Low level antigen responses in guinea-pig lung strip

Guinea-pigs were sensitized either by i.p. administration or by a novel procedure involving inhalation of ovalbumin (2, 0.2 and 0.002%) on days 0, 5 and 19 respectively. Lung strips from these guinea-pigs were challenged with both low (0.02 micrograms/ml) and high (10 micrograms/ml) concentrations of ovalbumin and the responses compared. Whereas the low level antigen gave consistent contractions following aerosol sensitization, no response was observed from the i.p. sensitized guinea-pig lung strips. Marked differences were also observed following the high ovalbumin challenge, where the aerosol sensitized lungs gave almost twice the response as tissue from the i.p. sensitized guinea-pigs, the former being approximately 140% of that observed with acetyl-beta-methyl choline (1 mM). Furthermore, the response elicited in the lungs from aerosol sensitized guinea-pigs were not modified by the addition of high concentrations of the H1-antagonist diphenhydramine (100 microM), before or subsequent to challenge. The data suggest that the aerosol sensitization procedure gives rise to a contractile response in guinea-pig lung strips which contains no observable histamine component.