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.