Fel d 1 allergen protein complex (Fel d 1)

Fel d 1 is the principal allergenic protein complex produced by domestic cats (Felis catus), classified as a glycosylated secretoglobin of approximately 35–39 kDa that forms a tetrameric structure composed of two heterodimers, each consisting of chain 1 (8 kDa, ~70 amino acids) and chain 2 (10 kDa, ~90–92 amino acids), covalently linked via disulfide bonds[1][3][5][7]. Synthesized mainly in sebaceous and salivary glands, Fel d 1 is distributed throughout cat fur and dander during grooming, subsequently becoming airborne and adhering strongly to environmental surfaces, contributing to its status as the primary cause of cat allergy in humans[1][4][8]. It elicits IgE-mediated hypersensitivity (allergic rhinitis, asthma) in sensitized individuals, accounting for the majority of human cat allergies[1][3][8]. The precise biological function of Fel d 1 in felines remains unknown, though it shares structural similarity with uteroglobins and may be involved in ligand binding or immune modulation[2][3][7]. Targeting Fel d 1 by reduction of environmental levels, neutralization with specific antibodies, or immune desensitization forms the basis for investigational and experimental allergy therapies[3][8].

Other names

Major cat allergenCat secretoglobinCat allergen 1Cat uteroglobin-like proteinFelis domesticus allergen 1

Neutralizing antibodies sequester Fel d 1 to prevent IgE binding; Immunotherapy induces blocking IgG or alters T cell responses against Fel d 1