CD4 and Autoimmunity: These cells, originally described to suppress autoimmunity, are named regulatory T cells (Tregs) and represent a subset of CD4+ T helper (Th) cells expressing the forkhead box P3 (Foxp3) transcription factor as well as high levels of the interleukin (IL)-2 high-affinity receptor IL-2Rα or CD25 (Sakaguchi et al. 2008).