Abstract
The prevalence of asthma, in particular atopic asthma, has markedly increased in recent years. Accumulating evidence suggests that environmental factors associated with allergic sensitization and exposure to microbial stimuli during infancy and early childhood, are associated with these changes in prevalence. However, considerable controversy surrounds the role of microbial agents, as evidence has been presented for both positive and negative effects in this context.
The review below focuses upon interactions between immune competence during infancy, the development of T‐helper (Th)1-polarized versus Th2-polarized memory against inhalant allergens, and susceptibility to virus infection. In particular, recent finding are highlighted which suggest that delayed postnatal maturation of Th1 function is associated with increased risk for early postnatal sensitization to inhalant allergens, and also with risk for viral bronchiolitis during infancy.
Variations in the kinetics of postnatal maturation of T‐helper 1 function may in part be attributable to polymorphisms in the CD14 gene, which influence host responsiveness both to bacterial as well as viral stimuli.
Footnotes
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↵Previous articles in this Series: No. 1: Pilette C, Ouadrhiri Y, Godding V, Vaerman J‐P, Sibille Y. Lung mucosal immunity: immunoglobulin‐A revisited. Eur Respir J 2001; 18: 571–588. No. 2: Lambrecht BN, Prins J‐B, Hoogsteden HC. Lung dendritic cells and host immunity to infection. Eur Respir J 2001; 18: 692–704. No. 3: Moore BB, Moore TA, Toews GB. Role of T‐ and B‐lymphocytes in pulmonary host defences. Eur Respir J 2001; 18: 846–856. No. 4: Message SD, Johnston SL. The immunology of virus infection in asthma. Eur Respir J 2001; 18: 1013–1025. No. 5: Crameri R, Blaser K. Allergy and immunity to fungal infections and colonization. Eur Respir J 2002; 19: 151–157. No. 6: De Rose V. Mechanisms and markers of airway inflammation in cystic fibrosis. Eur Respir J 2002; 19: 333–340.
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