INCREASED EXPRESSION OF HIGH-AFFINITY IGE (FC-EPSILON-RI) RECEPTOR-ALPHA CHAIN MESSENGER-RNA AND PROTEIN-BEARING EOSINOPHILS IN HUMAN ALLERGEN-INDUCED ATOPIC ASTHMA

Fc epsilon RI receptors play an important role in allergen-induced med iator release and antigen presentation by mast cells, basophils, and m onocyte/macrophages in atopic disorders. The expression of Fc epsilon RI by tissue eosinophils in atopic asthma after allergen challenge has not been established. Far this reason we attempted to identify mRNA a nd protein product + Fc epsilon RI alpha eosinophils in cytospins made from bronchoalveolar lavage (BAL) from atopic asthmatics (n = 9) and nonatopic normal subjects (n = 4) 24 h after segmental challenge with allergen or diluent. Messenger RNA for Fc epsilon RI alpha was determi ned using in situ hybridization and Fc epsilon RI alpha protein expres sion by immunocytochemistry using a mouse monoclonal antibody 22E7. Co localization of FceRIa receptors to eosinophils was performed using ch romotrope 2R. When compared with a control challenge, segmental challe nge with Dermotophagoides pteronyssinus induced significant BAL eosino philia (p = 0.007). The total number of BAL Fc epsilon RI alpha mRNA a nd protein-positive cells also increased in asthmatics, median values 2 (0.7-7.2) and 11.5 (0.6-65.0) x 10(6) cells (p = 0.02) and 0 (0-0.3 x 10(6)) and 3.1 x 10(6) (0.45 - 162.5 x 10(6)) cells (p = 0.007), res pectively, for mRNA and protein. Net increases in Fc epsilon RI alpha cells correlated with the net increases in BAL eosinophils (r = 0.98, p = 0.0001 for mRNA and r = 0.72 p = 0.02 for protein). Colocalizatio n studies with chromotrope 2R revealed that only 4% of Fc epsilon RI a lpha+ cells were eosinophils after control challenge and, in contrast, 85 to 95% of Fc epsilon RI alpha+ cells were eosinophils after allerg en. There were no differences in the numbers of Fc epsilon RI alpha+ c ells or eosinophils in normal control subjects. Our results demonstrat ed that local endobronchial allergen provocation in atopic asthmatics results in increased synthesis and expression of Fc epsilon RI alpha p redominantly on BAL eosinophils.