Thymic regulation of autoimmune disease by accelerated differentiation of Foxp3+ regulatory T cells through IL-7 signaling pathway.

The exact role of adult thymus in autoimmune disease state is poorly understood. We show here that thymus regulated experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, as evidenced by loss of spontaneous recovery in thymectomized EAE mice. There was progressive enrichment for CD4 single-positive Foxp3(+) regulatory T cells in thymocytes during the course of EAE and they suppressed the disease when adoptively transferred. Thymus was shown to undergo an active process characterized by accelerated differentiation and proliferation of regulatory T (Treg) cells through a mechanism involving increased expression of IL-7 in stromal cells and dynamic expression of IL-7 receptor in thymic Treg cells. This process preceded EAE recovery and selectively affected Treg over non-Treg cells in the thymus, leading to increased output of thymic Treg cells and self-regulation of EAE. The study reveals a novel role of thymus in self-regulation of autoimmune condition.