Psoriasis is a multifactorial autoimmune skin disease with a pathogenesis that has remained obscure. Recently, T cells bearing natural killer receptors (NKRs) were precisely and strongly targeted as new putative pathogenic immunocytes in psoriasis. Among NKRs, killer cell immunoglobulin-like receptor (KIR) is the major molecule recognizing HLA class I allotypes and might be closely related to psoriasis.

To investigate the association of KIR genotype and patients with psoriasis in Korean, we defined the 14 KIR genotypes in 96 patients with psoriasis and 86 healthy controls using PCR-SSP methods.

The frequencies of KIR2DS4 and KIR3DL1 were significantly decreased in psoriasis compared with controls (RR=0.21, p<0.02). When patients were divided into two subgroups at the age of onset, type I (<30 years) and type II (≥30 years) respectively, these phenomena were similarly observed independent of groups divided (type I: RR=0.26, p<0.005; type II: RR=0.14, p<0.0006). When the patients were divided into subgroups according to the age of onset and family history, the frequencies of KIR2DS4, KIR3DL1, and KIR2DS3 were significantly decreased in type I compared with type II psoriasis (3DL1, 2DS4: p<0.004; 2DS3: p<0.04) and were significantly decreased in psoriasis without family history compared to with family history (3DL1, 2DS4: p<0.007; 2DS3: p<0.05). The frequency of haplotype combination BB was significantly increased in psoriasis compared with controls (RR=2.74, p<0.009).

These results suggest that KIR genotype is a factor for the occurrence and development of psoriasis and in future how combinations of HLA and KIR genes influence psoriasis needs to be defined.