Systemic inflammation and lung function

Abstract

The current view on inflammation in COPD is foremost based on examinations of luminal samples and bronchial tissues. Inflammation in peripheral lung tissues has however remained relatively unexplored. Our research characterises structural alterations of the lung immune system (i.e. “immune remodelling”) in COPD. With focus on changes in lymphoid tissues and lymphatic vessels, immune remodelling was studied in patients with different severities of COPD and compared to never-smoking and smoking control subjects. The results confirmed an expansion of bronchiolar-associated lymphoid tissue (BALT) in COPD but also revealed increased lymphoid tissues in pulmonary vessels and the alveolar parenchyma. While the lymphoid structures in COPD had a leukocyte composition similar to controls, several leukocyte populations were activated, with e.g. increased expression of CXCL13 and ETS-1. In COPD lungs, increased numbers and size of lymphatic vessels were found in bronchiolar wall, pulmonary vessel, and alveolar compartments. Lymphatic vessels also displayed increased immunoreactivity for the cell traffic regulating chemokine CCL21. Altogether, our data suggest that in COPD all major lung compartments are subjected to immune remodelling with expansion and activation of lymphoid tissues and lymphatic vessels as significant features. These observations may have implications for the abnormal cell traffic and chronic inflammation in COPD.