Persistent specific bronchial reactivity to occupational agents in workerswith normal nonspecific bronchial reactivity

Specific bronchial reactivity (SBR) to common inhalants is related to the d egree of nonspecific bronchial reactivity (NSBR) and to specific allergen s ensitivity. We investigated 16 workers with normal NSBR who had been previo usly diagnosed with occupational asthma caused by high-molecular-weight age nts. The agents were flour in seven workers, psyllium in five, and guar gum in four. The subjects had been removed from exposure to these agents for a mean of 5.7 (+/- 4.0 SD) yr, no longer showed evidence of persisting asthm a, and had a normal lung function. In the present study, the workers were r eexposed to the sensitizing agent by specific inhalation challenges, in the same way they were as at the time of the diagnosis, to assess their curren t SBR to the sensitizer. SBR was estimated as the duration of exposure that induced a 20% decrease In FEV,. Eleven of the 16 subjects had an asthmatic reaction at the time of the study; the duration of exposure necessary to i nduce the asthmatic reaction was the same as that needed at the time of dia gnosis (3.55 +/- 0.5 min and 4.2 +/- 0.7 min, respectively, p = 0.8). The d ecrease in specific IgE levels between the two events was much greater in t he subjects who failed to react to the second challenge test (from 24.2 +/- 37.5% to 3.0 +/- 16.9% binding) than in those who reacted on both occasion s (from 31.2 +/- 27.0% to 21.6 +/- 36.7% binding); however, in both groups the change was significant (p = 0.05 and 0.04 respectively). We conclude th at SBR to high-molecular-weight agents persists in most cases despite a nor malization of NSBR, and that this persistence is associated with a persiste nce of specific immunization to the agent.