HLA-DR ANTIGEN EXPRESSION ON THE KERATINOCYTE SURFACE IN DERMATOSES CHARACTERIZED BY LYMPHOCYTIC EXOCYTOSIS (EG PITYRIASIS ROSEA)

The immunoperoxidase staining pattern of the epidermis was investigated in several dermatoses characterized by exocytosis of mononuclear cells into the epidermis. HLA-DR antigens showed an intercellular distribution in localized areas of the epidermis in 9 of 10 cases of pityriasis rosea, all 4 cases of spontaneously regressing flat warts, 2 cases of pityriasis lichenoides chronica, 2 of Schamberg''s disease and 1 case of lichen striatus. Lichen planus and mycosis fungoides cases were used as positive controls. OKT6 antigen was recognized only on the dendritic cells of the epidermis in all these cases. Judging from the distributon of Langerhans cells, the epidermal intercellular HLA-DR antigen seems to be expressed on the keratinocytes in such diseases, and this feature was confirmed by immunoelectron microscopy. The expression of HLA-DR antigen on keratinocytes in these dermatoses is linked to cellular immune reactions involving the epidermis.