STUDY OF ASPARTATE AT RESIDUE-9 OF HLA-C MOLECULES IN JAPANESE PATIENTS WITH PSORIASIS-VULGARIS

The frequency of aspartate at residue 9 (Asp-9) of HLA-C molecules was investigated among 75 Japanese patients with psoriasis vulgaris and 5 0 healthy controls. We developed a technique of polymerase chain react ion sequence-specific primer (PCR-SSP) amplification of genomic DNA fo r HLA-C alleles with a codon for Asp-9. The specificity of amplificati on was confirmed by direct sequencing of the amplified products and am plification from total RNA (RT-PCR). Asp-9 was positive in all individ uals with Cw6 and/or Cw7, but negative in the others, indicating that Asp-9 was specific to Cw6 and Cw7 antigens in our subjects. The freque ncy of Asp-9 was significantly increased in the patient group (48% vs. 20%; P < 0.002). The frequency of alanine at residue 73 (Ala-73), whi ch was positive for Cw4, Cw6, Cw7, and some C blanks, was also increas ed in our previous study (81% vs. 48%; P < 0.0001). Asp-9 is located o n a beta sheet of alpha 1 domain of HLA-C molecule and influences the peptide binding of the C pocket of the groove together with Ala-73. Bo th Asp-9 and Ala-73 could contribute to the disease susceptibility to psoriasis vulgaris in the immune responses.