Mucosal immune alterations at the early onset of tissue destruction in chronic obstructive pulmonary disease

Rationale

COPD is characterized by chronic airway inflammation, small airways changes, with disappearance and obstruction, and also distal/alveolar destruction (emphysema). The chronology by which these three features evolve with altered mucosal immunity remains elusive. This study assessed the mucosal immune defense in human control and end-stage COPD lungs, by detailed microCT and RNA transcriptomic analysis of diversely affected zones.

Methods

In 11 control (non-used donors) and 11 COPD (end-stage) explant frozen lungs, 4 cylinders/cores were processed per lung for microCT and tissue transcriptomics. MicroCT was used to quantify tissue percentage and alveolar surface density to classify the COPD cores in mild, moderate and severe alveolar destruction groups, as well as to quantify terminal bronchioles in each group. Transcriptomics of each core assessed fold changes in innate and adaptive cells and pathway enrichment score between control and COPD cores. Immunostainings of immune cells were performed for validation.

Results

In mildly affected zones, decreased defensins and increased mucus production were observed, along CD8+ T cell accumulation and activation of the IgA pathway. In more severely affected zones, CD68+ myeloid antigen-presenting cells, CD4+ T cells and B cells, as well as MHCII and IgA pathway genes were upregulated. In contrast, terminal bronchioles were decreased in all COPD cores.

Conclusion

Spatial investigation of end-stage COPD lungs show that mucosal defense dysregulation with decreased defensins and increased mucus and IgA responses, start concomitantly with CD8+ T-cell accumulation in mild emphysema zones, where terminal bronchioles are already decreased. In contrast, adaptive Th and B cell activation is observed in areas with more advanced tissue destruction. This study suggests that in COPD innate immune alterations occur early in the tissue destruction process, which affects both the alveoli and the terminal bronchioles, before the onset of an adaptive immune response.

High-resolution computed tomography in assessment of patients with emphysema

OBJECTIVE

To assess whether high-resolution computed tomography (HRCT) variables are as good as other known clinical variables in grading emphysema patients.

METHODS

A detailed clinical history was taken and physical examination performed. We performed serum study, lung function testing, and HRCT scanning to assess emphysema. Mean lung density, the attenuation value separating the least 15% of pixels (PERC15), the percentage of the relative area of the lungs with attenuation values < -950 Hounsfield units (HU) (RA950), and histogram analysis were calculated from computerized data.

RESULTS

The final analysis was based on data from 92 subjects, and they were moderately emphysematous (mean lung density was -877 ± 23 HU, PERC15 was -953 ± 21 HU, and RA950 was 16 ± 5%). There was a significant difference regarding subjective emphysema severity in the St George's Respiratory Questionnaire, smoking history, FEV1, C-reactive protein, age, and body mass index (P < .001). There was a significant correlation between the 3 objective image variables and the 6 objective clinical variables (St George's Respiratory Questionnaire, smoking history, FEV1, C-reactive protein, age, and body mass index) (P < .001).

CONCLUSIONS

This study shows the possible important role of HRCT in the diagnosis and quantification of pulmonary emphysema.