Regulatory T cells in autoimmune kidney diseases and transplantation

Regulatory T (T_reg) cells that express the transcription factor forkhead box protein P3 (FOXP3) are naturally present in the immune system and have roles in the maintenance of immunological self-tolerance and immune system and tissue homeostasis. T_reg cells suppress T cell activation, expansion and effector functions by various mechanisms, particularly by controlling the functions of antigen-presenting cells. They can also contribute to tissue repair by suppressing inflammation and facilitating tissue regeneration, for example, via the production of growth factors and the promotion of stem cell differentiation and proliferation. Monogenic anomalies of T_reg cells and genetic variations of T_reg cell functional molecules can cause or predispose patients to the development of autoimmune diseases and other inflammatory disorders, including kidney diseases. T_reg cells can potentially be utilized or targeted to treat immunological diseases and establish transplantation tolerance, for example, by expanding natural T_reg cells in vivo using IL-2 or small molecules or by expanding them in vitro for adoptive T_reg cell therapy. Efforts are also being made to convert antigen-specific conventional T cells into T_reg cells and to generate chimeric antigen receptor T_reg cells from natural T_reg cells for adoptive T_reg cell therapies with the aim of achieving antigen-specific immune suppression and tolerance in the clinic.