long-term treatment instituted, without any objective diagnostic measurements ever being made. Is there any other chronic disease for which objective diagnostic tests are readily available of which this can be said? Although the Commissioners differed in their views on the strength of evidence for diagnosis and management guided by biomarkers, particularly in children, there was a consensus that the incorporation of biomarkers into the diagnosis could only enhance the capacity to diagnose asthma responsive to ICS and lead to a paradigm shift from the current approach to diagnose the umbrella term asthma, to the diagnosis of asthma phenotypes that respond to specific treatments. New drug development Until recently we have not seen the developments in new drug discovery enjoyed by other specialty areas (table 2) 19. This area perhaps exposes the limitations of our current view of 'asthma' and airway disease most obviously. New asthma treatments are largely variants on the old; a browner inhaler, with more potent topical effects, despite increasing concerns about topical immunosuppression 103. When new treatments become available, they are widely prescribed to all comers despite being largely ineffective (Sodium Cromoglycate, Ketotifen) or effective only in subgroups of patients (Omalizumab, Mepolizumab). There has been, until recently, no concept of targeted treatment. Progress in new drug discovery has been slow, with relatively few molecules progressing from the laboratory to the clinic and a depressingly high rate of failure at the later stages of clinical development (table 2) 19. Mepolizumab, a humanised monoclonal antibody that was developed to inhibit eosinophilic airway inflammation by blocking interleukin (IL)-5, is a good example. Mepolizumab was found to be safe and effective at blocking IL-5 and reducing eosinophilic airway inflammation when tested with in vitro systems and in vivo models 104,105. A subsequent clinical trial was designed based around incorporating Mepolizumab into a step-up guideline-based paradigm 106. Within this paradigm, Mepolizumab was investigated in patients who remained symptomatic on current ICS therapy and the clinical trial focused on lung function and asthma symptoms as traditional outcome measures. Despite adequate power, this trial was unexpectedly negative. This led to much soul-searching and the near-abandonment of the drug 107. Investigators who were experienced with non-invasive measures of airway inflammation identified two important problems with this initial clinical trial: first, the heterogeneity of airway inflammation in severe asthma meant that a significant number of the trial participants would not have had eosinophilic airway inflammation and therefore would not be expected to respond; and second, the

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A complex and multilayered immune defence system protects the host against harmful agents and maintains tissue homeostasis. Cigarette smoke exposure markedly impacts the immune system, compromising the host's ability to mount appropriate immune and inflammatory responses and contributing to smoking-related pathologies. These adverse effects on the immune system not only occur in active smokers, but also in those exposed to smoke passively in contaminated environments, and may persist for decades after exposure has ended.

The protection of cells in the upper intestine against digestion by pancreatic trypsin depends on the prostanoid prostaglandin E2 (PGE2) and is mediated by protease-activated receptors in the epithelium. As the airway epithelium is morphologically similar and also expresses one of these receptors, PAR2, and is a major source of PGE2, we reasoned that bronchial epithelial PAR2 might also participate in prostanoid-dependent cytoprotection in the airways. Here we show that activation of PAR2, which co-localizes immunohistochemically with trypsin(ogen) in airway epithelium, causes the relaxation of airway preparations from mouse, rat, guinea-pig and humans by the release of a cyclooxygenase product from the epithelium. This physiological protective response in isolated airways also occurred in anaesthetized rats, where activation of PAR2 caused a marked and prolonged inhibition of bronchoconstriction. After desensitization of PAR2, the response to trypsin recovered rapidly by mechanisms dependent on de novo synthesis and trafficking of proteins. Our results indicate that trypsin released from the epithelium can initiate powerful bronchoprotection in the airways by activation of epithelial PAR2.

The clinical response to influenza infection ranges from mild disease to severe pneumonia and it remains unclear whether the inflammatory response to infection is protective or pathogenic. We have defined a novel role for neutrophils in ameliorating lung injury during influenza infection, thereby limiting development of severe disease. Infection of neutrophil-depleted mice with influenza virus HKx31 (H3N2) led to rapid weight loss, pneumonia, and death. Neutropenia was associated with enhanced virus replication in the respiratory tract; however, viral titers were declining at the time of death, leading us to investigate other factors contributing to mortality. In addition to thymic atrophy, lymphopenia, and viremic spread, depletion of neutrophils led to exacerbated pulmonary inflammation, edema, and respiratory dysfunction. Thus, while it is well established that neutrophils contribute to lung injury in a range of pathological conditions, reduced numbers or impaired neutrophil function can facilitate progression of mild influenza to severe clinical disease.

Aerosol antigen challenge of ovalbumin-sensitized mice induced an eosinophilic airway inflammation that was dependent on interleukin (IL)-5 and CD4+, but not CD8+, T lymphocytes. The involvement of the Th2 phenotype of CD4+ T cells was supported by demonstrating that FACS-sorted purified lung T cells from sensitized, but not control, mice produced IL-4, IL-5, and IL-10 after activation of the CD3/TCR complex. To determine the role of IL-4 in this process, we used mice in which the gene for IL-4 was deleted by homologous recombination. Antigen challenge of IL-4 gene-targeted mice resulted in a marked attenuation of eosinophilic inflammation and IL-5 secretion. To more fully understand the time when IL-4 was involved, we administered a neutralizing anti-IL-4 antibody (11B11) either immediately before antigen challenge or during immunization. Inhibition of IL-4 before antigen challenge had little effect on antigen-induced eosinophil infiltration. However, when 11B11 was administered during immunization, there was a marked reduction in eosinophil infiltration. Cross-linking of the CD3/TCR complex of FACS-sorted lung T cells revealed that only when anti-IL-4 was administered during immunization was there an inhibition of T cell-derived IL-5 and IgE production. These results suggest that IL-4 is central both to the induction of a local Th2 response and to the development of eosinophilic inflammation of the lung. Moreover, we suggest a sequential involvement of IL-4 and IL-5, with IL-4 committing naive T cells to a Th2 phenotype which upon activation by aerosol provocation secrete IL-5, resulting in eosinophil accumulation.

Cigarette smoke exposure is a major determinant of adverse lung health, but the molecular processes underlying its effects on inflammation and immunity remain poorly understood. Therefore, we sought to understand whether inflammatory and host defense determinants are affected during subchronic cigarette smoke exposure. Dose-response and time course studies of lungs from Balb/c mice exposed to smoke generated from 3, 6, and 9 cigarettes/day for 4 days showed macrophage- and S100A8-positive neutrophil-rich inflammation in lung tissue and bronchoalveolar lavage (BAL) fluid, matrix metalloproteinase (MMP) and serine protease induction, sustained NF-kappaB translocation and binding, and mucus cell induction but very small numbers of CD3+CD4+ and CD3+CD8+ lymphocytes. Cigarette smoke had no effect on phospho-Akt but caused a small upregulation of phospho-Erk1/2. Activator protein-1 and phospho-p38 MAPK could not be detected. Quantitative real-time PCR showed upregulation of chemokines (macrophage inflammatory protein-2, monocyte chemoattractant protein-1), inflammatory mediators (TNF-alpha, IL-1beta), leukocyte growth and survival factors [granulocyte-macrophage colony-stimulating factor, colony-stimulating factor (CSF)-1, CSF-1 receptor], transforming growth factor-beta, matrix-degrading MMP-9 and MMP-12, and Toll-like receptor (TLR)2, broadly mirroring NF-kappaB activation. No upregulation was observed for MMP-2, urokinase-type plasminogen activator, tissue-type plasminogen activator, and TLRs 3, 4, and 9. In mouse strain comparisons the rank order of susceptibility was Balb/c > C3H/HeJ > 129SvJ > C57BL6. Partition of responses into BAL macrophages vs. lavaged lung strongly implicated macrophages in the inflammatory responses. Strikingly, except for IL-10 and MMP-12, macrophage and lung gene profiles in Balb/c and C57BL/6 mice were very similar. The response pattern we observed suggests that subchronic cigarette smoke exposure may be useful to understand pathogenic mechanisms triggered by cigarette smoke in the lungs including inflammation and alteration of host defense.

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