The DEBR rat, alopecia areata and autoantibodies to the hair follicle.

Many attempts have been made to implicate hair follicle-specific autoantibodies in the pathogenesis of alopecia areata (AA), a suspected autoimmune disease. Using the DEBR rat model for AA, we developed a refined indirect immunofluorescent technique to examine the sera from individual rats for the presence of autoantibodies to the hair follicle and to other tissues. Sera were tested on cryostat sections from normal PVG/Ola rats and DEBR rats. We found that DEBR sera contained IgG autoantibodies specific for hair follicle epidermal differentia. While individual sera revealed detailed differences, the target tissues identified were hair cortex and cuticle and the inner root sheath, especially the Henle's layer. Some sera also contained autoantibodies specific for skeletal muscle and nuclear components. Of 10 young prelesional rats with apparently normal coats of hair, three had hair follicle autoantibodies and seven had skeletal muscle autoantibodies. Nine of 10 active lesional rats with progressing hair loss had follicle autoantibodies and four had skeletal muscle autoantibodies. All 10 established lesional rats had follicle autoantibodies and one had muscle autoantibodies. Control sera from eight PVG/Ola rats showed no specific positive staining for hair follicle components or other tissues. Autoantibodies to intracellular hair follicle differentiation products were readily detected in DEBR rat sera. As these antibodies appeared to be generated after the appearance of the mononuclear follicular infiltrate, such autoantibodies may be a secondary effect. We conclude that, while the presence of autoantibodies in the DEBR rat model is associated with autoimmune activity, their role in the pathogenic progression of AA has yet to be ascertained.