Immunohistochemical analysis of FOXP3+ regulatory T cells in healthy human skin and autoimmune dermatoses.

Background: Regulatory T cells (Tregs) play an important role in autoimmune diseases. In skin, the presence of Tregs is thought to be mandatory for suppression of autoreactive T cells. Here, we assess the number of Tregs in skin of healthy subjects and patients with an autoimmune dermatosis.

Methods: Immunohistochemical stainings for CD3 and FOXP3 on skin biopsies of healthy subjects and subjects with psoriasis, vitiligo, pemphigus vulgaris, bullous pemphigoid, and halo nevus to assess the number of T and regulatory T cells, respectively.

Results: Low numbers of CD3+ and FOXP3+ cells were seen in the skin of healthy controls (median = 0.5%). A significantly higher frequency of Tregs was seen in lesional skin of patients with psoriasis (median = 12.4%) and patients with bullous pemphigoid (median = 10.1%) as compared to controls. In vitiligo (median = 0.0%), pemphigus vulgaris (median = 5.2%), and halo nevi (median = 5.4%), no significant difference in number of FOXP3+ cells was observed when compared to controls.

Conclusions: As confirmed in the literature, few Tregs were seen in healthy skin. A high number of Tregs were present in lesional skin from patients with psoriasis and bullous pemphigoid. These results support the hypothesis that not a decrease in number but rather a decrease in function of Tregs would be at the basis of autoimmune skin diseases, which could result in unrestrained activation autoreactive T cells in skin of patients with autoimmune dermatoses.