In the September 11th online edition of Stem Cells, Israeli scientists L. Zangi et al. from the Weizmann Insititute of Science (Rehovolt, Israel) reported the results of their study on the immunoregulatory activity of mesenchymal stem/stromal cells (MSCs) and the controversial concept that they are immune privileged stem cells. The investigators conducted in vivo imaging experiments evaluating the survival of luciferase-labeled MSC (Luc+MSCs) implanted into allogeneic recipients. The experimental data showed MSCs survived longer than fibroblasts (Fb) in allogeneic recipients, but shorter survival rates when they were implanted into syngeneic or immune deficient mice. The study also revealed that MSCs induced a memory response as a result of Luc+Fb being rejected by mice which previously rejected Luc+MSCs grafts. Additionally, transgenic mice bearing a T cell receptor (TCR) transgene against a specific MHCI or MHCII showed an increase in CD4+ or CD8+ expressing a memory T cell phenotype (CD122+, CD44+, and CD62L^low) in mice primed and challenged with MSCs expressing the cognate MHC haplotype. The authors concluded from their experimental results that "MSC are not intrinsically immune privileged and under allogeneic settings these cells induce rejection, followed by an immune memory" response.