Immunologic Cytotoxicity in Alopecia Areata: Apoptosis of Dermal Papilla Cells in Alopecia Areata

Abstract

medium, i.e., that in which confluent dermal papilla cells had been grown for 48 h, was tested for growth-promoting activity on a human skin keratinocyte cell line using an MTT assay. Normal dermal papilla cell medium stimulated keratinocyte growth signif­ icandy at low concentrations compared to control non-conditioned medium but alopecia areata cell medium had no effect. This suggests that dermal papilla cells from normal follicles secrete soluble mitogenic factors that are not produced by alopecia areata cells. This obviously merits further investigation as the absence of such mitogenic factors could be involved in the altered keratinocyte activity in the alopecia areata hair follicle. Overall, there are a number of aspects that implicate the dermal papilla in the pathogenesis of alopecia areata. Although it seems likely that the dermal papilla plays a key role at an early stage in the disease, it is not yet clear whether this is an etiologic role or part of the follicle's defense responses to an insult elsewhere in the follicle such as the melanocytes or follicular keratinocytes. THE JOURNAL OF INVESTIGATIVE DERMATOLOGY