Phenotypic Analysis of T-Cells in Extensive Alopecia Areata Scalp Suggests Partial Tolerance

This study analyzed T-cell phenotypes and functional status in the scalp skin of 12 patients with extensive alopecia areata (EAA) and 6 control subjects using flow cytometry and immunohistochemical staining. EAA samples showed a lower percentage of CD-3-expressing cells, similar CD-4/CD-8 ratios to controls, and unique expression of CD-69, indicating T-cell activation. EAA T-cells produced less IL-2 and CD-8 T-cells produced less IFN-γ, with no increase in IFN-γ-producing cells compared to controls. These findings suggest that T-cell responses in EAA scalp are aberrantly regulated through peripheral T-cell tolerance mechanisms, potentially explaining the minimal inflammatory changes observed clinically.