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 (HL A)-DRB1, DQA1, DQB1 and DPB1 by polymerase chain reaction/sequence-specific oligonucleotide probe hybridization typing in 76 Taiwanese psoriasis vulga ris (PSV) patients and 238 Taiwanese non-psoriatic controls. The analysis r evealed the following: (i) the DRB1*0701 allele was positively associated w ith 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 positi on 74 (Glu 74/Gln 74) with PSV (RR = 3.5, Pc less than or equal to 0.001 fo r 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 associatio n between PSV and the DRBI*0701 allele is consistent with previous reports, The negative association of the DQA1*0501 allele is reported only in Finla nd, whereas the positive association between PSV and the DRB1*1401 allele h as never been described before. Trans-racial studies may shed further light on the association of class IT HLA alleles or other closely linked genes w ith 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 increa sed their affinity for the small non-polar amino acids and basic amino acid s of the psoriatic antigen peptide, thereby activating the T lymphocytes. T his finding may facilitate the identification of a psoriatic antigen.