Regulatory T-cells in alopecia areata

Background: Alopecia areata (AA) is believed to have an autoimmune mechanism in which the hair follicles are targeted by CD4+ and CD8+ lymphocytes. Studies investigating the autoimmune mechanism of other cutaneous diseases, including vitiligo, showed that T_reg is a component of cutaneous immune privilege. Our study uses immunohistochemical staining in formalin-fixed, paraffin-embedded tissue to examine the percentage of CD4⁺ FoxP3⁺ , CD25⁺ FoxP3⁺ , and CD8⁺ FoxP3⁺ T_reg in AA in human specimens.

Methods: Immunohistochemical double staining for CD4⁺ FoxP3⁺ , CD25⁺ FoxP3⁺ , and CD8⁺ FoxP3⁺ was performed on 12 AA cases and 12 other autoimmune and non-autoimmune cutaneous diseases. The frequency of CD4⁺ FoxP3⁺ , CD25⁺ FoxP3⁺ , and CD8⁺ FoxP3⁺ T_reg was counted and expressed as a percentage of total CD4⁺ , CD25⁺ , and CD8⁺ lymphocytes, respectively, in order to account for intersample inflammatory response variability.

Results: There was a significant reduction in the mean frequency of CD4⁺ FoxP3⁺ and CD25⁺ FoxP3⁺ in AA when compared to other autoimmune and non-autoimmune cutaneous diseases.

Conclusion: T_reg is significantly lower in AA when compared to other cutaneous diseases. Additionally, this immunohistochemical-staining protocol may be useful to evaluate T_reg in formalin-fixed, paraffin-embedded specimens for other cutaneous diseases. Studies examining T_reg in AA and other cutaneous diseases may have implications for future interventions.