Separation of cysteine proteinase inhibitors from psoriatic scale.

Inhibitors of cysteine proteinases from extracts of psoriatic scales and from scrapings of normal skin surface were separated by using immunochemical, electrophoretic and chromatographic methods. The total inhibitory capacity of cysteine proteinases measured as inhibition of papain, was higher in the extracts from psoriatic scales than from normal skin surface scrapings. In normal skin samples only one inhibitor, acidic inhibitor, was identified while altogether three separate inhibitors were revealed in psoriatic extracts: an acid inhibitor (ACPI) with pI at 4 . 7-5 . 5, molecular weight around 12,000, a near-neutral inhibitor (NCPI) with pI at 6 . 0-6 . 5, molecular weight around 12,000, and a slightly alkaline inhibitor with pI around 7 . 0-7 . 5 and molecular weight 37,000. Two to three isoelectric variants were found in all these inhibitors. Quantitatively, the acid inhibitor is the most abundant one. The low molecular weight inhibitors (ACPI and NCPI) were localized with PAP method in the upper spinous cell layers in formalin-fixed skin sections. The slightly alkaline inhibitor with mol.wt 37,000 reacted in immunodiffusion with a commercial rabbit polyvalent antiserum. The abundance of cysteine proteinase inhibitors in the psoriatic lesion is considered as a local effort to compensate for the high cysteine proteinase activity.