Ultrastructural studies of spontaneously regressing plane warts. Langerhans cells show marked activation.

Ultrastructural changes in Langerhans cells during spontaneous involution of plane warts were examined. In areas with activated macrophages and epidermal cell interaction, Langerhans cells showed signs of enhanced cellular activity with an increased number of Langerhans cell granules, as in contact dermatitis. The fine structure of Langerhans cell granules, however, was unusual in that the vesicular portion was surrounded by a membrane, and this portion frequently occurred independently taking the shape of a loop.