Allergy to rats: quantitative immunoelectrophoretic studies of rat dust as a source of inhalant allergen

The antigenic composition of an extract of rat dust, as a source of aeroallergens for rat-sensitive individuals, has been investigated and compared to the antigenic composition of rat saliva and urine. Of four main antigenic peaks identified by crossed immunoelectrophoresis, one antigenic peak (Ag 4) was demonstrated to be antigenically closely related to and with similar molecular weight (approximately 22 kd) and isoelectric point values as urinary prealbumin, already recognized as a major rat allergen. Ag 4 was present in all dusts studied and was also identified as a minor component of saliva. However, no component with the same electrophoretic mobility or physicochemical characteristics of the alpha 2-euglobulin of male rat urine that shares partial identity with the prealbumin was detected, even in dust collected from a male rat room. A second high molecular weight (greater than 200 kd) component, Ag 1, present in most of the dust extracts, could not be detected in either urine or saliva. Crossed immunoelectrophoresis and skin prick tests confirmed the allergenicity of both these antigens. Analysis of an air filter sample taken within a male rat room revealed significant amounts of the "prealbumin" component, and a monospecific antiserum to this component was used to quantitate levels in dusts collected from various locations. These findings suggest that a major inhalant allergen present in rat dust is closely related to urinary prealbumin but that this and other allergenic components may not be derived predominantly from rat urine or saliva but possibly from secretions originating from the skin of the animals and present in the fur.