T regulatory cells (Treg) are distinguished by CD4+, CD25+, GITR+, CTLA-4+. Some of T regs also express the transcription factor Foxp3 (nTreg).
Treg subsets include:
- Natural Tregs (nTreg). nTregs develop in the thymus and constitutively express Foxp3 and CD25. They depend upon IL-2 for their survival.
- Induced Tregs (iTreg). iTregs are induced from naïve CD4 in the periphery. They express Foxp3 only after development by TGF-b.
- T Regulatory 1 (Tr1). Tr1 do not express CD25 or Foxp3. They depend on IL-10 from DCs for development. Tr1 produce high levels of IL-10.
Regulatory T cells - 6 groups have been described (click to enlarge the image).
A lack of regulatory T (TReg) cells that express CD4, CD25 and forkhead box P3 (FOXP3) results in severe autoimmunity in humans (IPEX).
There has been intense investigation aimed at determining how they protect an organism from autoimmunity and whether defects in their number or function contribute to the development of autoimmunity.
The next phase of investigation — focused on defining the role that defects in TReg cells have in human autoimmunity — is now underway. This knowledge might have a significant impact on the diagnosis and treatment of autoimmune diseases.
Mechanisms of impaired regulation by CD4+CD25+FOXP3+ regulatory T cells in human autoimmune diseases. Nature Reviews Immunology 10, 849-859 (December 2010) | doi:10.1038/nri2889
Regulatory T cells
Image source: A scanning electron microscope (SEM) image of a single human lymphocyte.Wikipedia, public domain.