Fig. 3

Nature of regulatory T cells (Tregs). Representing a specialized subset of T lymphocytes, Tregs commonly exhibit a distinctive genetic phenotype with upregulation of genes encoding signature proteins, such as FOXP3. Essentially, Tregs originate from two sources: (1) the majority of Tregs arise during thymic T cell maturation (nTregs). They constitute a steady population carrying CD4 and expressing T cell receptors (TCRs) that enable them to recognize self-antigens. (2) Tregs can also be generated in the periphery from conventional CD4⁺ T cells upon antigenic exposure and stimulated by high levels of TGF-β, retinoic acid, and IL-10. Such iTregs are equipped with TCRs that can also detect foreign antigens. Different Treg subsets including nTregs, iTregs and Foxp3⁻ Tregs circulate in the bloodstream. APC antigen presenting cell, CD4 cluster of differentiation 4, Foxp3 forkhead box protein P3, IL-2 interleukin-2, iTregs induced Tregs, MHC II major histocompatibility complex II, nTregs natural Tregs, TGF-β tumor growth factor-beta