The immediate and late allergic response to segmental bronchopulmonary provocation in asthma

The response to antigen is an important factor in the development of airway inflammation. Segmental bronchoprovocation (SEP) with antigen and subsequent bronchoalveolar lavage (BAL) have provided valuable insight into the mechanisms of allergic inflammation. To determine the features of allergic airway response in asthma, 19 subjects with mild asthma underwent antigen SEP in a dose-dependent manner. The amount of antigen used in SEP was 0 (saline), and 1, 5, or 20% of the antigen dose required to drop the FEV1 by 20% (APD(20)). BAL was done at 5 min and 48 h after SEP. BAL histamine levels increased modestly 5 min after antigen SEP. At 48 h, there was a marked increase in eosinophils and IL-5 concentration even in airway segments where the release of histamine was smart. Moreover, eosinophils correlated with IL-5 levels at 48 h (r = 0.63; p < 0.001), but not with BAL histamine concentrations at 5 min. CM-CSF levels did not increase after antigen SEP and did not correlate with eosinophils. These observations indicate that asthmatic subjects can develop a dose-dependent response to antigen SEP that is characterized by a modest increase in histamine immediately after antigen exposure, and marked eosinophilia, which appears proportionately greater than the histamine response and relatively greater than what is seen in allergic nonasthmatic subjects. This feature might be important to the eventual development of airway inflammation in asthma.