An ultraviolet B radiation protocol for complete depletion of human epidermal Langerhans cells

We report an ultraviolet B (UVB) protocol that achieves essentially complete depletion of Langerhans cells (LC) from human skin, while leaving the skin clinically intact. Sixteen human volunteers of skin types II and III were exposed to 144 mJ/cm2 of UVB each day for 4 successive days, on a 2-cm-diameter circle of buttock skin. In each case the irradiated skin showed redness and mild edema but no vesiculation or ulceration. One hour after the last exposure a 4-mm punch biopsy was taken from the center of the irradiated site. The epidermal sheet from each sample was separated and exposed to CD-1 antibody (12 samples) or HLA-DR antibody (4 samples) and the density of LC was assessed by immunofluorescence light microscopy. In each case the epidermal LC population was severely depleted to less than 20 cells/mm2, from a baseline of approximately 565 cells/mm2, and in many cases no morphologically normal LC remained. This simple protocol thus provides intact human skin completely depleted of LC. Such skin will provide an appropriate model for the in vivo study of the immune function in human skin deprived of its epidermal antigen-presenting capacity.