Immunopathology of allergy and asthma in childhood

Comorbidities of asthma and the unified airway

BACKGROUND

Asthma is a comorbid condition that may be seen by otolaryngic allergists when treating their patients with allergic rhinitis (AR). Often asthma is overlooked when aggressive treatment could prevent the development or progression of early disease.

METHODS

This article is a retrospective review of the current literature on asthma as a comorbidity of the unified airway. The unified airway and asthma are clearly defined. The epidemiology, morbidity, mortality, pathophysiologic mechanisms, and the chronicity of asthma are reviewed.

RESULTS

The otolaryngic allergist will become familiar the unified airway concept and the close relationships between AR, chronic rhinosinusitis, and asthma.

CONCLUSION

Otolaryngologists should be aware of the unified airway in order to most effectively treat their patients with AR. Knowledge of the close relationships between asthma and AR will help prevent progression of disease, identify early asthma, and improve the outcomes and quality of life for our patients.

Asthma and the otolaryngologist

BACKGROUND

Asthma is a chronic inflammatory disease of the lower airway that is commonly encountered by the otolaryngologist. This article provides information on how to recognize patients with asthma and discuss issues related to diagnosis, treatment, and continued management within the context of current guidelines.

METHODS

A literature review was conducted and relevant sources are referenced concerning the epidemiology of asthma, the pathophysiology of asthma, diagnostic strategies, treatment options, and continued management.

RESULTS

Asthma is a common condition worldwide and is often associated with other atopic diseases such as allergic rhinitis and eczema, though other genetic and environmental factors appear to be important as well. The lower airway and upper airways share similar histology, as well as patterns of inflammation in response to environmental triggers. The diagnosis of asthma involves a careful history and a complete physical exam, including auscultation of the lungs and pulmonary function testing. Pharmacotherapy represents the primary method of treating asthma, though current evidence supports a positive role for antigen-specific immunotherapy for both prevention and treatment. Guidelines are available that can assist the otolaryngologist in classifying the severity of asthma, determining the level of control and recommending modifications in the treatment plan.

CONCLUSION

As airway specialists, otolaryngologists are in a unique position to recognize and manage asthma in their patients, particularly those with allergic disease. Maintaining a high index of suspicion and understanding the key elements of diagnosis and treatment are extremely important in order to achieve this goal.

Why otolaryngologists and asthma are a good match: the allergic rhinitis-asthma connection

Consideration of the unified airway model when managing patients with rhinitis and or asthma allows a more comprehensive care plan and therefore improved patient outcomes. Asthma is linked to rhinitis both epidemiologically and biologically, and this association is even stronger in individuals with atopy. Rhinitis is not only associated with but is a risk factor for the development of asthma. Management of rhinitis improves asthma control. Early and aggressive treatment of allergic rhinitis may prevent the development of asthma. In patients with allergic rhinitis that is not sufficiently controlled by allergy medication, allergen-directed immunotherapy should be considered.

Maternal exposure to secondhand cigarette smoke primes the lung for induction of phosphodiesterase-4D5 isozyme and exacerbated Th2 responses: rolipram attenuates the airway hyperreactivity and muscarinic receptor expression but not lung inflammation and atopy

Airway hyperreactivity (AHR), lung inflammation, and atopy are clinical signs of allergic asthma. Gestational exposure to cigarette smoke (CS) markedly increases the risk for childhood allergic asthma. Muscarinic receptors regulate airway smooth muscle tone, and asthmatics exhibit increased AHR to muscarinic agonists. We have previously reported that in a murine model of bronchopulmonary aspergillosis, maternal exposure to mainstream CS increases AHR after acute intratracheal administration of Aspergillus fumigatus extract. However, the mechanism by which gestational CS induces allergic asthma is unclear. We now show for the first time that, compared with controls, mice exposed prenatally to secondhand CS exhibit increased lung inflammation (predominant infiltration by eosinophils and polymorphs), atopy, and airway resistance, and produce proinflammatory cytokines (IL-4, IL-5, IL-6, and IL-13, but not IL-2 or IFN-gamma). These changes, which occur only after an allergen (A. fumigatus extract) treatment, are correlated with marked up-regulated lung expression of M1, M2, and M3 muscarinic receptors and phosphodiesterase (PDE)4D5 isozyme. Interestingly, the PDE4-selective inhibitor rolipram attenuates the increase in AHR, muscarinic receptors, and PDE4D5, but fails to down-regulate lung inflammation, Th2 cytokines, or serum IgE levels. Thus, the fetus is extraordinarily sensitive to CS, inducing allergic asthma after postnatal exposure to allergens. Although the increased AHR might reflect increased PDE4D5 and muscarinic receptor expression, the mechanisms underlying atopy and lung inflammation are unrelated to the PDE4 activity. Thus, PDE4 inhibitors might ease AHR, but are unlikely to attenuate lung inflammation and atopy associated with childhood allergic asthma.

Asthma and the unified airway

Inflammatory processes of the upper and lower airway commonly co-exist. Patients with upper respiratory illnesses such as allergic rhinitis and acute and chronic rhinosinusitis often present to both otolaryngologists and primary care physicians for treatment of their symptoms of nasal and sinus disease. These patients often have concurrent lower respiratory illnesses such as asthma that may be contributing to their overall symptoms and quality of life. Unfortunately, asthma frequently remains undiagnosed in this population. It was the objective of this paper to examine the relationship between upper respiratory illnesses such as rhinitis and rhinosinusitis and lower respiratory illnesses such as asthma, and to provide a framework for primary care and specialty physicians to approach these illnesses as a spectrum of inflammatory disease. The present manuscript was developed by a multidisciplinary workgroup sponsored by the American Academy of Otolaryngic Allergy. Health care providers in various specialties contributed to the manuscript through preparation of written materials and through participation in a panel discussion held in August 2006. Each author was tasked with reviewing a specific content area and preparing a written summary for inclusion in this final document. Respiratory inflammation commonly affects both the upper and lower respiratory tracts, often concurrently. Physicians who are treating patients with symptoms of allergic rhinitis and rhinosinusitis must be vigilant to the presence of asthma among these patients. Appropriate diagnostic methods should be used to identify individuals with concurrent respiratory illnesses, and comprehensive treatment should be instituted to reduce symptoms and improve quality of life.

Exhaled nitric oxide as a screening tool for asthma in school children

It is now widely accepted that augmented levels of fractional exhaled nitric oxide (FeNO) reflect airway inflammation and the methodology has been optimised for potential clinical use. We were interested in investigating whether this measurement can be used as a tool to screen and identify school children with asthma. To do this, FeNO was measured using an on-line single exhalation analyser in 368 children aged 8-10 years in six Oxfordshire primary schools, by two investigators blinded to the disease status of the children. The children were then categorised into 'normal', 'atopic asthma', 'non-atopic asthma' and 'atopy only' groups, according to their responses to the ISAAC questionnaire and perusal of the children's medical records kept by their family practitioners. Increased levels of FeNO were found in 'atopic asthmatic', 'non-atopic asthmatics' and 'atopic only' groups (median values of 24.4, 7.8 and 15.3 ppb, respectively, compared to normal controls' of 6.9 ppb). Levels were increased in atopic children regardless of whether they had asthma and were significantly higher than non-atopic asthmatics. We conclude that FeNO measurement is not a useful tool for identifying children with asthma in the community, as increased levels did not discriminate between those with asthmatic and atopic symptoms.

Second-hand smoke increases nitric oxide and alters the IgE response in a murine model of allergic aspergillosis

This study was performed to determine the effects of environmental tobacco smoke (ETS) on nitric oxide (NO) and immunoglobulin (Ig) production in a murine model of allergic bronchopulmonary aspergillosis (ABPA). Adult BALB/c mice were exposed to aged and diluted sidestream cigarette smoke from day 0 through day 43 to simulate “second-hand smoke”. During exposure, mice were sensitized to soluble Aspergillus fumigatus (Af) antigen intranasally between day 14 and 24. All Af sensitized mice in ambient air (Af + AIR) made elevated levels of IgE, IgG1, IgM, IgG2a and IgA. Af sensitized mice housed in ETS (Af + ETS) made similar levels of immunoglobulins except for IgE that was significantly reduced in the serum and bronchoalveolar lavage (BAL). However, immunohistochemical evaluation of the lung revealed a marked accumulation of IgE positive cells in the lung parenchyma of these Af + ETS mice. LPS stimulation of BAL cells revealed elevated levels of NO in the Af + AIR group, which was further enhanced in the Af+ETS group. In vitro restimulation of the BAL cells on day 45 showed a TH0 response with elevated levels of IL3, 4, 5, 10 and IFN-γ. However, by day 28 the response shifted such that TH2 cytokines increased while IFN-γ decreased. The Af + ETS group showed markedly reduced levels in all cytokines tested, including the inflammatory cytokine IL6, when compared to the Af+AIR group. These results demonstrate that ETS affects ABPA by further enhancing the NO production and reduces the TH2 and the inflammatory cytokines while altering the pattern of IgE responses.

Eosinophil granule proteins in the assessment of airway inflammation in pediatric bronchial asthma

Eosinophil granule proteins such as eosinophil cationic protein (ECP), eosinophil peroxidase (EPO) and eosinophil protein X (EPX) in serum and urine are indirect measures of eosinophil activity. The measures have been evaluated for prediction, diagnosis and monitoring of anti-inflammatory treatment modalities in children with asthma. Assessments in serum and urine are highly dependent on sampling procedures and must be performed under strictly controlled conditions using standardized sampling and laboratory procedures. The measures are influenced by circadian and seasonal variations. Measurement of the eosinophil granule proteins does not improve the predictive value of a family history of atopy. Due to insufficient sensitivity and specificity, the measures are not useful in the diagnosis of asthma in children, and the clinical use of eosinophil proteins in the individual child for assessment of asthma severity has not been sufficiently validated. Serum and urine eosinophil granule proteins, however, may be useful in extending our knowledge of suppressive effects on eosinophil activity of various doses, devices and administration regimens of inhaled glucocorticoids in children. Such evaluations may be performed in randomized, double-blind trials of well-defined age groups and they should include measures of compliance. One important aspect to look at would be the distinction between suppressive effects on eosinophil activity and clinically important anti-inflammatory effects. Considering the complexity of airway inflammation and the heterogeneity of childhood asthma, however, it may be too simplistic to look for a single measure of the inflammatory processes. In the future, perhaps, a combination of products of inflammatory cells may give more clinically relevant information with respect to prediction, diagnosis, monitoring and outcome of childhood asthma.