IL-5 PRODUCTION BY BRONCHOALVEOLAR LAVAGE AND PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN ASTHMA AND ATOPY

There is increasing evidence to suggest a key role for interleukin-5 ( IL-5) in the regulation of airway eosinophilia in asthma. We compared the capacity for IL-5 production in atopic asthmatic, nonatopic asthma tic, atopic nonasthmatic and normal subjects, and evaluated the useful ness of peripheral blood cells for reflecting airway cell reactivity. Bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear ce lls (PBMC) from 12 atopic and 10 nonatopic asthmatics (without inhaled steroid therapy), 9 atopic nonasthmatics, and 10 normal controls were cultured with or without house dust mite (HDM, 10 mu g . mL(-1)) stim ulation. CD4+ T-cell activation, IL-5 and interferon-gamma (IFN-gamma) production in the cultures were assessed. Both for BAL and PBMC sampl es, atopic and nonatopic asthmatic subjects showed comparable spontane ous production of IL-5, which was significantly higher than that eithe r for atopic nonasthmatics or normal controls (p<0.05 or p<0.01). Ther e was a significant correlation between the percentage of eosinophils in BAL and spontaneous production of IL-5 by BAL cells in both asthmat ic groups (p<0.05 or p<0.01). Both these parameters were also associat ed with asthmatic airway narrowing as denoted by a negative relationsh ip with baseline forced expiratory volume in one second (FEV1) as perc entage predicted (p<0.05 and p<0.01, respectively). In contrast, IFN-g amma production by unstimulated BAL cells from normal controls was hig her than that for BAL cell cultures of nonatopic asthmatic subjects (p <0.05). Following HDM stimulation, both atopic groups had comparable p ositive responses in terms of CD4+ T-cell activation, but there was re latively greater IL-5 production in asthmatic PBMC (p<0.05) and, in pa rticular, BAL cell cultures (p<0.01). These findings suggest that elev ated IL-5 production is a common feature of BAL cells and PBMC in atop ic and nonatopic asthma. In addition, atopic asthmatics show greater I L-5 production in response to specific allergen compared with atopic n onasthmatics, an effect most marked in BAL cells compared to PBMC. Hen ce, peripheral blood mononuclear cells can reflect cytokine immunoreac tivity of airway cells, but lack local cellular interactions, which li mits their usage in asthma research.