EDITORIAL Chlamydia pneumoniae: crossing the barriers?

Chlamydia pneumoniae has been recognised as a cause of respiratory tract infections and implicated as a potential risk factor or causative agent in different extrapulmonary diseases including atherosclerosis, multiple sclerosis, and Alzheimer9s disease [1–3]. Being an obligate intracellular bacterium, C. pneumoniae has been detected in circulating monocytes and can activate inflammatory processes in epithelial, endothelial and smooth muscle cells in vitro [4]. In the present issue of the European Respiratory Journal (ERJ), GIEFFERS et al. [5] report an animal model showing that intratracheal infection with C. pneumoniae is followed by systemic dissemination of the infection mediated by peripheral blood mononuclear cells (PBMCs). The authors, on the basis of both the animal model and in vitro study results, hypothesise a "cellular model " for C. pneumonia