Regulatory T cells (Treg) and CD4+ T cells recognise AChR epitopes and trigger B cells to produce antibodies.1, , –4 Foxp3+ CD4+ Treg cells influence the amount of autoreactive T cells, regulate the activity of autoreactive B cells, and therefore regulate the production of AChR antibodies.5 In patients with MG, the frequency of Foxp3+ CD4+ Treg cells is significantly lowered, contributing to the pathogenesis of MG.6, –8 However, the predisposing factors for MG are still unknown. Here, FOXP3 is linked to myasthenia gravis.