Dendritic cell dynamics in progressive depigmentations

Abstract

Three types of dendritic cells (melanocytes, Langerhans cells, and α-dendritic cells) were identified and counted by the electron microscopic quantitation method of human epidermis. Five specimens of vitiligo of varying duration, four specimens of leucoderma acquisitum centrifugum, and two areas of spontaneous regression in Dubreuilh's precancerous melanosis (lentigo maligna) were compared with four normal controls. In vitiligo of relatively short duration, the number of melanocytes in the basal layer gradually decreased with the age of the lesion, and the number of α-dendritic cells (indeterminate cells, Zelickson) increased, their sum remaining fairly constant. It is postulated that active melanocytes become inactive and are converted into α-dendritic cells. Later, when the number of melanocytes approaches near zero, the α-dendritic cells also begin to decrease in number. It is only then that Langerhans cells show a change in distribution. Their total number remains constant, but Langerhans cells are now found to be increased in the basal layer. The events in leucoderma acquisitum centrifugum are similar. In regressing areas of Dubreuilh's precancerous melanosis, we found distinct signs of cytoplasmic degradation in the neoplastic melanocytes in addition to the other phenomena.