Quantitation of dendritic cells in normal and abnormal human epidermis using monoclonal antibodies directed against Ia and HTA antigens

Two monoclonal antibodies, NAI 34 and DA6 231, have been used as surface markers to count epidermal Langerhans cells in normal skin, allergic contact dermatitis, and mycosis fungoides of the plaque and poikilodermatous varieties. The antibodies recognized the HTA (human thymocyte antigen) and Ia antigens, respectively. In all situations the numbers of cells labeled by the two antibodies differed. In normal skin 75% of dendritic cells were labeled by both antibodies and 25% were labeled by NAI 34 alone. In contact dermatitis there is an increase in dendritic cells labeled by both antibodies and this pattern is also seen in untreated plaque stage mycosis fungoides. In poikilodermatous mycosis fungoides, striking staining of the epidermal keratinocytes with DA6 231 is seen with no dendritic cells labeled. Dendritic cells are, however, clearly seen with NAI 34 staining. Numbers of dendritic cells labeled by both antibodies fall during PUVA therapy.