Background Dendritic cells (DC) are the most potent antigen-presenting cells (APC) and stimulators of T cells. Dendritic cells are also likely to be essential for the initiation of allergic immune responses in the lung. However, there are not many data on the presence of dendritic cells in the airways of patients with atopic asthma and on the effects of corticosteroid-treatment on such dendritic cells.
Objective We investigated the distribution of dendritic cells in the bronchial epithelium and mucosa of 16 non-smoking atopic asthmatic patients and eight healthy control subjects using detailed immunohistochemistry (CD l a, HLA-DR, L25 as markers for dendritic cells).
Methods Eleven asthmatics were treated for 2.5 years with bronchodilators only and five with bronchodilators and inhaled beclomethasone dipropionate (BDP), 800 μg daily. The patients were randomly sampled from a double-blind multicentre study. Results There were higher numbers of CD la+ DC (P = 0.003), L25+ DC (P = 0.002) and HLA-DR expression (P = 0.042) in the bronchial mucosa of asthmatic patients compared with healthy controls. After 2.5 years of treatment, we found a significant increase in fiow expiratory volume in I second (FEV1) (P = 0.009) and a significant decrease in hyperresponsiveness (PC20 histamine) (P= 0.013) in the corticosteroid group (n = 5) compared with the bronchodilator group (n= 11). This dinical improvement in the corticosteroid-treated group was accompanied by significantly lower numbers of CDla+ DC (P = 0.008), and HLA-DR expression (P- 0.028) in the bronchial mucosa than in the bronchodilator-treated group.
Conclusion Our data suggest that dendritic cells are involved in asthmatic inflammation and that corticosteroids may downregulute the number of dendritic.