In vivo depletion of CD8(+) T cells restores hair growth in the DEBR model for alopecia areata

Alopecia areata (AA) is a putative autoimmune disease in which anagen hair follicles are the target of immune cell attack. While both CD4(+) and CD8(+) T lymphocytes are prominent in the infiltrate, their respective roles in the pathogenesis of AA remain unknown, Here we directly investigated the activity of CD8(+) cells in the inhibition of hair growth using the Dundee experimental bald rat (DEER) model for AA. Eight lesional DEBRs were fully depleted of their CD8(+) cells by intraperitoneal injection of OX-8 monoclonal antibody (MoAb) specific for these cells over a 15-day therapy course, A control group of eight lesional rats was injected with the irrelevant MoAb OX-21. Sequential blood samples were analysed by now cytometry to observe changes in the CD8(+) cell population and macrophotography used to record changes in hair growth activity. All eight CD8(+) depleted rats started to regrow hair within 29 days from the start of treatment, the final response ranging from sparse regrowth to a near normal coat, While two rats maintained their new pelage, the remainder lost hair as the CD8(+) population in peripheral blood increased, Two of the control rats also showed hair regrowth over the experimental period of 156 days, These results suggest that CD8(+) cells play an active part in the pathogenesis of AA, As hair production did not fully recover in all animals, immune mechanisms other than CD8(+) cells may be involved in effecting hair loss, However, analysis of CD8(+) cell levels in the skin of CD8(+) depleted rats may help resolve their full importance in AA.