Expression of HLA-DR and T6 antigens on keratinocytes and dendritic cells. A comparative immunohistochemical study

The number, morphology, and distribution of cells with dendritic processes in the epidermis and dermis, as well as the expression of HLA-DR and T6 antigen on keratinocytes in 66 skin biopsy specimens have been studied. In the epidermis, OKT6+ cells with slender dendritic processes predominated in the upper layers and outnumbered OKIa1+ cells with dendritic processes, which were only fragmentarily stained and present throughout all layers. In the dermis, OKIa1+ cells with dendritic processes outnumbered OKT6+ cells with dendritic processes. Cases showing keratinocytic positivity for OKIa1 contained very few epidermal OKIa1+ cells with dendritic processes; cases showing surface staining of keratinocytes with OKT6 contained high numbers of epidermal OKT6+ cells with dendritic processes. We suggest that OKT6 and OKIa1 label distinctive subpopulations of epidermal and dermal dendritic cells and, as such provide complementary data.