CD4 and autoimmune disease: In the last two decades, progress has been made to better characterize Treg cells in the context of autoimmune diseases and at least two main subsets of CD4+ Treg cells have been identified: natural nTreg cells that develop in the thymus following the recognition of self-antigens and express the transcription factor forkhead box P3 (FoxP3) [152] and inducible iTreg cells that generate from naïve CD4+ T cells under specific conditions of antigen-stimulation and in the presence of a particular cytokine milieu.