CTLA4 and diabetes mellitus: Naturally occurring CD4 + regulatory T cells (Tregs), which specifically express the transcription factor FoxP3 in the nucleus and CD25 and CTLA−4 on the cell surface, are a functionally distinct T cell subpopulation actively engaged in the maintenance of immunological self-tolerance and homeostasis.[27] Emerging data suggest, in diabetes patients, function of specific T-lymphocyte populations, including Tregs has altered.[4] In the peripheral blood of diabetic patients, the level of CD4 + Tregs is significantly disordered.