THE DEBR RAT, ALOPECIA-AREATA AND AUTOANTIBODIES TO THE HAIR FOLLICLE

Many attempts have been made to implicate hair follicle-specific autoa ntibodies in the pathogenesis of alopecia areata (AA), a suspected aut oimmune disease. Using the DEBR rat model for AA, we developed a refin ed indirect immunofluorescent technique to examine the sera from indiv idual rats for the presence of autoantibodies to the hair follicle and to other tissues. Sera were tested on cryostat sections from normal P VG/Ola rats and DEER rats. We found that DEER sera contained IgG autoa ntibodies specific for hair follicle epidermal differentia. While indi vidual sera revealed detailed differences, the target tissues identifi ed were hair cortex and cuticle and the inner root sheath, especially the Henle's layer. Some sera also contained autoantibodies specific fo r skeletal muscle and nuclear components. Of 10 young prelesional rats with apparently normal coats of hair, three had hair follicle autoant ibodies and seven had skeletal muscle autoantibodies. Nine of 10 activ e lesional rats with progressing hair loss had follicle autoantibodies and four had skeletal muscle autoantibodies. All 10 established lesio nal rats had follicle autoantibodies and one had muscle autoantibodies . Control sera from eight PVG/Ola rats showed no specific positive sta ining for hair follicle components or other tissues. Autoantibodies to intracellular hair follicle differentiation products were readily det ected in DEER rat sera. As these antibodies appeared to be generated a fter the appearance of the mononuclear follicular infiltrate, such aut oantibodies may be a secondary effect. We conclude that, while the pre sence of autoantibodies in the DEBR rat model is associated with autoi mmune activity, their role in the pathogenic progression of AA has yet to be ascertained.