CD4 and alopecia: In the C3H mouse model, the temporary depletion of CD4+ T cells triggers partial hair regrowth (29), whereas the adoptive transfer of CD4+CD25- T cells from AA mouse skin draining lymph nodes (SDLNs) to healthy mice induces systemic alopecia (29, 51), highlighting the critical role of CD4+ T cell helper functions in AA pathogenesis (29).