Evasion of COPD in smokers: at what price?

Investigations toward the understanding of chronic obstructive pulmonary disease (COPD) have been directed, so far, to the study of mechanisms leading to the disease. We believe that understanding why ~80% of smokers evade COPD and how this evasion is accomplished might be a fruitful endeavour that could advance knowledge of the development of the disease. Since the inflammatory infiltrate smokers develop seems to be the key element leading to the lung destruction in COPD, the understanding of the possible ways inflammation can be dampened, as well as its consequences, ought to be important. We review here some of the mechanisms by which inflammation is controlled: by the post-translational regulons, by the mechanisms preventing full activation of dendritic cells and by the regulatory T-cells. The potential role of the M2 alveolar macrophage phenotype and the newly described myeloid-derived suppressor cells is mentioned. We also point out that evasion comes at a price, as healthy smokers might be immunosuppressed to some extent and unable to prevent the development of cancer, certainly less so than in severe COPD, where immunity is heightened. Probably, the knowledge of the mechanisms of evasion from COPD could add significantly to the understanding of those leading to the disease.