Small airway inflammation in asthma

Asthma was originally described as an inflammatory disease that predominantly involves the central airways. Pathological and physiological evidence reported during the past few years suggests that the inflammatory process extends beyond the central airways to the peripheral airways and the lung parenchyma. The small airways are capable of producing T-helper-2 cytokines, as well as chemokines, and they have recently been recognized as a predominant site of airflow obstruction in asthmatic persons. The inflammation at this distal site has been described as more severe than large airway inflammation. These findings are of great clinical significance, and highlight the need to consider the peripheral airways as a target in any therapeutic strategy for treatment of asthma.

The influence of infections on the development and severity of allergic disorders

The frequency and severity of atopic disorders are steadily increasing, particularly in developing countries. The reason for this observation is not clear. Recent studies indicate that infections with viruses and especially with bacteria early in life may help to inhibit allergic Th2 responses by skewing the immune system towards Th1 responses. However, infections can also lead to the exacerbation of atopic disorders.