ALLERGEN-SPECIFIC NASAL CHALLENGE - RESPONSE KINETICS OF CLINICAL ANDINFLAMMATORY EVENTS TO RECHALLENGE

Allergen-specific nasal challenge is a valid and reliable tool for stu dying the pathophysiological mechanisms involved in allergic inflammat ion. Nasal challenge induces an immediate clinical response in allergi c subjects and a concomitant appearance of an inflammatory infiltrate. The mucosal inflammation may persist up to 48-72 h after allergen exp osure. If the subjects are rechallenged within this period the respons e is more pronounced: the so-defined priming effect. The aim of the st udy was to evaluate the effects of the nasal rechallenge, performed at different time intervals: 3 days, 1, 2 and 4 weeks after the first ch allenge. Forty allergic subjects underwent two nasal challenges: at ba seline and after the periods mentioned above (10/group). Symptoms and inflammatory cells (eosinophils and neutrophils recovered by nasal bru shing) were assessed. The 3-day-interval group showed a hyperreactive response (priming effect), the 1- and 4-week-interval groups showed a response similar to baseline, and the 2-week-interval group showed a h yporeactive response ('tolerogenic effect'). The last phenomenon may b e due to a possible immunologic response similar to that achievable du ring local specific immunotherapy. The present results further elucida te the kinetics of allergen-driven inflammatory events and highlight t he importance of the time period chosen for rechallenge. The latter fa ct may be of primary importance in clinical trials involving specific challenge.