Immunology of stem cells and cancer stem cells

The capacity of pluri-potent stem cells to repair the tissues in which stem cells reside holds great promise in development of novel cell replacement therapeutics for treating chronic and degenerative diseases. However, numerous reports show that stem cell therapy, even in an autologous setting, triggers lymphocyte infiltration and inflammation. Therefore, an important question to be answered is how the host immune system responds to engrafted autologous stem cells or allogeneous stem cells. In this brief review, we summarize the progress in several related areas in this field, including some of our data, in four sections: (1) immunogenicity of stem cells; (2) strategies to inhibit immune rejection to allograft stem cells; (3) immune responses to cancer stem cells; and (4) mesenchymal stem cells in immune regulation. Improvement of our understanding on these and other aspects of immune system-stem cell interplay would greatly facilitate the development of stem cell-based therapeutics for regenerative purposes.