Effects of Low-Dose Recombinant Interleukin 2 to Promote T-Regulatory Cells in Alopecia Areata

IMPORTANCE An impaired inhibitory function of circulating CD4(+)CD25(+) regulatory T (Treg) cells was reported to play a key role in alopecia areata (AA). We report the first use to our knowledge of low-dose interleukin 2 for treating severe AA by promoting the recruitment of Treg cells. OBSERVATIONS We conducted a prospective open pilot study in 5 patients with severe AA resistant to previous systemic treatments. Subcutaneous interleukin 2 (1.5 million IU/d) was administered during 5 days, followed by three 5-day courses of 3 million IU/d at weeks 3, 6, and 9. The primary outcome was the evolution of the Severity of Alopecia Tool (SALT) score, evaluated by 2 independent investigators on standardized photographs. Lesional skin biopsy specimens and peripheral blood lymphocyte phenotype were analyzed. The median SALT score went from 82 (range, 63-100) at baseline to 69 (range, 28-100) at 6 months. Immunochemical analysis revealed the appearance or a notable increase in Treg cell count in 4 of 5 patients at the end of the treatment compared with baseline. No serious adverse event was reported. CONCLUSIONS AND RELEVANCE The partial regrowth achieved in 4 of 5 patients and the recruitment of Treg cells in lesional skin support the interest of promoting Treg cells for treating AA. Further investigations are now required to confirm and to optimize the design in order to enhance the Treg cell response.