Bronchus-associated macrophages efficiently capture and present soluble inhaled antigens and are capable of local Th2 cell activation
- University of California, San Francisco, United States
Abstract
In allergic asthma, allergen inhalation leads to local Th2 cell activation and peribronchial inflammation. However, the mechanisms for local antigen capture and presentation remain unclear. By two-photon microscopy of the mouse lung, we established that soluble antigens in the bronchial airway lumen were efficiently captured and presented by a population of CD11c+ interstitial macrophages with high CX3CR1-GFP and MHC class II expression. We refer to these cells as Bronchus-Associated Macrophages (BAMs) based on their localization underneath the bronchial epithelium. BAMs were enriched in collagen-rich regions near some airway branchpoints, where inhaled antigens are likely to deposit. BAMs engaged in extended interactions with effector Th2 cells and promoted Th2 cytokine production. BAMs were also often in contact with dendritic cells (DCs). After exposure to inflammatory stimuli, DCs migrated to draining lymph nodes, whereas BAMs remained lung resident. We propose that BAMs act as local antigen presenting cells in the lung and also transfer antigen to DCs.
Data availability
Relevant data are included in the manuscript figures and examples of 3D visualizations and time-lapse imaging are provided as videos. The RNAseq data have been deposited at the NCBI Gene Expression Omnibus (GEO) and are accessible through GEO Series accession number GSE214177 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE214177)
Article and author information
Author details
Christopher D C Allen
Funding
National Heart, Lung, and Blood Institute (DP2HL117752)
- Xin-Zi Tang
- Cynthia Cho
- Christopher D C Allen
National Institute of Allergy and Infectious Diseases (R21AI130495)
- Xin-Zi Tang
- Cynthia Cho
- Christopher D C Allen
UCSF Cardiovascular Research Institute
- Xin-Zi Tang
- Lieselotte S M Kreuk
- Cynthia Cho
- Christopher D C Allen
UCSF Sandler Asthma Basic Research Center
- Xin-Zi Tang
- Lieselotte S M Kreuk
- Cynthia Cho
- Christopher D C Allen
Agency for Science, Technology and Research
- Xin-Zi Tang
National Institute of Allergy and Infectious Diseases (T32AI007334-31)
- Lieselotte S M Kreuk
UCSF Program for Breakthrough Biomedical Research
- Ross Metzger
- Christopher D C Allen
National Heart, Lung, and Blood Institute (T32HL007731-28)
- Lieselotte S M Kreuk
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Florent Ginhoux, Agency for Science Technology and Research, Singapore
Ethics
Animal experimentation: The care, maintenance, and experimental manipulation of mice followedguidelines established by the Institutional Animal Care and Use Committee of the University of California, San Francisco under approved protocols AN079036, AN089524, AN111286, AN175836, and AN191685.
Version history
- Preprint posted: September 19, 2020 (view preprint)
- Received: September 21, 2020
- Accepted: August 10, 2022
- Accepted Manuscript published: September 29, 2022 (version 1)
- Version of Record published: October 12, 2022 (version 2)
Copyright
© 2022, Tang et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Bronchus-associated macrophages efficiently capture and present soluble inhaled antigens and are capable of local Th2 cell activation
eLife 11:e63296.
https://doi.org/10.7554/eLife.63296
Further reading
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- Immunology and Inflammation
- Medicine
Background:
Prinflammatory extracellular chromatin from neutrophil extracellular traps (NETs) and other cellular sources is found in COVID-19 patients and may promote pathology. We determined whether pulmonary administration of the endonuclease dornase alfa reduced systemic inflammation by clearing extracellular chromatin.
Methods:
Eligible patients were randomized (3:1) to the best available care including dexamethasone (R-BAC) or to BAC with twice-daily nebulized dornase alfa (R-BAC + DA) for seven days or until discharge. A 2:1 ratio of matched contemporary controls (CC-BAC) provided additional comparators. The primary endpoint was the improvement in C-reactive protein (CRP) over time, analyzed using a repeated-measures mixed model, adjusted for baseline factors.
Results:
We recruited 39 evaluable participants: 30 randomized to dornase alfa (R-BAC +DA), 9 randomized to BAC (R-BAC), and included 60 CC-BAC participants. Dornase alfa was well tolerated and reduced CRP by 33% compared to the combined BAC groups (T-BAC). Least squares (LS) mean post-dexamethasone CRP fell from 101.9 mg/L to 23.23 mg/L in R-BAC +DA participants versus a 99.5 mg/L to 34.82 mg/L reduction in the T-BAC group at 7 days; p=0.01. The anti-inflammatory effect of dornase alfa was further confirmed with subgroup and sensitivity analyses on randomised participants only, mitigating potential biases associated with the use of CC-BAC participants. Dornase alfa increased live discharge rates by 63% (HR 1.63, 95% CI 1.01–2.61, p=0.03), increased lymphocyte counts (LS mean: 1.08 vs 0.87, p=0.02) and reduced circulating cf-DNA and the coagulopathy marker D-dimer (LS mean: 570.78 vs 1656.96 μg/mL, p=0.004).
Conclusions:
Dornase alfa reduces pathogenic inflammation in COVID-19 pneumonia, demonstrating the benefit of cost-effective therapies that target extracellular chromatin.
Funding:
LifeArc, Breathing Matters, The Francis Crick Institute (CRUK, Medical Research Council, Wellcome Trust).
Clinical trial number:
-
- Immunology and Inflammation
Trained immunity is the long-term functional reprogramming of innate immune cells, which results in altered responses toward a secondary challenge. Despite indoxyl sulfate (IS) being a potent stimulus associated with chronic kidney disease (CKD)-related inflammation, its impact on trained immunity has not been explored. Here, we demonstrate that IS induces trained immunity in monocytes via epigenetic and metabolic reprogramming, resulting in augmented cytokine production. Mechanistically, the aryl hydrocarbon receptor (AhR) contributes to IS-trained immunity by enhancing the expression of arachidonic acid (AA) metabolism-related genes such as arachidonate 5-lipoxygenase (ALOX5) and ALOX5 activating protein (ALOX5AP). Inhibition of AhR during IS training suppresses the induction of IS-trained immunity. Monocytes from end-stage renal disease (ESRD) patients have increased ALOX5 expression and after 6 days training, they exhibit enhanced TNF-α and IL-6 production to lipopolysaccharide (LPS). Furthermore, healthy control-derived monocytes trained with uremic sera from ESRD patients exhibit increased production of TNF-α and IL-6. Consistently, IS-trained mice and their splenic myeloid cells had increased production of TNF-α after in vivo and ex vivo LPS stimulation compared to that of control mice. These results provide insight into the role of IS in the induction of trained immunity, which is critical during inflammatory immune responses in CKD patients.
