Medical News Today -- Researchers have shown that immune-defense cells influenced by embryonic stem cell-derived cells can help prevent the rejection of hearts transplanted into mice, all without the use of immunosuppressive drugs. The University of Iowa and the Iowa City Veterans Affairs (VA) Medical Center finding has implications for possible improvements in organ and bone marrow transplantation for humans. The study results appeared Friday in the online journal PLoS ONE, published by the Public Library of Science, at http://dx.plos.org/10.1371/journal.pone.0003212.