Low doses of animal antigen attenuates the late asthmatic reaction

Five subjects with a history of asthma after exposure to cat or dog underwent a trial of low-dose antigen injection followed by bronchoprovocation with the relevant antigen. The neutralization dose of antigen was determined by serial and point dilution skin testing. In a crossover protocol, patients received this antigen or placebo injections. They then underwent bronchoprovocation with the same antigen. The results of the early and late reaction to bronchoprovocation were compared, with each patient serving as her own control. As measured by the number of breath units to lower the FEV1 by 20%, placebo group tolerated only 6.9 +/- 2 breath units, whereas the neutralization group tolerated 29 +/- 3 breath units (p less than 0.05). The maximum decline in FEV1 during the late reaction was 27 +/- 13% after injection of placebo and 12 +/- 12% after injection of antigen (p less than 0.05). In this model of antigen-induced asthma, injection of low doses of allergen immediately preceding bronchoprovocation blunted the immediate and delayed asthmatic reaction.