Comparison of allergen-induced changes in bronchial hyperresponsiveness and airway inflammation between mildly allergic asthma patients and allergic rhinitis patients

Bronchial eosinophilic inflammation and bronchial hyperresponsiveness (BHR) are the main features of allergic asthma (AA), but they have also been dem onstrated in allergic rhinitis (AR), suggesting a continuity between both d iseases. In spite of not fully reproducing natural allergenic exposure, the allergen bronchial provocation test (A-BPT) has provided important knowled ge of the pathophysiology of AA. Our aim was to verify the existence of a b ehavior of AA and AR airways different from the allergen bronchial challeng e-induced airway eosinophilic inflammation and BHR changes. We studied a gr oup of 31 mild and short-evolution AA and 15 AR patients, sensitized to Der matophagoides pteronyssinus. The A-BPT was performed with a partially biolo gically standardized D. pteronyssinus extract, and known quantities of Der p 1 were inhaled. Peripheral blood (eosinophils and ECP) and induced sputum (percentage cell counts, ECP, albumin, tryptase, and interleukin [IL]-5) w ere analyzed, before and 24 h after A-BPT. Methacholine BHR, assessed befor e and 32 h after the A-BPT, was defined by M-PD20 values and, when possible , by maximal response plateau (MRP). The A-BPT was well tolerated by all th e patients. AA presented a lower Der p 1 PD20 and a higher occurrence of la te-phase responses (LPR). M-PD20 values decreased in AA, but not in AR, pat ients. MRP values increased in both groups. Eosinophils numbers and ECP lev els increased in blood and sputum from both AA and AR, but only the absolut e increment of sputum ECP levels was higher in AA than AR patients (P = 0.0 25). The A-BPT induced no change in sputum albumin, tryptase, or IL-5 value s. We conclude as follows: 1) In spite of presenting a lower degree of bronchial sensitivity to allerg en, AR patients responded to allergen inhalation with an eosinophilic infla mmation enhancement very similar to that observed among AA. 2) MRP levels increased in both AA and AR patients after allergen challenge ; however, M-PD20 values significantly changed only in the AA group, sugges ting that the components of the airway response to methacholine were contro lled by different mechanisms. 3) It is possible that the differences between AR and AA lie only in the qu antitative bronchial response to allergen inhalation.