Reduction of Langerhans cells in human epidermis during PUVA therapy: a morphometric study.

Skin biopsies were obtained before and after PUVA therapy from the normal skin of 5 psoriatic patients. By electron microscopic morphometric techniques the pretreatment volume density of Langerhans cells within the epidermis was estimated to be approximately 1%. This density was reduced in all 5 patients after therapy. The volume density of Langerhans cell granules per Langerhans cell cytoplasm was on an average 0.8% and this density was reduced in 4 of the patients after therapy, while in one patient there was an increase. There was a reduced volume density of Langerhans cell granules per unit volume of epidermis in all 5 patients after therapy. The mean length of the Langerhans cell disc was 260 +/- 120, nm the mean thickness 40 nm and the mean diameter of the Langerhans cell vesicle 120 +/- 30 nm. None of these parameters changed after PUVA therapy. The reduced volume density of Langerhans cells is discussed in the context of possible implications for immune reactions in the skin.