Alopecia areata - animal models.

Several rodent models with spontaneous and induced alopecia areata (AA), a nonscarring inflammatory hair loss disease with suspected autoimmune elements, have been identified. Of these, the C3H/HeJ mouse and DEBR rat have been most extensively used in examining AA development. Flow cytometry and micro array characterization, manipulation of inflammatory cells by in vivo cell depletion or cell receptor blockade, lymph node cell transfer between affected and unaffected rodents, and the recent use of transgenic knockout mice have given important insights into the development of AA. From our current understanding of rodent models, the development of AA relies upon a general genetic susceptibility where major susceptibility genes may be supplemented by minor disease severity modifying genes. However, the actual onset of AA, its duration, extent, and persistence in individual rodents may be modified by epigenetic factors. Rodent AA seems to be fundamentally, but not exclusively, Th1 cell mediated. Onset of disease may be dependent on several factors including the break down of the putative anagen stage hair follicle immune privilege, appropriate antigen presentation with costimulation of lymphocytes, presence of autoreactive lymphocytes, and a deficiency of functional immune system regulatory cells. Rodents have already been used in examining a variety of current AA treatments and developing new therapies with some success. With a greater understanding of AA disease mechanisms through rodent model research, improved and more specific treatment interventions may be defined.