Antigen-specific IgE and IgA antibodies in bronchoalveolar lavage fluid are associated with stronger antigen-induced late phase reactions

Background The mechanism(s) leading to the development of late phase allerg ic reactions is (are) unknown. Previous studies have indicated that a relat ionship between serum IgE and the late phase exists. Objective To explore the relationships between allergen-specific immunoglob ulins in bronchoalveolar lavage (BAL) fluids and the magnitude of airflow l imitation during the late phase response to inhaled allergen. Methods Ragweed-specific IgE, IgA, secretory IgA (sIgA) and IgG were measur ed in BAL fluid and in the serum 1-5 weeks before whole lung antigen challe nge with ragweed extract, in 16 ragweed allergic asthmatics. In addition, B AL and serum eosinophil cationic protein (ECP) and BAL fibrinogen levels we re determined and BAL cells counted and differentiated. The latter procedur es were repeated in a second BAL performed 24 h after the end of the ragwee d challenge. After the challenge, lung function was monitored hourly for 8 h, to record the magnitude of airflow limitation. Results Ragweed-specific immunoglobulins were detected in 25% to 37.5% of B AL samples. Compared to the subjects with undetectable BAL fluid ragweed-sp ecific IgE levels at baseline, those with detectable antibodies had stronge r late phase reactions as determined by the nadir of FEV1 between hours 4 a nd 8 after the ragweed inhalation challenge (P = 0.0007). Allergen-induced changes in BAL ECP and fibrinogen levels were also higher in those subjects with detectable ragweed-specific IgE in baseline fluids (P = 0.03 and P = 0.005, respectively). Significant relationships between BAL antigen-specifi c IgA, serum ragweed-specific IgE and IgA and the late phase reaction were also found. Conclusion The results of this study point towards the possibility that all ergen-specific IgE and IgA may be independently involved in the pathogenesi s of the late phase reaction. This notion merits further exploration.