Fel d 4, a cat lipocalin allergen

Clin Exp Allergy. 2004 Nov;34(11):1732-8. doi: 10.1111/j.1365-2222.2004.02090.x.


Background: Cat allergy is unique among allergy to mammals in that the major allergen Fel d 1 is a uteroglobin-like protein and not a lipocalin. The biochemical spectrum of the cat allergens is thus uncertain, particularly with regard to the role that a cat lipocalin protein may play in sensitization to cats in allergic individuals.

Objective: To analyse cDNA encoding a lipocalin allergen and the corresponding recombinant allergen at both the molecular and immunological levels.

Methods: A submandibular salivary gland cDNA expression library was constructed and screened for clones producing IgE-binding polypeptides. cDNA encoding a lipocalin allergen and its corresponding recombinant allergen were analysed.

Results: An IgE binding molecule with high sequence identity to the boar salivary lipocalin and the horse lipocalin Equ c 1 allergen was isolated and designated, Fel d 4. Serum from 62.96% of cat-allergic subjects examined had measurable IgE antibody to Fel d 4 but typically at low levels. Despite this in 47% of sera the anti-Fel d 4 IgE titres were higher than the anti-Fel d 1 titres. IgE binding to the lipocalin allergen could be blocked by an allergen extract from cow and to a lesser degree by extracts from horse and dog.

Conclusion: Fel d 4 is a lipocalin allergen produced by the cat, which binds IgE at relatively high frequency in cat-sensitive individuals. The allergen provides not only a means for investigating differences in the immune response to lipocalin allergens from that found for other mammalian species but also an important reagent for the diagnosis of cat allergy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allergens / chemistry
  • Allergens / genetics*
  • Allergens / immunology
  • Amino Acid Sequence
  • Animals
  • Binding, Competitive
  • Cats / immunology*
  • Cross Reactions
  • DNA, Complementary / genetics
  • Gene Library
  • Glycoproteins / chemistry
  • Glycoproteins / genetics*
  • Glycoproteins / immunology
  • Humans
  • Hypersensitivity, Immediate / etiology
  • Hypersensitivity, Immediate / immunology*
  • Immunoglobulin E / biosynthesis
  • Lipocalins
  • Mammals / immunology
  • Models, Molecular
  • Molecular Sequence Data
  • Recombinant Proteins / immunology
  • Sequence Alignment
  • Species Specificity


  • Allergens
  • DNA, Complementary
  • Fel d 4 allergen, Felis domesticus
  • Glycoproteins
  • Lipocalins
  • Recombinant Proteins
  • Immunoglobulin E
  • Fel d 1 protein, Felis domesticus