RELATIONSHIP BETWEEN IGG1 LEVELS AND AIRWAY RESPONSES IN GUINEA-PIGS ACTIVELY AND PASSIVELY SENSITIZED TO HEXAHYDROPHTHALIC ANHYDRIDE

Organic acid anhydrides (OAAs) are industrial chemicals that may cause induction of specific IgE and airway symptoms in exposed workers, The y are a good model for studies of relationships between chemical struc ture and the sensitizing potential of reactive low-molecular-weight co mpounds. Hexahydrophthalic anhydride (HHPA) is such a compound. This s tudy aimed to evaluate the relationship between specific IgG1 levels a nd airway responses in a model to predict the sensitizing potential of OAAs. Guinea pigs were either actively or passively sensitized to HHP A, For active sensitization. guinea pigs were injected i.d. with 0.1 m l of olive oil (vehicle) or 0.05, 0.5, or 5% HHPA in olive oil. Passiv e sensitization was performed by i.p. injection of different volumes o f antisera (0.75-6 ml, either unheated to keep IgE or heated to destro y IgE) taken from HHPA-sensitized guinea pigs. Specific antibody level s were evaluated with ELISA and passive cutaneous anaphylaxis. Animals were challenged 16-18 days after active sensitization, or 2 days afte r passive sensitization. by intratracheal instillation with HHPA conju gated to guinea pig serum albumin (HHPA-GPSA; 0.05% in saline), and th e immediate effects on lung resistance (R-L), and plasma extravasation . measured as Evans blue dye extravasation, for up to 6 min were recor ded. Active sensitization caused production of specific IgG1. Provocat ion with HHPA-GPSA caused an increase of both R-L and Evans blue dye e xtravasation. which was dependent upon the active sensitization dose. Challenge with HHPA-GPSA in passively sensitized guinea pigs also prod uced an:increase in both R-L and Evans blue dye extravasation which wa s related to the IgG1 level. In the guinea pig model of HHPA-induced a irway allergy, the airway resposes are closely related to the serum le vels of specific IgG1. Thus. the IgG1 levels induced by the immunizati on may reflect the sensitizing potential of HHPA.