Partial restoration of hair growth in the DEBR model for Alopecia areata after in vivo depletion of CD4+ T cells.

Alopecia areata (AA) is widely believed to be an autoimmune disease. Hair loss is associated with a peri- and intrafollicular inflammatory infiltrate of anagen hair follicles primarily composed of CD4 + and CD8 + cells. A previous investigation involved in vivo depletion of CD8 + cells in the DEBR rat model to examine the cells' potential pathogenic activity in AA. The rat model is used here in a comparable study of CD4 + cell pathogenic activity. Eight AA affected DEBR rats were given intraperitoneal injections of a CD4 + cell depleting OX-35/OX-38 monoclonal antibody (MoAb) cocktail over a 15-day therapy course. A further eight AA-affected rats comprised a control group and were injected with equivalent volumes of an irrelevant MoAb, OX-21. Changes in both CD4 + and CD8 + peripheral blood cell populations were analysed by flow cytometry, and macrophotography was used to record any changes in hair growth. Of the eight CD4 + cell-depleted rats six responded with hair growth. The rats revealed significant hair growth within 23 days of treatment initiation. With rapid replacement of the CD4 + cell population the newly generated pelage hair was eventually lost. Two control rats also showed limited hair growth within the 112-day study period. In vivo depletion of CD4 + cells partially restores hair growth in AA affected rats. The response suggests that CD4 + cells may be actively involved in the pathogenesis of AA. Further research may elucidate whether CD4 + cells have a direct effect on hair follicles or exert their influence through their classic T helper cell supporting role for CD8 + cells.