Role of purified IgG1 in pulmonary hypersensitivity responses of the guinea pig.

Guinea pigs have been used extensively to model pulmonary hypersensitivity responses. Although guinea pigs produce mainly immunoglobulin G1 (IgG1) antibodies and humans produce IgE, both immunoglobulin classes have been shown to be regulated similarly. We used an established guinea pig model to examine the role of IgG1 in immediate- and late-onset pulmonary hypersensitivity responses. IgG1 was purified from the serum of ovalbumin-immunized animals and shown to be free of IgE. It was transferred into naive recipients in doses quantified on the basis of its biological activity as measured in the passive cutaneous anaphylaxis (PCA) assay. Inhalation challenge of recipient animals 24 h later with an ovalbumin aerosol produced immediate-onset airway constrictive responses, with response dependent upon the quantity of antibody passively administered. None of the recipient animals displayed a late-phase response previously shown to be characterized by increased breathing frequency, airflow limitation during exhalation, and mild fever. However, pulmonary eosinophilia, measured at 24 h postinhalation challenge, was detected with the severity of the eosinophilia dependent upon the quantity of IgG1 administered. The results indicated that immediate-, but not late-onset, responses were associated with IgG1 antibody. Occurrence of late-onset pulmonary eosinophilia indicated that eosinophilic inflammation, a recognized characteristic of hypersensitivity responses, was related to antigen-specific IgG1 antibody.