Regulatory T cells in autoimmune kidney diseases and transplantation.

Regulatory T (T) 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 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 cells and genetic variations of T cell functional molecules can cause or predispose patients to the development of autoimmune diseases and other inflammatory disorders, including kidney diseases. T cells can potentially be utilized or targeted to treat immunological diseases and establish transplantation tolerance, for example, by expanding natural T cells in vivo using IL-2 or small molecules or by expanding them in vitro for adoptive T cell therapy. Efforts are also being made to convert antigen-specific conventional T cells into T cells and to generate chimeric antigen receptor T cells from natural T cells for adoptive T cell therapies with the aim of achieving antigen-specific immune suppression and tolerance in the clinic.