Polymorphism in transporter antigen peptides gene (TAP1) associated with atopy in Tunisians.

BACKGROUND

Transporter antigen peptide 1 (TAP1) and TAP2 gene products from a transporter molecule involved in antigen presentation. Polymorphic residues have been described in both genes and could have functional consequences in the immune response.

OBJECTIVE

We designed a case-control study to investigate the potential association of polymorphism of the TAP1 gene with atopy.

METHODS

We used the amplification refractory mutation system polymerase chain reaction to characterize TAP1 gene polymorphism in 84 unrelated Tunisian patients with atopy and 81 healthy control subjects.

RESULTS

Analysis of TAP1 polymorphism in Tunisian patients with atopy and in unaffected control subjects demonstrates a high relative risk (RR) of atopy in carriers of a codon (d) corresponding to a glycine at position 637 of the TAP1-B and TAP1-D alleles. The relative risk of allergic asthma is markedly higher in homozygotes (d/d) (RR = 22; p < or = 0.0001). The TAP1-D allele, not observed in European populations, has a frequency of 5% in the Tunisian control subject group. 4 major increase of the frequency (f) of the D allele is observed in patients with allergic asthma (f = 35%) and in those with allergic rhinitis (f = 22%), indicating a high relative risk of allergic asthma (RR = 10.2; p < 0.0001) and of allergic rhinitis (RR = 5.4; p < or = 0.005) in individuals carrying this allele. DD homozygotes were found only among patients with allergic asthma (23% of patients with asthma). Further evidence of the strong association between TAP1 polymorphism and atopy was provided by the finding that atopy is transmitted by inheritance of the glycine-637 marker.

CONCLUSIONS

Tunisian persons carrying the glycine-637 of the TAP1 protein may have an increased risk of atopy. Specific association was found between the homozygous TAP1 D/D genotype and allergic asthma.