The role of neutrophils in inflammation

It has long been noted that inflammation underlies asthma. It is now recognized that there is marked heterogeneity in the stimuli that can cause or aggravate this inflammation, the cells that are involved in the response and the consequences in terms of both pathology and symptoms. The prime role of eosinophilic inflammation in the pathogenesis of asthma is acknowledged in this paper, but the potential role of neutrophilic inflammation to underlie symptoms and physiological changes that are characteristic of asthma is highlighted. A minority group of patients appear to have asthma from clinical signs, but their airway secretions do not contain eosinophils. Their response to treatment is unlike that of patients with typical eosinophilic airway inflammation in that they do not respond to steroid therapy. Published data from in vitro and animal work provide a conceptual framework to explain these observations. The refinement of the technique of examining sputum cellular content to assess airway inflammation provides an opportunity to identify and study this subgroup of patients.