The 43 kDa papain inhibitor in normal and diseased skin

The presence of 43 kDa papain inhibitor in 43 different skin diseases was immunohistochemically studied by using both poly- and monoclonal antibodies. Psoriasis and various eczematoid reactions as well as viral infections showed the most pronounced staining in the squamous cells of the epidermis. The antigen was also present in benign tumours or precancerous lesions which showed keratinization. Cells of poorly differentiated squamous cell carcinomas, basal cell carcinomas and melanocytic tumours were negative. The antigen seems to be related to disturbed keratinization and benign proliferation in non-neoplastic dermatoses and it is also present in differentiating squamous neoplasms.