Hyperpolarized noble gas MRI using 3He and 129Xe has allowed void space imaging of the lungs for several years. Hyperpolarized 83Kr MRI has also been shown to provide an MRI contrast sensitive to the surface-to-volume ratio and chemistry of synthetic porous systems. Ex vivo animal models of pulmonary diseases and in vitro experiments were used in this thesis to examine three methodological advances allowing for the measurement of pulmonary physiological parameters using 129Xe and 83Kr. The 83Kr quadrupolar property was explored in a rat model of pulmonary surface-to-volume ratio degradation, i.e. emphysema. The surface quadrupolar relaxation (SQUARE) of the noble gas provided maps of the longitudinal relaxation in control and emphysematous rat lungs. The relaxation observations were regionally correlated to the histological measurements of the alveolar degradation. The 129Xe solubility in the lungs, blood, and more generally liquids, was the basis for the design of a new biosensor composed of a cryptophane cage tethered to a paramagnetic agent. The depolarization of the 129Xe atoms encapsulated by the cryptophane, followed by chemical exchange with the surrounding medium was investigated in vitro. This model biosensor will lead to a future switchable biosensor that will be deactivated by the enzymatic cleavage of the encapsulating cage and the paramagnetic agent. Finally, the 129Xe solubility was further utilised to study the gas transfer through ex vivo rat lungs after blood replacement by a perfluorocarbon emulsion. The large chemical shift separating the 129Xe peaks for the gas phase, the tissue and the perfluorocarbon emulsion, allowed for a selective excitation of each phase and the independent observation of their signal build-up after inhalation. This mechanism will be used as a biomarker for gas transfer impairment in animal models of pulmonary fibrosis.

Background: The United Kingdom (UK) has poor lung cancer survival rates compared to other countries, and this is partly explained by differences in early mortality. In order to diagnose lung cancer at an earlier stage in the UK there is a pressing need to understand the management process from the recognition of symptoms by people with lung cancer, through the initial interactions with primary care to the referral to secondary care and the choice of the subsequent treatment plan. Objectives: The aim of this thesis is to use mixed methods to identify some of the factors which may affect the diagnosis and prognosis in patients with lung cancer in the United Kingdom across the whole patient pathway. Methods: Prospectively collected clinical data were used in conjunction with qualitative methodology. Primary care records were obtained from The Health Improvement Network, alongside data from the National Lung Cancer Audit (NLCA), linked to Hospital Episode Statistics and Office for National Statistics datasets. Case-control and cohort studies were conducted using multivariable logistic regression to look at independent associations with early mortality, likelihood of receiving surgery and place of death. Survival analyses were performed using Kaplan Meier curves and Cox regression and validation studies used area under the receiver operating curves (AUC). The Framework approach was used to identify themes and sub-themes arising from focus group interviews. Results: Mixed methods were used to look at barriers to early diagnosis and attitudes towards lung cancer screening in a high risk population. A number of key practical and emotional barriers which may impact on screening uptake were identified, alongside the issue of smoking stigma and blame. Primary care data were used to look at predictors of early (0-90 day) mortality in the UK. Thirty per cent of patients with lung cancer died within 90 days of diagnosis. Increasing age, male sex, socioeconomic deprivation, rural versus urban location and current smoking were all independently associated with early death. Patients who had poorer prognosis did interact with primary care before diagnosis, suggesting missed opportunities to identify them earlier. NLCA data linked to organisational audit data highlighted inequities between Trusts, in particular with regards to variability in the workload of specialists and differences in access to diagnostic and therapeutic modalities. On site access to positron emission computed tomography, stereotactic ablative radiotherapy and video-assisted thoracoscopic lobectomy were independently associated with increased likelihood of receiving surgery for lung cancer. Records for patient who developed brain metastases following radical surgical treatment for lung cancer were reviewed. Those with more advanced disease stage, younger age and adenocarcinoma sub-type were more likely to develop metastases and modelling suggested that 71% may have been visible pre-operatively had magnetic resonance imaging of the brain been performed as part of the staging process. An internal and external validation was performed to assess the ability of two risk scoring systems to predict 90 day post-operative mortality. AUC values for internal and external validation of the NLCA score and validation of Thoracoscore were 0.68 (95% CI 0.63-0.72), 0.60 (95% CI 0.56-0.65) and 0.60 (95% CI 0.54-0.66) respectively. Post-hoc analysis was performed using NLCA records on 15554 surgical patients to derive summary tables for 30 and 90 day mortality, stratified by procedure type, age and performance status. Linked NLCA data were used to look at place of death from lung cancer. Thirty-five per cent of patients with lung cancer die in acute hospital beds, with male sex, old age (≥ 85 years), socioeconomic deprivation, WHO performance status 4 at diagnosis and emergency route to diagnosis all independently associated with increased likelihood of death in this setting. There is marked geographical variation in place of death, particularly with regard to provision of hospice services. Conclusions: The studies described in this thesis use prospectively collected data to provide a snapshot of different aspects of the lung cancer patient journey which may impact on prognosis, alongside qualitative methodology to try to determine reasons for diagnostic delay and attitudes towards screening programmes. There remain some important clinical questions about lung cancer care and outcomes which need to be looked at to provide a greater understanding of where the inequities in the lung cancer patient pathway in the UK lie and to try to address modifiable factors with an aim to improve outcomes.

Clinicians use several oxygen-based indices in intensive care units as surrogates to determine the condition of the patient’s lung and verify monitoring progress. Examples of these oxygen indices include the ratio of arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2 ratio); arterial/alveolar oxygen tension ratio (PaO2/PAO2); alveolar–arterial oxygen tension difference (PA-aO2); respiratory index (RI= (PA-aO2)/PaO2), and content-based venous admixture (Qs/Qt). One of the issues with this approach is that these indices fail to take into consideration several additional external pulmonary physiological factors and, as such, these indices could potentially mislead clinicians. This thesis explores the nature of the oxygen-tension-based indices response and examined the effect that varying certain external pulmonary factors, such as FiO2, PaCO2, Hb, respiratory rate, oxygen consumption, cardiac output, and respiratory quotient, had on PaO2 using virtual subjects and patients’ data to quantify oxygenation defect through a combination of mathematics, different diseases, and pathophysiology. There were one or two approaches that could lead us to the answer, and many dead end routes. Eventually, the research produced a new index that was compared and validated using two approaches. First, on virtual subjects with lung pathologies that were commonly seen in the intensive care unit and then on real clinical data that was obtained from the intensive care unit. The results of these validation investigations indicated that the proposed index is more robust and resistant to variations in certain external pulmonary factors than the PaO2/FiO2 ratio. As such, there is a strong indication that it may help to improve the quality of patient care provided. The feasibility of manually calculating and applying this newly proposed index in the ICU is an issue that merits further exploration. Theoretically, if the newly proposed index was found to be practicable, it could improve the healthcare provided; reduce the cost of unnecessary blood work, and save time and effort. However, due to the time it takes to calculate crPaO2 manually, the use of medical technology and computer applications is desirable.

Introduction: Lung cancer is the commonest cause of cancer related death in men and women in England. In 2004 the National Lung Cancer Audit (NLCA) was created, as a national non-mandatory contemporary dataset of clinical features of individuals with lung cancer in part to identify variations in clinical practice and outcomes. The main aims of this dissertation are to determine the validity and representativeness of this dataset and then to investigate what factors influence access to surgery and chemotherapy and subsequent survival. In addition I have taken the opportunity afforded by this large dataset to describe the natural history of lung cancer in young adults (20-40 years). Methods: In order to establish if the dataset was representative, I created a measure of case ascertainment at the level of an NHS Trust, and examined the distribution of patient features and outcomes for varying levels of case ascertainment. I have then quantified the impact of patient and NHS Trust level features on access to surgery in people with non-small cell lung cancer and access to chemotherapy in people with small cell lung cancer using multivariate logistic regression. I have also conducted a series of survival analyses using Cox regression. Results: I have found no evidence that patient features vary systematically according to levels of case ascertainment in the NLCA. Age, sex, performance status, stage and co-morbidity all influenced the likelihood of having surgery for people with non-small cell lung cancer. Those patients first seen in a thoracic surgical centre where more likely to receive surgery than patients seen at peripheral centres (adjusted OR 1.51, 95% CI 1.16, 1.97), and surgery had a significant benefit on mortality (adjusted HR 0.41, 95% CI 0.39, 0.44). Although the resection rate was higher for patients first seen at a surgical centre (17% v 12%) these patients did equally well after surgery suggesting they were not a higher risk group. Individuals with small cell lung cancer first seen in a hospital with a high participation in clinical trials, (>5% of expected lung cancer patients being entered into clinical trials), were more likely to receive chemotherapy (adjusted OR 1.42, 95% CI 1.06, 1.90). Chemotherapy was associated with an improvement in survival (adjusted HR 0.51, 95% CI 0.46, 0.56), and amongst those patients receiving chemotherapy, mortality was not affected by the trial status of the hospital where they were first seen. In limited stage small cell disease, those patients who had chemo-radiotherapy had an improved survival compared with those patients who received chemotherapy alone (adjusted HR 0.72, 95% CI 0.62, 0.84). This dataset of English patients with lung cancer contains one of the largest cohorts of young adults (20-40 years) with lung cancer (N=583). I have been able to demonstrate that the majority present with a good performance status (0 or 1 in 80% of those with PS recorded), but advanced (stage IV) disease at diagnosis (55% of those with stage recorded). Those who have surgery have a survival profile similar to their older counterparts. Conclusion: The National Lung Cancer Audit is a representative, contemporary cohort of people with lung cancer, which can provide valuable information for health service research in lung cancer. I have found evidence that there is variation in access to treatment based on the facilities or the performance of individual NHS Trusts. My results suggest that by improving access to thoracic surgery for those individuals with non-small cell lung cancer we may be able to raise the resection rate and improve five year survival. The pattern is similar for people with small cell lung cancer and access to chemotherapy. What this research cannot explain is the aetiology for this variation, and where in the diagnostic pathway changes need to be made to improve the active management and access to potentially curative regimes. As the audit matures with more detailed information on NHS Trust level care, further analyses will be possible to try and determine more clearly what explains these variations, and how we might intervene to reduce them.

Background: The hypothesis that paracetamol may increase the risk of asthma and other allergic disease has gained consistent support from epidemiological studies, but evidence from longitudinal cohort studies, particularly those looking at the timing and dose of exposure are lacking. Epidemiological studies have also reported an inverse relation between gastro-intestinal infections including Helicobacter pylori, commensal bacteria and geohelminths and asthma and allergic disease, however, data from longitudinal birth cohort study are scarce. This thesis has therefore investigated the effects of paracetamol, H. pylori and other gastro-intestinal infections on the incidence and prevalence of allergic diseases and sensitization in a low-income birth cohort in which confounding by social advantage and other medical interventions is unlikely to play a role. Methods: In 2005/6 a population based cohort of 1065 pregnant women from Butajira, Ethiopia was established, to whom 1006 live singleton babies were born, and these children have been followed-up from birth to age five. At ages one, three and five, the International Study of Asthma and Allergies in Children (ISAAC) questionnaires were administered to the mothers to obtain data on wheeze, eczema and rhinitis. Allergen skin tests to Dermatophagoides pteronyssinus and cockroach were performed at ages three and five. Data on child's use of paracetamol, and various early life putative risk factors, including levels of Der p 1 and Bla g 1 allergen in the child's bedding and symptoms of respiratory tract infections were also measured. Stool samples were collected at ages three and five for analysis of H. pylori antigen using a rapid test (Medimar immunocard), as well as for geohelminths (at ages one, three and five) and selected commensal bacteria (at age three). Multivariate logistic regression was used to determine the independent effects of various markers of paracetamol use on the incidence of each outcome between age one and five, as well as on prevalence at age five. Similar analyses were also carried out to determine the independent effects of H. pylori, geohelminths and commensals on the incidence and prevalence of each outcome. Results: Effects of paracetamol: Of the 1006 children in the cohort at birth, 863 children were successfully followed up at age five (94% of surviving mother-child dyads). Wheeze and eczema incidence between the ages of one and five were reported in 5.9% (40/676) and 5.8% (39/700) of children respectively, and rhinitis and sensitization incidence between ages three and five were found in 3.9% (31/798) and 2.0% (15/766) of children respectively. Paracetamol use in the first three years of life was common, with 18% reported use at age one but not three, 23% at age three but not one and 21% at both time points. Use in the first year of life was significantly associated with a dose-dependent increased risk of incident wheeze between ages one and three (fully adjusted ORs, 95% CI, 1.77; 0.96, 3.26 for 1-3 tablets and 6.78; 1.89, 24.39 for ≥ 4 tablets in past month versus never), but not eczema. The risk of incident wheeze, eczema, rhinitis and sensitization between ages three and five was increased in those exposed, significantly so for incident eczema (p=0.02) and borderline significant for rhinitis (p=0.07), with fully adjusted odds ratios (ORs), including for symptoms of respiratory tract infections, for persistent exposure (ages one and three) versus never of 3.82 (95% CI 1.36, 10.73) and 3.10 (1.00, 9.57) respectively. Borderline significant trends were also seen between paracetamol dose in the first three years of life and incident eczema and rhinitis, with adjusted ORs for heavy reported use compared to low of 1.59 (0.44, 5.74; p trend=0.06) and 2.31 (0.72, 7.46; p trend=0.07) respectively, but not with incident wheeze (fully adjusted OR=3.64; 1.34, 9.90, p trend=0.11). Cross-sectional analysis at age five resulted in significant positive dose-response effects of lifetime use (use at ages one, three and five) in relation to the prevalence of all outcomes. Effects of gastro-intestinal infection H. pylori infection was found in 17% of the children at age three but not five, 21% at age five but not three years, and 25% at both ages. In the longitudinal analysis, H. pylori infection at age three was significantly associated with a decreased risk of incident eczema between ages three and five years (adjusted OR, 95% CI, 0.31; 0.10, 0.94, p=0.02), but the associations with incident wheeze, rhinitis and sensitization were not significant. In cross-sectional analysis at age three, H. pylori infection was associated with a borderline significant reduced risk of eczema (adjusted OR, 95% CI, 0.49; 0.24, 1.01, p=0.05) and D. pteronyssinus sensitization (adjusted OR, 95% CI, 0.42; 0.17, 1.08, p=0.07), and a significant inverse association between current exposure to H. pylori, and any sensitization at age five (adjusted OR, 95% CI, 0.26; 0.07, 0.92, p=0.02). However, no significant associations were seen for wheeze and rhinitis. The prevalence and intensity of geohelminth infection (hookworm, Ascaris lumbricoides and Trichuris trichiura) were found to be low in this cohort, with only 4% of children infected at age one, 9% at age three and only 0.2% at both ages. The risk of new onset wheeze between ages one and three was lower in those infected at age one (3.6%) than uninfected (7.8%), but infection was insufficiently prevalent to compute estimates of effect. Exposure to geohelminth infections in the first three years of life was not significantly associated with the incidence of reported outcomes or sensitization. However, A. lumbricoides infection was associated with a borderline increased risk of incident eczema between ages three and five (adjusted OR, 95% CI, 2.86; 1.04, 7.86, p=0.07). Children at age three were commonly colonized with enterococci 38% (207/544), lactobacilli 31% (169/544) and bifidobacteria 19% (103/544). However, none of these commensal bacteria were associated significantly with either incidence or prevalence of allergic outcomes. Conclusions: This longitudinal study from a developing country birth cohort provides further support for an association between early life use of paracetamol and increased risk of wheeze and allergic disease, which is unlikely to be explained by aspirin avoidance, reverse causation or confounding by indication. Furthermore, among young children in this cohort, the study found novel evidence to support the hypothesis of a protective effect of H. pylori infection on the risk of allergic disease, but no evidence to support an etiological role for the microflora enterococci, lactobacilli or bifidobacteria. The power of the study to explore the role of geohelminth infection on wheeze and allergic disease was limited by few infected children, and therefore understanding on this particular relation has not been much further advanced.

Rationale: Current asthma guidelines recommend reducing inhaled corticosteroid (ICS) therapy dose by 50% in patients with mild to moderate asthma who have demonstrated three months of good symptom control however there is evidence to suggest that this does not occur. Objectives: We tested whether exhaled nitric oxide (FeNO) measurements or other clinical indices could be utilised to predict a safe reduction of ICS dose, without provoking loss of symptom control or exacerbation within 3 months. We also investigated relationships between airway inflammation and asthma symptoms in the mild to moderate asthma cohort. Methods: 191 patients with stable asthma were recruited from primary care. Patients had their FeNO level measured at baseline and then had their inhaled corticosteroid (ICS) dose reduced by 50%. FeNO measurements were reassessed seven days later. The primary outcomes were whether baseline FeNO or a change in FeNO following ICS dose reduction could predict asthma stability at 3 months. Results: 128/191 patients (67%) completed the ICS dose reduction successfully at three months. 63/191 patients (33%) suffered from either a loss of control or an exacerbation. Baseline FeNO, or change in FeNO (post step-down minus pre step-down) were not statistically significantly different between the two groups. Conclusion: 67% of patients with well-controlled asthma can safely reduce their ICS dose by half without suffering from a loss of control or exacerbation within three months; however neither baseline nor change in FeNO measurements or routine clinical indices can be used to predict which patients can or cannot successfully tolerate a reduction in ICS dose.

Asthma is characterised by airway remodelling and an increase in airway resistance. A greater understanding of the mechanisms involved in airway inflammation and airway hyper-responsiveness (AHR) may highlight therapeutic opportunities for asthma. This study initially aimed to optimise the preparation of precision cut lung slices (PCLS) in mouse and pig to investigate the influence of calcium (Ca2+) homeostasis on airway smooth muscle (ASM) contraction as a prelude to human studies. The PCLS technique was then applied to a murine model of allergic airway disease to explore the inflammatory process and pathogenesis of airway hyper-reactivity in sensitised mice. Initial experiments using murine and porcine airways validated the PCLS model and demonstrated the significance of release and refilling of Ca2+ from internal stores to induce and maintain an airway contraction. Results also highlight interesting species differences in agonist sensitivity, with the porcine system sharing similar pharmacology to human airways. Using a murine model of allergic airway disease, agonist induced contractile responses in peripheral airways were measured in vitro using the PCLS technique. BALB/c mice underwent initial sensitisation by intraperitoneal administration of ovalbumin, receiving a 3 day challenge with aerosolised OVA l% (vlv), for varying periods of up to 3 weeks for acute, mid-chronic and chronic sensitisation protocols. To investigate the influence of the inflammatory environment, naive murine lung slices were incubated with selected inflammatory mediators. OVA sensitisation led to progressive structural remodelling and AHR to methacholine (MCh) challenge. However, this hyperresponsiveness was decreased 48 hours post lung removal. Of the inflammatory mediators selected for lung slice incubation, IL-33 significantly increased AHR to MCh. IL-33 is a proinflammatory cytokine with transcriptional repressor properties, playing a role in initiating the TH2 inflammatory response. In lung slices prepared from IL-33 receptor (ST2) KO mice IL-33 was unable to sensitise the contractile response. These data suggest the inflammatory environment promotes AHR and disassociates this airway sensitivity from structural remodelling. These data suggest a key role for IL-33 in mediating AHR in this murine model. Investigation of the mechanisms involved in airway hyper-reactivity revealed mRNA expression of IL-33 and the IL-33 receptor (ST2) in soluble and membrane bound forms were significantly increased in the mid-chronic and chronic ovalbumin sensitised murine lung tissue. Further quantitative analysis in human lung showed expression of IL-33 in epithelial and ASM cells. The human ST2 receptor (also known as IL-IRL-l) was expressed in mast cells. Together these results suggest IL-33 is a sensor of tissue damage; indirectly inducing AHR through further inflammatory cell activation to target ASM. This study demonstrates IL-33's role as an inflammatory marker of asthma and suggests a novel therapeutic intervention by targeting of the ST2 receptor.

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease with no effective treatment. Myofibroblasts contribute to the pathology of IPF by secreting large amounts of extracellular matrix proteins such as alpha smooth muscle actin (α-SMA) and Collagen I (Col 1). Myofibroblasts have reduced Prostaglandin E2 (PGE2), a key anti-fibrotic mediator, due to diminished cyclooxygenase-2 (COX-2) expression. Primary fibroblasts isolated from lungs of IPF patients (F-IPF) expressed significantly less COX-2 in response to IL-1β and increased α-SMA and Col I compared with fibroblasts isolated from lungs of non-fibrotic patients (F-NL). COX-2 was gradually lost in F-NL treated with transforming growth factor-β (TGF-β1), a pro-fibrotic cytokine, whereas PGE2, and cAMP elevating agents increased IL-1β-induced COX-2 expression in F-IPF. Ras, a small G protein, has been shown to have a role in several fibrotic conditions. Farnesylthiosalicylic acid (FTS), a Ras inhibitor, increased IL-1β-induced COX-2 and prevented TGF-β1-induced reduction of COX-2. Previous studies suggest that COX-2 is epigenetically repressed. LBH589, a HDAC inhibitor, prevented TGF-β1-induced repressed COX-2 whereas BIX01294, a DNA lysine methyltransferase inhibitor, and RG108, a G9a histone methyltransferase inhibitor, both increased IL-1β-induced COX-2 in F-IPF. In conclusion, the gradual loss of PGE2/COX-2 anti-fibrotic mechanism during myofibroblast differentiation may contribute to the pathophysiology of pulmonary fibrosis and agents that increase cAMP levels, inhibit Ras or inhibit epigenetic repression of COX-2, may compensate for the lack of endogenous PGE2.

Background Airways diseases are increasingly recognised to be poorly defined phenomena with overlapping pathophysiology and symptoms. They are a significant and growing cause of morbidity, with increasing numbers of people affected globally and no improvement in key outcomes in the UK for the last decade despite ever increasing expenditure. The classification of airway diseases has changed little in the last 50 years, and may no longer be fit for purpose due to the growing appreciation of the complexity and heterogeneity of airways disease and the advent of molecular-based diagnostic techniques to target specific treatment. Aim To investigate whether strategies based on the measurement of selected phenotypic and biological characteristics of airways disease can help to improve the understanding of their pathogenesis and targeting of treatment. Methods Three characteristics of airways disease, namely (1) exhaled nitric oxide, (2) chronic productive cough of unknown cause and (3) the airway microbiota were described/measured in selected cohorts of patients in three clinical studies. Measurement of each of these characteristics was used to answer focused clinical questions regarding the pathogenesis and treatment of aspects of airways disease. Results (1) The baseline measurement of FENO in steroid naïve subjects with symptoms suggestive of asthma had a low diagnostic value for asthma but was an excellent predictor of inhaled steroid treatment response. (2) A cohort of subjects with chronic productive cough of unknown cause was described. These subjects tended to have radiological evidence of airway dilatation and chronic inflammatory changes but not significant bronchiectasis. Their cough responded well to treatment with azithromycin, with ongoing neutrophilic airway inflammation a particularly strong predictor of treatment response. (3) There were no significant differences in the abundance or community structure of the bacterial communities in the airways between subjects with mild (BTS 2) or severe (BTS 4) asthma or between severe (BTS 4) asthma patients taking inhaled fluticasone or budesonide. However a number of differences in relative abundance of certain species (including enrichment of Haemophilus parainfluenzae in the fluticasone group) were noted on comparison of the groups. Conclusions This thesis provides support for a new approach to the classification and treatment of airways disease. The recognition of pathologically important processes (treatable traits) which can be used to predict response to targeted treatment has the potential to revolutionise the management of airways disease and result in improved patient outcomes.

The urokinase plasminogen activator receptor (uPAR, PLAUR) is a cell surface receptor actively involved in the regulation of cell homeostasis. Expression is elevated in the bronchial epithelium in vivo and also in serum and sputum in asthma and elevated expression often indicates poor prognosis in a number of human diseases. The relative contribution of uPAR to asthma disease mechanisms is not fully understood and the functional roles of uPAR isoforms remains to be resolved. The key aims of this thesis were to i) investigate how the uPAR pathway may influence bronchial epithelial barrier properties; ii) investigate the gene expression patterns in the bronchial epithelium in asthma; iii) identify functions of different forms of uPAR in human bronchial epithelial cells (HBEC) and to iv) investigate the association between genetic polymorphisms spanning the PLAUR gene with clinical features and the presentation of asthma in moderate to severe asthma. Using two cell based approaches we identified an inverse relationship between soluble-cleaved uPAR expression and epithelial barrier properties. Importantly, we demonstrated that blocking uPAR-integrin interactions provides a potential therapeutic opportunity to improve epithelial barrier function. Using whole transcriptome analysis genes differentially expressed between cultured asthma and control subjects were identified which were related to cell growth, repair and immune regulation. Furthermore, uPAR expression was elevated in epithelial cells in asthma subjects compared to healthy controls, suggesting expression is inherently altered in the bronchial epithelium in asthma. Transcriptomics was used to provide novel insight into the specific and overlapping functions of uPAR isoforms and to determine the effects of elevated uPAR expression on HBEC function. Finally, the contribution of PLAUR genetic variants to clinical and immunological traits within asthma were investigated and found that PLAUR single nucleotide polymorphisms (SNPs) did not show an association with the traits measured in a severe asthma population. Overall this work has provided new insight into the function of uPAR as a regulator of the bronchial epithelium in asthma.