Decreased levels of IL-1 alpha and beta in psoriatic lesional skin.

Interleukin 1 (IL-1), which mediates a wide range of biological activities, is thought to play an important role in many inflammatory and immunologic diseases. Normal human epidermal keratinocytes constitutively produce IL-1. Based on our previous data indicating decreased IL-1 activity in psoriatic scale extracts, in the present study, we measured immunoreactive IL-1 alpha and beta levels in the suction blister fluids as well as in the psoriatic scale extracts using enzyme immunoassay for IL-1 alpha and beta. The results showed that although similarly low levels of IL-1 alpha were detectable in the suction blister fluid from normal and psoriatic lesional skin, and that no IL-1 beta was found in most of the blister fluids, indicating that IL-1 alpha is major IL-1 species produced by human skin. As compared to those in the blister fluids, IL-1 alpha levels in the horny tissue extracts were found to be much higher, and they were significantly higher in the orthokeratotic stratum corneum extracts than in the psoriatic scale extracts. However, gel filtration of the orthokeratotic horny tissue extracts demonstrated that constituents for immunoreactive IL-1 alpha and beta were quite variable depending upon the source of the horny tissues. The present study has confirmed that IL-1 levels in the psoriatic scale extracts are decreased when compared with those in the orthokeratotic horny tissue possibly due to an increased epidermal proliferation activity associated with its high turnover rate. The role of IL-1 psoriatic lesions remains unknown.