Early and late phase asthmatic response in lower airways of cat-allergic asthmatic patients--a comparison between experimental and environmental allergen challenge.

BACKGROUND: Standardized experimental allergen challenges are usually adopted to investigate the effect of allergen exposure on the lower airways. Environmental (natural) allergen challenges are used less often, mainly because of difficulties in standardizing the method, safety reasons and costs. The aim of this study was to investigate the relationship between an experimental and an environmental bronchial challenge. For this reason a natural challenge model was developed. METHODS: Sixty-two patients with a history of cat allergen-induced symptoms involving the lower airways, positive skin prick test, positive in vitro specific IgE to cat allergen and bronchial hyper-responsiveness were included. All 62 patients underwent an experimental challenge in the laboratory followed by an environmental allergen challenge. RESULTS: All 62 patients developed an early asthmatic response [>or=20% fall in forced expiratory volume in 1 s (FEV1)] in the experimental challenge and 60% (37/62) during the environmental challenge. A late asthmatic response (>or=15% fall in FEV1 within 3-24 h) was seen in 56% (35/62) of the patients after the experimental challenge. Following the environmental challenge 47% (29/62) of the patients developed a late response. Thirty-four per cent (21/62) of the patients developed a late response in both challenge models and 31% (19/62) did not develop a late response in any model. Thus, there was consistency in 65% (40/62) of the patients in both challenge models. CONCLUSION: We found consistency in the pattern of response to inhaled allergen between the two challenge models and we believe that experimental bronchial challenge is likely to reflect the development of relevant inflammation in the lower airways after low-dose allergen exposure in the environment.

Allergen specific immunotherapy attenuates early and late phase reactions in lower airways of birch pollen asthmatic patients: a double blind placebo-controlled study.

BACKGROUND: Few placebo-controlled studies have examined the effect of allergen specific immunotherapy (SIT) on early and late phase asthmatic reactions. In this placebo-controlled study we have investigated the effect of 1 year of SIT with standardized birch pollen extract on early and late phase asthmatic reactions in adult asthmatic patients. METHODS: Nineteen patients with a history of birch-pollen-induced seasonal symptoms from upper and lower airways, positive skin prick test and in vitro specific immunoglobulin E to birch pollen extract were included. Allergen and methacholine bronchial challenges were performed and blood samples obtained for analyses of total eosinophil count and eosinophil cationic protein (ECP) in serum, before and after 1 year of immunotherapy treatment. RESULTS: All patients developed early and 16 of 19 both early and late phase asthmatic reactions. A significant increase in allergen dose was required to evoke early asthmatic reaction in the immunotherapy group (P < 0.01) after 1 year of treatment. The difference between the groups was significant (P < 0.01). Also the size of late asthmatic reaction was significantly reduced in the SIT group compared with placebo treated patients (P < 0.01). Twenty-four hours after allergen challenge methacholine sensitivity, number of total eosinophils and ECP increased significantly in the placebo (P < 0.02, P < 0.05 and P < 0.05 respectively), but not in the SIT group. CONCLUSION: Allergen SIT with standardized birch pollen extract decreased early and late asthmatic responses following bronchial challenge in pollen allergic patients, thus confirming anti-inflammatory effect of the treatment.