OLIGONUCLEOTIDE TYPING REVEALS ASSOCIATION OF TYPE-I PSORIASIS WITH THE HLA-DRB1-ASTERISK-0701 2, HLA-DQA1-ASTERISK-0201, HLA-DQB1-ASTERISK-0303 EXTENDED HAPLOTYPE/

Although the pathogenesis of psoriasis is still a matter of debate, th ere are several lines of evidence supporting the concept of this disea se being immunologically mediated with T cells playing a crucial role. Because a considerable portion of the cellular infiltrate in psoriasi s consists of activated T-helper cells, expression of HLA class II ant igens might be of particular importance for the understanding of its p athogenesis. Therefore, we investigated the HLA type of patients with type I (early onset, positive family history) and type II (late onset, no family history) psoriasis by means of serology (n = 89) and genoty ping using sequence-specific oligonucleotide probes (n = 64). Serologi c analysis of class I documented the association of type I psoriasis w ith HLA-Cw6, -B13, and -B57, whereas type II psoriasis showed a weaker correlation with HLA-Cw2 and -B27. Genotyping using SSO for class II detected the elevation of the HLA-DRB10701/2 allele frequency from 13 % in normal population to 36% in type I, but only to 15% in type II ps oriatics. Moreover, positive correlations with type I psoriasis were d etected for HLA-DQA10201 and HLA-DQB1*0303. The HLA-DRB1*0701/2, -DQA 10201, -DQB1*0303 extended haplotype was found exclusively in type I psoriasis. This is the first report documenting the association of dis tinct HLA class II alleles with type I psoriasis as detected on the DN A level, an approach both more specific and more sensitive when compar ed to serology.