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Clin Exp Allergy. 2004 Nov;34(11):1732-8.

Fel d 4, a cat lipocalin allergen.

Author information

1
Telethon Institute for Child Health Research and Centre for Child Health Research, University of Western Australia, West Perth, WA, Australia. wendy@ichr.uwa.edu.au

Abstract

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.

[Indexed for MEDLINE]

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