Mediation of alopecia areata by cooperation between CD4+ and CD8+ T lymphocytes: transfer to human scalp explants on Prkdc(scid) mice.

OBJECTIVE To determine the role of CD4+ and CD8+ T lymphocytes in the pathogenesis of alopecia areata. DESIGN Relapse of alopecia areata was induced in autologous human scalp grafts on Prkdc(scid) mice by injection of activated T lymphocytes derived from lesional skin. CD4+ and CD8+ T cells were separated by magnetic beads before injection. SETTING University-based dermatology practice. PARTICIPANTS Eleven patients with either alopecia totalis or severe alopecia areata. MAIN OUTCOME MEASURES Hair regrowth, hair loss, and immunohistochemical findings of scalp explants. INTERVENTION Transfer of scalp T cells to autologous lesional scalp explants on Prkdc(scid) mice. RESULTS Injection of unseparated T cells and mixed CD4+ plus CD8+ T cells resulted in significant hair loss (P<.01) in 5 of 5 experiments. However, injection of purified CD4+ or CD8+ T cells alone did not result in reproducible hair loss. CD4+ and CD8+ T cells induced follicular expression of intercellular adhesion molecule 1 (CD54), HLA-DR, and HLA-A, HLA-B, and HLA-C after injection into scalp grafts. CONCLUSIONS CD4+ and CD8+ T cells have a role in the pathogenesis of alopecia areata. It is hypothesized that CD8+ T cells act as the effector cells, with CD4+ T cell help. It is now necessary to look for HLA-A, HLA-B, and HLA-C associations with alopecia areata. Therapeutic manipulations that interfere with CD8+ activity should be examined.