IGG1-MEDIATED ACUTE PULMONARY HYPERSENSITIVITY RESPONSE IN THE GUINEA-PIG - INVOLVEMENT OF SPECIFIC LIPID MEDIATORS

We determined the pulmonary obstructive response to aerosolized antigen challenge, and its sensitivity to antagonists of specific lipid mediators, in IgG1 passively sensitized (IgG1-PS) guinea pigs. Antiovalbumin (OA)-IgG1 was isolated by affinity chromatography from serum derived from actively immunized Hartley guinea pigs. Propranolol and pyrilamine pretreated, IgG1-PS guinea pigs were challenged with aerosolized antigen and pulmonary obstruction was quantified by measurements of excised lung gas volume (ELGV). ELGV increased between 150 and 1,035% in a dose-proportional fashion with increasing antigen exposure (0.001 to 0.1% nebulizer concentration). The leukotriene antagonists ICI-204,219 and SKF-104,353 exhibited dose-proportional inhibitions in antigen-induced elevations in ELGV, inhibiting up to 65 and 87% at the maximal concentrations examined. Similarly, the platelet-activating factor (PAF) antagonists WEB-2086 and L-659,989 inhibited antigen-induced elevations in ELGV, inhibiting up to 94 and 59% at the maximal concentrations examined. In contrast, the cyclooxygenase (CO) inhibitor piroxicam significantly enhanced (p < 0.05) the OA-induced elevations in ELGV. Aerosolized PAF challenge produced dose-proportional elevations in ELGV that were significantly inhibited by the LTD4 antagonist ICI-204,219 (38 and 43% inhibition) and the CO inhibitor piroxicam (62 and 48% inhibition) in sensitized and nonsensitized animals, respectively. We hypothesize that IgG1-dependent airway obstruction is mediated in part by LTD4 produced in response to PAF generation.