Currently, when an organ transplant is performed, the patient has to take immunosuppressive drugs to prevent his or her system from rejecting the new organ. These drugs must be taken for life and have numerous side effects. In a phase 1 clinical trial, researchers gave patients receiving a liver transplant regulatory dendritic cells derived from the original donor, with the hypothesis that these cells could 'teach' the recipient's immune system to tolerate the new organ. The research, published in Science Translational Medicine, suggests that this treatment could reduce or even eliminate the need for long-term use of immunosuppressants.