ALLERGENS OF MAMMALIAN ORIGIN .5. PROPERTIES OF EXTRACTS DERIVED FROM DOMESTIC CAT

Eight commercial cat dander extracts and 2 pelt extracts derived from mongrel and Siamese cats were compared. Cat allergen 1 and cat albumin were measured by radial immunodiffusion. Allergenic activity was evaluated by [human] prick test and a modified radioallergosorbent test [RAST]. In the latter, the dilution of each extract that produced 50% inhibition of binding of IgE [immunoglobulin E] antibodies to insolubilized cat allergen 1 (RAST 1) and insolubilized cat serum (RAST 2) was determined. The total non-dialyzable solid content of the extracts did not correlate with any other parameter. Cat allergen 1 content determined by radial immunodiffusion correlated with average prick test results in 10 cat-sensitive subjects and with RAST 1 activity. Cat albumin content correlated weakly with RAST 2 activity, but not with any other measure of allergenic activity. Absorption of each extract with the .gamma.-globulin fraction of rabbit antiserum to cat allergen 1 significantly reduced prick test reactivity and RAST 1 activity, but not RAST 2 activity. Cat allergen 1 is apparently an important allergen in cat dander extracts; its measurement may be used to standardize the allergenic activity of such extracts.