Identification and clinical significance of allergenic molecules of cat origin. Part of the DAS 76 Study.

Freeze-dried extracts from cat dander and the corresponding rabbit antibodies were used for establishing the CIE reference pattern for cat dander extracts. Anti-Cat Ag 1 and anti-cat albumin were used for identification of the corresponding antigens. CRIE on sera from selected groups of American and Danish cat-allergic patients demonstrated antigen-specific IgE binding to 10 of 15 cat dander antigens (Cat Ag 1 being the major allergen). Only minor differences were found between the two groups. Four of these allergens were serum proteins. Variable amounts of many of the 10 allergens were measured by QIE in saliva, serum, urine and three cat pelt extracts. However, extremely wide ranges for content of the serum allergens and the non-serum allergens were found. This was exemplified by an albumin/cat Ag 1 ratio between 1 and 400, smallest in cat dander. Immunoabsorption using anti-cat dander, anti-cat albumin and anti-Cat Ag 1 indicated that the anti-cat dander, anti-cat albumin, and the anti-Cat Ag 1 absorbed approximately 90%, 25%, and 56%, respectively, of the dander RAST activity, and 87%, 11%, and 45%, respectively, of the saliva RAST activity, confirming the major importance of Ag 1. It is concluded that cat allergenic extracts should contain only modest amounts of serum albumin and other serum-derived antigens and that any relevant standardization must include quantification of at least Cat Ag 1 and cat albumin.