there is evidence that blood lymphocytes (BL) number might play a role. OBJECTIVE: The objective of this study is to investigate the relationship between BL and their possible decline over time with long-term outcomes in smokers with and without COPD. METHODS: In 511 smokers, 302 with COPD (COPD) and 209 without COPD (noCOPD), followed long term, we investigated whether BL number and BL decline over time might be associated with long-term outcomes. Smokers were divided according to BL number in high-BL (≥1,800 cells/µL) and low-BL (<1,800 cells/µL). Clinical features, cancer incidence, and mortality were recorded during follow-up. BL count in multiple samples and BL decline over time were calculated and related to outcomes. RESULTS: BL count was lower in COPD (1,880 cells/µL) than noCOPD (2,300 cells/µL; p < 0.001). 43% of COPD and 23% of noCOPD had low-BL count (p < 0.001). BL decline over time was higher in COPD than noCOPD (p = 0.040). 22.5% of the whole cohort developed cancer which incidence was higher in low-BL subjects and in BL decliners than high-BL (31 vs. 18%; p = 0.001) and no decliners (32 vs. 19%; p = 0.002). 26% in the cohort died during follow-up. Furthermore, low-BL count, BL decline, and age were independent risk factors for mortality by Cox regression analysis. CONCLUSION: BL count and BL decline are related to worse outcomes in smokers with and without COPD, which suggests that BL count and decline might play a mechanistic role in outcomes deterioration. Insights into mechanisms inducing the fall in BL count could improve the understanding of COPD pathogenesis and point toward new therapeutic measures.

Heart Failure is Highly Prevalent and Difficult to Diagnose in Severe Exacerbations of COPD Presenting to the Emergency Department.

BACKGROUND: Some 20% of patients with stable Chronic Obstructive Pulmonary Disease (COPD) might have heart failure (HF). HF contribution to acute exacerbations of COPD (AECOPD) presenting to the emergency department (ED) is not well established. AIMS: To assess (1) the HF incidence in patients presenting to the ED with AECOPD; (2) the concordance between ED and respiratory ward (RW) diagnosis; (3) the factors associated with risk of death after hospital discharge. METHODS: Retrospective chart review of 119 COPD patients presenting to ED for acute exacerbation of respiratory symptoms and then admitted to RW where a final diagnosis of AECOPD, AECOPD and HF and AECOPD and OD (other diagnosis), was obtained. ED and RW diagnosis were then compared. Factors affecting survival at follow-up were investigated. RESULTS: At RW, 40.3% of cases were diagnosed of AECOPD, 40.3% of AECOPD and HF and 19.4% of AECOPD and OD, with ED diagnosis coinciding with RW's in 67%, 23%, and 57% of cases respectively. At RW, 60% of patients in GOLD1 had HF, of which 43% were diagnosed at ED, while 40% in GOLD4 had HF that was never diagnosed at ED. Lack of inclusion in a COPD care program, HF, and early readmission for AECOPD were associated with mortality. CONCLUSIONS: HF is highly prevalent and difficult to diagnose in patients in all GOLD stages presenting to the ED with severe AECOPD, and along with lack of inclusion in a COPD care program, confers a high risk for mortality.

High-Resolution CT Change over Time in Patients with Idiopathic Pulmonary Fibrosis on Antifibrotic Treatment.

Antifibrotic treatment slows down functional decline and disease progression in idiopathic pulmonary fibrosis (IPF). High-resolution computed tomography (HRCT) is useful to diagnose IPF; however, little is known about whether and to what extent HRCT changes reflect functional changes during antifibrotic therapy. The aim of this study was, therefore, to assess HRCT change over time after 1 year of treatment and to evaluate whether these changes correlate with functional decline over the same period of time. Sixty-eight IPF patients on antifibrotic treatment (i.e., pirfenidone or nintedanib) were functionally categorized as stable or progressors based on whether (or not) they had a decline in forced vital capacity (FVC) >5% predicted/year, and their HRCT were scored blindly and independently by two expert thoracic radiologists at treatment initiation (HRCT1) and after 1 year of treatment (HRCT2). Ground glass opacities (Alveolar Score, AS), reticulations (Interstitial Score, IS) and honeycombing (HC) were quantified and correlated with FVC decline between HRCT1 and HRCT2. At treatment initiation, HRCT scores were similar in both stable patients and progressors. After one year of treatment, in the entire population, AS and HC increased significantly, while IS did not. However, when stratified by the rate of functional decline, in stable patients, HC increased significantly while AS and IS did not. On the other hand, among progressors AS and HC increased significantly whereas IS did not. In the entire population, the combined score of fibrosis (IS + HC) correlated significantly with FVC decline. In conclusion, IPF patients on antifibrotic treatment exhibit different patterns of HRCT change over time based on their rate of functional decline. HRCT data should be integrated to lung function data when assessing response to antifibrotic treatment in patients with IPF.

Exome Sequencing Reveals Immune Genes as Susceptibility Modifiers in Individuals with α1-Antitrypsin Deficiency.

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder associated to early onset emphysema, mainly imputable to Pi*ZZ genotype. In spite of the serious potential effects, many AATD individuals do not develop emphysema. To identify genes/variants potentially involved in emphysema development we studied 4 AATD families. Each family had at least one affected sibling with emphysema and one non-affected. Whole Exome Sequencing (WES) was performed on genomic DNA isolated from 9 individuals with AATD (4 affected/5 non-affected). Genetic variants confirmed at least in three families were prioritized using QueryOR and network analysis was used to verify enriched pathways. In affected subjects: 14 genes (57% immune-related) segregated in a recessive model and 21 (29% immune-related) in a dominant model. In non-affected subjects: 21 genes (43% immune-related) segregated in a recessive model and 50 (24% immune-related) in a dominant model. In affected siblings immune genes had an activating function, while where immune-suppressing in non-affected siblings involving antigen processing, MHC-I presentation, TCR and PD-1 signalling. This study describes possible genetic susceptibility factors for emphysema development in AATD, and suggests that gene variants involved in regulation of immune homeostasis and maintenance of self-tolerance contribute to the development or suppression of the disease.

Reassessing the Role of Eosinophils as a Biomarker in Chronic Obstructive Pulmonary Disease.

Blood eosinophils measurement, as proxy for tissue eosinophils, has become an important biomarker for exacerbation risk and response to inhaled corticosteroids (ICS) in Chronic Obstructive Pulmonary Disease (COPD). Its use to determine the pharmacological approach is recommended in the latest COPD guidelines. The potential role of blood eosinophils is mainly based on data derived from post-hoc and retrospective analyses that showed an association between increased blood eosinophils and risk of exacerbations, as well as mitigation of this risk with ICS. Yet other publications, including studies in real life COPD, do not confirm these assumptions. Moreover, anti-eosinophil therapy targeting interleukin (IL)-5 failed to reduce exacerbations in COPD patients with high blood eosinophils, which casts significant doubts on the role of eosinophils in COPD. Furthermore, a reduction of eosinophils might be harmful since COPD patients with relatively high eosinophils have better pulmonary function, better life quality, less infections and longer survival. These effects are probably linked to the role of eosinophils in the immune response against pathogens. In conclusion, in COPD, high blood eosinophils are widely used as a biomarker for exacerbation risk and response to ICS. However, much is yet to be learned about the reasons for the high eosinophil counts, their variations and their controversial effects on the fate of COPD patients.

High-Resolution Computed Tomography (HRCT) Reflects Disease Progression in Patients with Idiopathic Pulmonary Fibrosis (IPF): Relationship with Lung Pathology.

High-Resolution Computed Tomography (HRCT) plays a central role in diagnosing Idiopathic Pulmonary Fibrosis (IPF) while its role in monitoring disease progression is not clearly defined. Given the variable clinical course of the disease, we evaluated whether HRCT abnormalities predict disease behavior and correlate with functional decline in untreated IPF patients. Forty-nine patients (with HRCT1) were functionally categorized as rapid or slow progressors. Twenty-one had a second HRCT2. Thirteen patients underwent lung transplantation and pathology was quantified. HRCT Alveolar (AS) and Interstitial Scores (IS) were assessed and correlated with Forced Vital Capacity (FVC) decline between HRCT1 and HRCT2. At baseline, AS was greater in rapids than in slows, while IS was similar in the two groups. In the 21 subjects with HRCT2, IS increased over time in both slows and rapids, while AS increased only in rapids. The IS change from HRCT1 to HRCT2 normalized per month correlated with FVC decline/month in the whole population, but the change in AS did not. In the 13 patients with pathology, the number of total lymphocytes was higher in rapids than in slows and correlated with AS. Quantitative estimation of HRCTs AS and IS reflects the distinct clinical and pathological behavior of slow and rapid decliners. Furthermore, AS, which reflects the immune/inflammatory infiltrate in lung tissue, could be a useful tool to differentiate rapid from slow progressors at presentation.

α1-Antitrypsin Polymerizes in Alveolar Macrophages of Smokers With and Without α1-Antitrypsin Deficiency.

BACKGROUND: The deficiency of α1-antitrypsin (AAT) is secondary to misfolding and polymerization of the abnormal Z-AAT in liver cells and is associated with lung emphysema. Alveolar macrophages (AMs) produce AAT; however, it is not known whether Z-AAT can polymerize in AMs, further decreasing lung AAT and promoting lung inflammation. Our intention was to investigate whether AAT polymerizes in human AMs and to study the possible relation between polymerization and degree of lung inflammation. METHODS: Immunohistochemical analysis with 2C1 monoclonal antibody specific for polymerized AAT was performed in sections of the following: nine lungs from individuals with AAT deficiency (AATD) and severe COPD; 35 smokers with normal AAT levels, of whom 24 had severe COPD and 11 did not have COPD; and 13 nonsmokers. AMs positive for AAT polymers were counted and expressed as the percentage of total AMs in the lungs. RESULTS: AAT polymerization was detected in 27% (4%-67%) of AMs from individuals with AATD but also in AMs from smokers with normal AAT with (24% [0%-70%]) and without (24% [0%-60%]) COPD, but not in AMs from nonsmokers (0% [0%-1.5%]) (P < .0001). The percentage of AMs with polymerized AAT correlated with pack-years smoked (r = 0.53, P = .0001), FEV1/FVC (r = -0.41, P = .005), small airways disease (r = 0.44, P = .004), and number of CD8+ T cells and neutrophils in alveolar walls (r = 0.51, P = .002; r = 0.31, P = .05, respectively). CONCLUSIONS: Polymerization of AAT in alveolar macrophages occurs in the lungs of individuals with AATD but also in smokers with normal AAT levels with or without COPD. Our findings highlight the similarities in the pathophysiology of COPD in individuals with and without AATD, adding a potentially important step to the mechanism of COPD.