HLA-DRB1*0701 and DRB1*1401 are associated with genetic susceptibility to psoriasis vulgaris in a Taiwanese population

We analysed the allelic frequencies of class II human leucocyte antigen (HLA)-DRB1, DQA1, DQB1 and DPB1 by polymerase chain reaction/sequence-specific oligonucleotide probe hybridization typing in 76 Taiwanese psoriasis vulgaris (PSV) patients and 238 Taiwanese non-psoriatic controls. The analysis revealed the following: (i) the DRB1*0701 allele was positively associated with PSV (relative risk. RR = 6.4, corrected P-value, Pc less than or equal to 0.001); (ii) the DRB1*1401 allele was positively associated with type I PSV (age at onset < 40 years) (RR = 3.5, Pc less than or equal to 0.001); (iii) the DQA1*0501 allele was negatively associated with PSV (RR = 0.4, Pc less than or equal to 0.001); (iv) there was no significant association of HLA-DP genes with PSV; and (v) there was a strong association of beta-chain phenylalanine at position 37 (Phe 37) and glutamate or glutamine at position 74 (Glu 74/Gln 74) with PSV (RR = 3.5, Pc less than or equal to 0.001 for the association of Phe 37 with PSV; RR = 2.2, Pc less than or equal to 0.001 for the association of Glu 74/Gln 74 with PSV). The positive association between PSV and the DRBI*0701 allele is consistent with previous reports, The negative association of the DQA1*0501 allele is reported only in Finland, whereas the positive association between PSV and the DRB1*1401 allele has never been described before. Trans-racial studies may shed further light on the association of class IT HLA alleles or other closely linked genes with the development of PSR Phe 37 (a large, nonpolar amino acid) and Glu 74/Gln 74 (both negatively charged amino acids) were the polymorphic residues in pockets 9 and 4. respectively, of the beta-chain, which may have increased their affinity for the small non-polar amino acids and basic amino acids of the psoriatic antigen peptide, thereby activating the T lymphocytes. This finding may facilitate the identification of a psoriatic antigen.