Linkage analysis of bronchial hyperreactivity and atopy with chromosome 11q13

Gene-environment interactions and airway disease in children

Asthma is the most common chronic disease of childhood in the United States, affecting nearly 6.5 million children. The prevalence and severity of childhood asthma have continued to increase over the past 2 decades, despite major advances in the recognition and treatment of this condition. Representing a heterogeneous collection of airway diseases, asthma has multiple pathologic processes resulting from the interactions of genetic susceptibility and environmental exposures. Preventing and treating airway disease in children will require new research approaches to understanding these complex interactions.

Allergy-associated polymorphisms of the Fc epsilon RI beta subunit do not impact its two amplification functions

Two variants of the beta-chain of the high affinity IgE receptor Fc epsilon RI, I181L-V183L and E237G, have been found associated with allergy. We have previously shown that the beta-chain plays at least two distinct amplifier functions. It amplifies Fc epsilon RI surface expression and signaling, resulting in an estimated 12- to 30-fold amplification of downstream events. To test the hypothesis that the I181L-V183L and E237G beta variants may be functionally relevant and could directly contribute to an allergic phenotype, we have evaluated the functional impact of the beta variants on the two amplifier functions of beta. We found that these variants have no direct effect on the beta amplifier functions. However, the possibility remains that these variants are in linkage disequilibrium with other more relevant polymorphisms or are affecting unknown beta-chain functions.

Asymptomatic bronchial hyperresponsiveness to exercise in childhood and the development of asthma related symptoms in young adulthood: the Odense Schoolchild Study

BACKGROUND

Exercise testing may be of value in identifying a group of children at high risk of subsequently developing respiratory symptoms. As few longitudinal studies have investigated this issue, the bronchial hyperresponsiveness to exercise in asymptomatic children was evaluated as a risk factor for developing asthma related symptoms in young adulthood.

METHODS

A community based sample of 1369 schoolchildren, first investigated in 1985 at a mean age of 9.7 years, was followed up after a mean of 10.5 years. Nine hundred and twenty children (67%) were asymptomatic in childhood and 777 (84.9%) of these were re-investigated at follow up. At the first examination a maximum progressive exercise test on a bicycle ergometer was used to induce airway narrowing. The forced expiratory volume in one second (FEV1) after exercise was considered abnormal if the percentage fall in FEV1 was more than 5% of the highest fall in the reference subjects characterised by having no previous history of asthma or asthma related symptoms. The threshold for a positive test was 8.6% of pre-exercise FEV1.

RESULTS

One hundred and three subjects (13%) had wheeze within the last year at follow up and, of these, nine (9%) had been hyperresponsive to exercise in 1985. One hundred and seventy subjects (22%) had non-infectious cough within the previous year, 11 of whom (6%) had been hyperresponsive to exercise in 1985. Multiple regression analysis showed that subjects with hyperresponsiveness to exercise had an increased risk of developing wheeze compared with subjects with a normal response to exercise when the fall in FEV1 after exercise was included as a variable (threshold odds ratio (OR) 2.3 (95% CI 1.1 to 5.5)). The trend was not significant when exercise induced bronchospasm was included as a continuous variable (OR 1.02 (95% CI 0.97 to 1.06)).

CONCLUSIONS

Asymptomatic children who are hyperresponsive to exercise are at increased risk of developing new symptoms related to wheezing but the predictive value of exercise testing for individuals is low.

The high-affinity IgE receptor (Fc epsilon RI): from physiology to pathology

The high affinity receptor for immunoglobulin E (designated Fc epsilon RI) is the member of the antigen (Ag) receptor superfamily responsible for linking pathogen-or allergen-specific IgEs with cellular immunologic effector functions. This review provides background information on Fc epsilon RI function combined with more detailed summaries of recent progress in understanding specific aspects of Fc epsilon RI biology and biochemistry. Topics covered include the coordination and function of the large multiprotein signaling complexes that are assembled when Fc epsilon RI and other Ag receptors are engaged, new information on human receptor structures and tissue distribution, and the role of the FcR beta chain in signaling and its potential contribution to atopic phenotypes.

Chromosome 11q13 and atopic asthma

Asthma is a complex syndrome in which bronchial inflammation and smooth muscle hyperactivity lead to labile airflow obstruction. The commonest form of asthma is that due to atopy, which is an immune disorder where production of IgE to inhaled antigens leads to bronchial mucosal inflammation. The ultimate origins of asthma are interactive environmental and genetic factors. The genetics is acknowledged to be heterogeneous, and one chromosomal region of interest and controversy has been 11q13. To clarify the nature of the chromosome 11q13 effect in atopy and asthma, we conducted a genetic association study in subjects with marked atopic asthma and matched controls, which incorporated the study of 13 genetic variants over a distance of 10-12 cM and which took account of detailed immune and clinical phenotyping. Association with high IgE levels was limited to the interval flanked by D11S1335 and CD20 in a 0.8-Mb interval and was greatest for variants of Fc epsilonRIbeta and HTm4; these variants also associated with asthma (recurrent wheeze with labile airflow obstruction and need for regular inhaler treatment). At the more telomeric marker, D11S480, variants associated with asthma, but not with high IgE levels. The data might support the possibility of multiple loci relevant to atopic asthma on chromosome 11q13.

Genetic factors in preterm delivery

Tens of thousands of children deliver before they are full term each year. Although many social, environmental, and medical risk factors have been suggested, the etiology of a large percentage of preterm labor cases is still unknown. It has been noted for many years that preterm delivery is a condition that runs in families. Evidence concerning its aggregation among families, the recurrent nature of preterm labor, and its differing prevalence between races has led to the suggestion of a genetic cause for preterm delivery. There have been few formal studies to investigate this hypothesis. We suggest that modern molecular biology approaches can reveal the part that genes play in preterm delivery.