High prevalence of sensitization to cat allergen among Japanese children with asthma, living without cats.
BACKGROUND
Cat allergy is common among children with asthma. Many cat-allergic patients in Japan and elsewhere do not keep cats, but nonetheless become sensitized through environmental exposure to cat allergen.


OBJECTIVE
To assess the frequency of cat allergy and cat-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) antibody responses in young Japanese patients with asthma in relation to self-reported cat exposure and Fel d 1 levels in dust samples.


METHODS
Cat dander-specific IgE antibody was measured in sera from asthma patients using the CAP system. IgE and IgG antibody to Fel d 1 was measured by antigen binding radioimmunoassay and by chimeric enzyme immunoassay. Fel d 1 levels in dust samples from a subset of patients' homes were measured by monoclonal antibody-based enzyme immunoassay.


RESULTS
Cat-specific IgE (CAP class>/=2) was found in sera from 70% of 44 patients who kept cats and 34% of 394 patients who had never kept cats. The prevalence of sensitization increased progressively to age 6 years (40%: positive), and then increased gradually to age 16 years (approximately 60%: positive) in patients who had never kept cats. There was an excellent correlation between cat CAP values and IgE levels to Fel d 1. The absolute amount of IgE antibody to Fel d 1 ranged from 0.01 to 15.6% of total IgE. Most patients who did not keep cats were exposed to Fel d 1 levels ranging from 0.07-8 microg/g dust.


CONCLUSIONS
Sensitization to cat allergen is common among young asthmatic patients in Japan, even among patients who do not keep cats. Use of CAP and the chimeric enzyme-linked immunosorbent assay allows accurate diagnosis of cat allergy and quantification of specific IgE antibody levels.
Ichikawa
K
K
Department of Pediatrics, Doai Memorial Hospital, Sumida-ku, Tokyo, Japan.
Iwasaki
E
E
Baba
M
M
Chapman
M D
MD
D000293:Adolescent; D000328:Adult; D000818:Animals; D000829:Animals, Domestic; D000906:Antibodies / Q000032:analysis / Q000276:immunology; D001249:Asthma / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D004391:Dust / Q000032:analysis; D005260:Female; D006023:Glycoproteins / Q000032:analysis / Q000276:immunology*; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology* / Q000276:immunology*; D007073:Immunoglobulin E / Q000032:analysis / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis / Q000276:immunology; D007223:Infant; D007564:Japan; D008297:Male; D015995:Prevalence
D000906:Antibodies; D004391:Dust; D006023:Glycoproteins; D007074:Immunoglobulin G; D007073:Immunoglobulin E; C059296:Fel d 1 protein, Felis domesticus