Study on the expression of IL-18, AcPL and IL-18BP mRNA in the psoriatic lesions

To investigate the role of IL-18 and IL-18 binding protein (IL-18BP) in the pathogenesis of psoriasis, PT-PCR was used to semi-quantitatively analyze the mRNA expression of IL-18, AcPL (accessory protein-like) and IL-18BP in 12 psoriatic lesions and in 6 normal skin tissues. The results showed that IL-18 and AcPL mRNA were present in all specimens from 6 normal skin and 12 pieces of psoriatic skin, and IL-18 and AcPL showed relatively stronger intensity in the psoriatic skin compared with those seen in normal skin (P<0.01). Amplified bands indicating the expression of IL-18BP mRNA were weakly positive in all samples of normal skin. In contrast, the PCR products for IL-18BP were distinctly visible in all specimens of psoriatic lesions (P<0.01). These findings demonstrate that IL-18 is constitutively synthesized by human keratinocytes and involved in the development of the Th1 response in psoriatic lesions, and its bioactivity appears to be closely regulated by cutaneous inflammation.