We aimed to characterise lymphoid neogenesis in bronchiectasis and cystic fibrosis (CF) lungs and to examine the role of bacterial infection.Lymphoid aggregates were examined using immunohistochemical staining and morphometric analysis in surgical lung sections obtained from nonsmokers and patients with bronchiectasis or CF. Sterile, - or-coated agarose beads were instilled intratracheally in mice. Kinetics of lymphoid neogenesis and chemokine expression were examined over 14 days.Lymphoid aggregates were scarce in human lungs of nonsmokers, but numerous peribronchial lymphoid aggregates containing B-lymphocytes, T-lymphocytes, germinal centres and high endothelial venules were found in bronchiectasis and CF. Mouse lungs contained no lymphoid aggregate at baseline. During persistent or airway infection peribronchial lymphoid neogenesis occurred. At day 14 after instillation, lymphoid aggregates expressed markers of tertiary lymphoid organs and the chemokines CXCL12 and CXCL13. The airway epithelium was an important site of CXCL12, CXCL13 and interleukin-17A expression, which began at day 1 after instillation.Peribronchial tertiary lymphoid organs are present in bronchiectasis and in CF, and persistent bacterial infection triggered peribronchial lymphoid neogenesis in mice. Peribronchial localisation of tertiary lymphoid organs and epithelial expression of chemokines suggest roles for airway epithelium in lymphoid neogenesis.

Background In cystic fibrosis (CF), recurrent infections suggest impaired mucosal immunity but whether production of secretory immunoglobulin A (S-IgA) is impaired remains elusive. S-IgA is generated following polymeric immunoglobulin receptor (pIgR)-mediated transepithelial transport of dimeric (d-)IgA and represents a major defence through neutralisation of inhaled pathogens like Pseudomonas aeruginosa ( Pa ). Methods Human lung tissue (n = 74), human sputum (n = 118), primary human bronchial epithelial cells (HBEC) (cultured in air-liquid interface) (n = 19) and mouse lung tissue and bronchoalveolar lavage were studied for pIgR expression, IgA secretion and regulation. Findings Increased epithelial pIgR immunostaining was observed in CF lung explants, associated with more IgA-producing plasma cells, sputum and serum IgA, especially Pa -specific IgA. In contrast, pIgR and IgA transport were downregulated in F508del mice, CFTR-inhibited HBEC, and CF HBEC. Moreover, the unfolded protein response (UPR) due to F508del mutation, inhibited IgA transport in Calu-3 cells. Conversely, pIgR expression and IgA secretion were strongly upregulated following Pa lung infection in control and F508del mice, through an inflammatory host response involving interleukin-17. Interpretation A complex regulation of IgA secretion occurs in the CF lung, UPR induced by CFTR mutation/dysfunction inhibiting d-IgA transcytosis, and Pa infection unexpectedly unleashing this secretory defence mechanism. Funding This work was supported by the Forton's grant of the King Baudouin's Foundation, Belgium, the Fondazione Ricerca Fibrosi Cistica, Italy, and the Fonds National de la Recherche Scientifique, Belgium.

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The incidence of pulmonary embolism (PE) is high during severe Coronavirus Disease 2019 (COVID-19). We aimed to identify predictive and prognostic factors of PE in non-ICU hospitalized COVID-19 patients. In the retrospective multicenter observational CLOTVID cohort, we enrolled patients with confirmed RT-PCR COVID-19 who were hospitalized in a medicine ward and also underwent a CT pulmonary angiography for a PE suspicion. Baseline data, laboratory biomarkers, treatments, and outcomes were collected. Predictive and prognostics factors of PE were identified by using logistic multivariate and by Cox regression models, respectively. A total of 174 patients were enrolled, among whom 86 (median [IQR] age of 66 years [55–77]) had post-admission PE suspicion, with 30/86 (34.9%) PE being confirmed. PE occurrence was independently associated with the lack of long-term anticoagulation or thromboprophylaxis (OR [95%CI], 72.3 [3.6–4384.8]) D-dimers ≥ 2000 ng/mL (26.3 [4.1–537.8]) and neutrophils ≥ 7.0 G/L (5.8 [1.4–29.5]). The presence of these two biomarkers was associated with a higher risk of PE (p = 0.0002) and death or ICU transfer (HR [95%CI], 12.9 [2.5–67.8], p < 0.01). In hospitalized non-ICU severe COVID-19 patients with clinical PE suspicion, the lack of anticoagulation, D-dimers ≥ 2000 ng/mL, neutrophils ≥ 7.0 G/L, and these two biomarkers combined might be useful predictive markers of PE and prognosis, respectively.

Background A high prevalence of pulmonary embolism (PE) has been described during COVID‐19. Our aim was to identify predictive factors of PE in non‐ICU hospitalized COVID‐19 patients. Methods Data and outcomes were collected upon admission during a French multicenter retrospective study, including patients hospitalized for COVID‐19, with a CT pulmonary angiography (CTPA) performed in the emergency department for suspected PE. Predictive factors significantly associated with PE were identified through a multivariate regression model. Results A total of 88 patients (median [IQR] age of 68 years [60‐78]) were analyzed. Based on CTPA, 47 (53.4%) patients were diagnosed with PE, and 41 were not. D‐dimer ≥3000 ng/mL (OR 8.2 [95% CI] 1.3‐74.2, sensitivity (Se) 0.84, specificity (Sp) 0.78, P = .03), white blood count (WBC) ≥12.0 G/L (29.5 [2.3‐1221.2], Se 0.47, Sp 0.92, P = .02), and ferritin ≥480 µg/L (17.0 [1.7‐553.3], Se 0.96, Sp 0.44, P = .03) were independently associated with the PE diagnosis. The presence of the double criterion D‐dimer ≥3000 ng/mL and WBC ≥12.0 G/L was greatly associated with PE (OR 21.4 [4.0‐397.9], P = .004). Conclusion The white blood count, the D‐dimer and ferritin levels could be used as an indication for CTPA to confirm PE on admission in non‐ICU COVID‐19 patients.

BackgroundTertiary lymphoid structures (TLS) are triggered by persistent bronchopulmonary infection with S. aureus but their roles remain elusive. The present study sought to examine the effects of B and/or T cell depletion on S. aureus infection and TLS development (lymphoid neogenesis) in mice.MethodsC57Bl/6 mice were pretreated with (1) an anti-CD20 mAb (B cell depletion) or (2) an anti-CD4 and/or an anti-CD8 mAbs (T cell depletion) or (3) a combination of anti-CD20, anti-CD4 and anti-CD8 mAbs (combined B and T cell depletion) or (4) with isotype control mAbs. After lymphocyte depletion, mice were infected by intratracheal instillation of agarose beads containing S. aureus (106 CFU/mouse). Fourteen days later, bacterial load and lung inflammatory cell infiltration were assessed by cultures and immunohistochemistry, respectively.ResultsFourteen days after S. aureus-bead instillation, lung bacterial load was comparable between control and lymphocyte-depleted mice. While TLS were observed in the lungs of infected mice pretreated with control mAbs, these structures were disorganised or abolished in the lungs of lymphocyte-depleted mice. The absence of CD20+ B lymphocytes had no effect on CD3+ T lymphocyte infiltration, whereas CD4+/CD8+ T-cell depletion markedly reduced CD20+ B cell infiltration. Depletion of CD4+ or CD8+ T cells separately had limited effect on B cell infiltration but lead to the absence of germinal center.ConclusionTLS disorganisation is not associated with loss of infection control in mice persistently infected with S. aureus.