Airway neutrophils and interleukin-17

It is well known that exacerbations of obstructive airways disease such as asthma and chronic obstructive pulmonary disease are associated with an inc reased number of neutrophils in the airways. However, the mechanisms behind this phenomenon are poorly understood. There is in vivo experimental evidence that the number of airway neutrophil is is controlled by certain T-lymphocytes, but the mediators responsible fo r this lymphocyte-related neutrophilia have not yet been identified. In this review, novel evidence that the T-lymphocyte-related cytokine inter leukin (IL)-17 can link the activation of certain T-lymphocytes to the recr uitment and activation of airway neutrophils is described. The IL-17-induce d neutrophil recruitment is mediated via induced CXC chemokine release thro ugh steroid-sensitive mechanisms and is modulated by release of endogenous tachykinins. These effects of IL-17 are potentiated by other pro-inflammato ry cytokines such as (IL-1 beta) and tumour necrosis factor-alpha. Clinical studies are needed to evaluate whether or not targeting these mech anisms can provide a useful pharmacotherapeutical approach against exaggera ted mobilization of neutrophils in obstructive airways disease.