Airway allergy to trimellitic anhydride in guinea pigs: Different time courses of IgG 1 titer and airway responses to allergen challenge

Abstract

Background: Trimellitic anhydride (TMA) is a low molecular weight chemical that may cause occupational asthma in human beings. The objectives of this study were to determine the time course of immune and airway responses to TMA in guinea pigs and to relate the immunologic response to the immediate responses in lung resistance (R L) and plasma exudation induced by allergen challenge. Methods: We studied the effects of time course after sensitization on airway response to TMA in guinea pigs actively sensitized to free TMA, given by intradermal injection (0.1 ml of 0.3% TMA in com oil). During weeks 1, 2, 3, 5, and 8 after sensitization, anesthetized animals were challenged with TMA conjugated to guinea pig serum albumin (TMA-GPSA), instilled via the airway route. Nonsensitized animals were challenged with the same amount of conjugate 4 weeks after intradermal injection of corn oil only. In the same animal, we measured both R L to monitor airflow obstruction and extravasation of Evans blue dye (20 mg/kg) to quantify airway plasma exudation. Results: Instillation of TMA-GPSA (0.5%; 50 μl) into the tracheal lumen caused a significant increase in R L, reaching a maximum at 2.5 minutes after the instillation in the 1-week group (9.0 ± 5.9 cm H 2O/ml/sec) and between 5 and 6 minutes in the 2-, 3-, 5-, and 8-week groups (9.4 ± 4.8, 12.7 ± 5.5, 3.7 ± 1.1, and 1.7 ± 0.2 cm H 2O/ml/sec, respectively). The maximal increase in R L after the challenge in nonsensitized animals was 0.39 ± 0.05 cm H 2O/ml/sec. TMA-GPSA also produced significant extravasation of Evans blue dye at all airway levels in the senzitized groups, and the amount of dye in the peripheral airways was significantly greater than that in the trachea. Furthermore, the level of Evans blue dye in airway tissue increased with the time after sensitization, up to the latest time point tested (8 weeks). Specific IgG 1 antibodies to TMA-GPSA demonstrated by ELISA were detected in all animals in the 3-, 5-, and 8-week groups, with maximal levels 5 weeks after sensitization. Specific IgG 1 titers to TMA-GPSA significantly correlated with the level of Evans blue dye induced by challenge with TMA-GPSA but not with the increase in R L. Conclusions: Intradermal sensitization to free TMA induces specific airway allergy for a long period after sensitization. Specific IgG 1 antibodies to allergen may influence allergen-induced plasma exudation rather than the airflow obstruction in this animal model of TMA-induced asthma.