HLA-DR-antigen bearing keratinocytes in various dermatologic disorders.

In normal human epidermis HLA-DR-antigen is only present on Langerhans' cells and the acrosyringeal epithelium. We investigated the distribution of HLA-DR-antigen in 78 specimens of various skin diseases by an immunoperoxidase method using a monoclonal anti-HLA-DR antibody. HLA-DR-antigen bearing keratinocytes were not only found in lichen planus and mycosis fungoides, as it has been referred previously, but were also observed in some cases of cutaneous B-cell lymphoma, pseudolymphoma, lupus erythematosus, parapsoriasis en plaque, bullous pemphigoid, drug reaction, contact dermatitis, actinic keratosis and verrucous carcinoma. Direct contact of lymphoid cells with keratinocytes was not necessary for Ia-antigen expression.