Low-Dose IL-2 for Treating Moderate to Severe Alopecia Areata: A 52-Week Multicenter Prospective Placebo-Controlled Study Assessing Its Impact on T Regulatory Cell and NK Cell Populations

This 52-week multicenter prospective placebo-controlled study assessed the impact of low-dose IL-2 on T regulatory (Treg) and NK cell populations in 43 patients with severe alopecia areata (AA). Despite a significant increase in peripheral Tregs, the treatment did not significantly stimulate hair regrowth, with only 14.3% of the IL-2 group achieving a 50% reduction in the Severity of Alopecia Tool score compared to 9.1% in the placebo group (P = 0.66). The study found no significant improvement in body hair, nails, or patient satisfaction. Adverse events, primarily flu-like symptoms and eosinophilia, were more frequent in the IL-2 group. The lack of clinical efficacy was attributed to the increase being limited to naive Tregs without expansion of effector and memory populations with skin homing capabilities.