Chronic obstructive pulmonary disease (COPD) is a major public health problem because: (1) it causes significant morbidity and mortality which is expected to increase worldwide in the near future;1 (2) it jeopardises the quality of life of the patients suffering from this devastating disease (particularly during exacerbations);2,3 and (3) it imposes an enormous global healthcare cost.1 However, because the pathogenesis of COPD is poorly understood, treatment is mostly symptomatic and new therapeutic strategies are limited.4 In this paper we propose a new hypothesis that considers the largely unexplored role of the immune system in the pathogenesis of COPD. If true, this hypothesis will generate new therapeutic opportunities in COPD.