Isolation and characterization of cal allergens.

A crude (saline soluble) extract of cat skins capable of eliciting a strong positive prick skin test in cat sensitive individuals was fractionated on Sephadex G200. Active fractions were pooled and successively fractionated on isoelectric focusing gradients of pH 3-5 and pH 4-5. Allergenic activity was localized in two peaks with mean isoelectric points of 4-1 and 4-35 respectively. On immunoelectrophoresis the allergen with pI = 4-35 was associated with a protein which was subsequently found to be immunologically indistinguishable from serum albumin and to have a molecular weight of 69,000 daltons. The allergen with pI = 4-1 migrated in the alpha2-region on immunoelectrophoresis and had a mean molecular weight of 55,000 daltons. This allergen was isolated and analysed for amino acid and carbohydrate content. A combined extract of both allergens coupled to microcrystalline cellulose and used a RAST procedure readily distinguished between two groups of individuals classified as skin test positive and skin test negative to cat allergen.