Transferred NOD and B6 CD4+ Tregs undergo comparable homeostatic proliferation in lymphopenic mice. Five hundred thousand purified CD4+CD25+ cells from NOD or B6 mice were labeled with CFSE and transferred into NOD.SCID or B6.SCID mice, respectively. (a) Four or (b) six days after transfer, LN and spleen cells were collected and labeled with CD4 and CD25 antibodies. CD4+ cells were gated and analyzed for CFSE dilution among donor cells. Percentages (a and b, upper and center panels) and absolute numbers (a and b, lower panels) of CFSE low (i.e., cells that have undergone proliferation) donor cells are shown. Each symbol represents data from an individual animal.