Abstract
Studies were undertaken to examine the factors influencing the development of Type I respiratory allergy in the rat, with a view to providing an animal model for assessing the potential of inhaled materials to induce respiratory allergy. Differences between the Brown Norway (BN) and PVG rat strains in relation to their ability to produce reaginic antibody following inhalation exposure, and differences in lung cell populations following inhalation challenge, underlined the importance of genetic constitution of the selected experimental animal. Following pre-treatment with the adjuvant carrageenan it was possible to induce sustained reaginic antibody responses to inhaled ovalbumin in the BN rat, which could be re-elicited upon subsequent exposure. Inhalation challenge of sensitised animals produced a characteristic "notching" breathing pattern associated with respiratory sensitivity in the rat, which was considered indicative of a positive respiratory response. Aspects of atmosphere generation were investigated with regard to their influence on immune recognition. Several factors were found to influence the range of particle sizes generated, these included choice of generating system, nature and concentration of test material and use of diluting air. Intraperitoneal administration of material together with carrageenan was employed to assess the allergenicity of various low molecular weight materials, which were administered conjugated to either rat serum albumin or ovalbumin. Hexyl isocyanate, penicillin G and eight reactive dyes were assessed both in terms of induction of reaginic antibody and elicitation of respiratory responses during inhalation challenge using either BSA-conjugated or free material. Using this system differing allergenic potencies were revealed, which for the reactive dyes was related both to their ability to bind to protein and the hapten density of the dye-protein conjugates produced. In addition, the use of computer graphic molecular modelling of two reactive dyes showed some correlation between the chemical structure of the dyes and their allergenic potential.