Felis domesticus allergen extract

Felis domesticus allergen extract is a complex biological mixture of proteins derived from the hair, dander, and saliva of the domestic cat, used primarily for the diagnosis and treatment of feline-related allergic diseases. The extract consists of several distinct molecular components, most notably Fel d 1, a secretoglobin that is the primary driver of allergic sensitization in over 90% of cat-allergic individuals. Other components include Fel d 2 (serum albumin), Fel d 3 (cystatin), and several lipocalins such as Fel d 4. In sensitive patients, these allergens cross-link IgE antibodies on the surface of mast cells and basophils, triggering the release of inflammatory mediators like histamine that cause allergic rhinitis and asthma symptoms. Therapeutically, the extract is used in allergen-specific immunotherapy (AIT) to desensitize the patient's immune system by shifting the T-cell response from a Th2 allergic profile toward a protective Th1 or T-regulatory (Treg) profile and inducing IgG4 blocking antibodies. Modern pharmacological approaches also include the development of recombinant single-allergen vaccines and monoclonal antibodies that specifically target or neutralize the Fel d 1 protein to improve efficacy and reduce systemic side effects.

Other names

Cat hair allergenic extractCat dander extractFelis catus allergenic extractStandardized cat hair extractCat allergen extract

Allergen-specific immunotherapy (AIT) functions by inducing immune tolerance via the repeated administration of increasing doses of the extract, leading to a shift from Th2 to Th1/Treg responses, production of allergen-specific IgG4 blocking antibodies, and suppression of IgE-mediated degranulation; additionally, monoclonal antibodies target specific allergen components like Fel d 1 or sequester IgE to prevent the allergic cascade.