Atopic asthma is associated with activation in the bronchi of the interleukin-3, 4, and 5 and GM-CSF gene cluster, a pattern compatible with predominant activation of the TH2-like T-cell population.

Intrinsic (nonatopic) asthma is considered to be a distinct pathogenetic variant of asthma since, unlike extrinsic (atopic) asthma, patients with the disease are skin test-negative to common aeroallergens, and have total serum IgE concentrations within the normal range. Nevertheless, the recent demonstration of increased numbers of cells expressing the high-affinity IgE receptor in bronchial biopsies from atopic and nonatopic asthmatic subjects, together with epidemiologic evidence indicating that serum IgE concentrations relate closely to asthma prevalence regardless of atopic status, suggests that IgE-mediated mechanisms may participate in the pathogenesis of both atopic and nonatopic asthma. Furthermore both variants of the disease are associated with bronchial mucosal eosinophilic inflammation. Interleukin-4 (IL-4) is an essential cofactor for IgE synthesis, and there is strong evidence that IL-5 plays a major role in eosinophil accumulation in asthmatic inflammation. For these reasons we compared the expression of IL-4 and IL-5 mRNA and protein product using a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) amplification, in situ hybridization, and immunohistochemistry in bronchial biopsies from symptomatic atopic and nonatopic asthmatic subjects and atopic and nonatopic controls. The results showed that as compared with controls, biopsies from both groups of asthmatic subjects had increased numbers of IL-4 and IL-5 mRNA copies relative to beta-actin mRNA as detected by RT-PCR. Similarly, in situ hybridization and immunohistochemistry demonstrated increased numbers of cells expressing IL-4 and IL-5 mRNA and protein in asthmatic subjects, irrespective of their atopic status. We conclude that individuals with either atopic or nonatopic asthma show infiltration of the bronchial mucosa with cells expressing Th2-type cytokines, providing further evidence for similarities in the immunopathogenesis of these clinically distinct forms of asthma.

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Asthma is characterized by bronchial mucosal inflammation. Although allergen-induced activation of cells binding allergen-specific immunoglobulin E (IgE) through high-affinity receptors (Fc(epsilon)RI) is believed to play some role in asthma, inappropriate synthesis of total or allergen-specific IgE cannot be demonstrated in some ("intrinsic") patients despite the fact that the nature of the bronchial inflammation is similar to that in atopic ("extrinsic") asthmatics. We have studied the numbers and phenotype of Fc(epsilon)RI-bearing cells in bronchial biopsies from 12 atopic and 10 nonatopic asthmatic patients and compared our findings with 10 atopic and 12 nonatopic control subjects using single and double immunohistochemistry. Significantly increased numbers of Fc(epsilon)RI-bearing cells were identified in bronchial biopsies from atopic and nonatopic asthmatics and atopic control subjects when compared with normal controls (p = 0.001, 0.006, and 0.0006, respectively). In asthmatics and atopics the majority of Fc(epsilon)RI-bearing cells were identified as mast cells and macrophages; a much smaller percentage were eosinophils. We conclude that elevated numbers of high-affinity IgE receptor-bearing cells are a feature of bronchial biopsies of asthmatic subjects, irrespective of their atopic status.

In dual responders with asthma, the 24-hour increase in airway wall cellular inflammation after allergen challenge resolves by 7 days, whereas the increases in AHR and markers of remodeling persist.