Irradiating intestines before they are transplanted can slash the risk of rejection in the recipient patient, say US researchers.
About 85 per cent of patients who receive small intestine transplants experience some rejection of the organ within the first month. Doctors can inject more powerful anti-rejection drugs, but this further dampens the patient鈥檚 immune system and increases their risk of infection. In extreme cases, rejection can lead to death.
鈥淲e find that rejection up to four weeks after transplant is the major risk factor for patients having grafts,鈥� says Kareem Abu-Elmagd of the University of Pittsburgh, US, who led the new research.
Advertisement
Abu-Elmagd鈥檚 team exposed small intestines to very low doses of radiation for a few minutes before they were transplanted. Only one of 13 recipient patients experienced any rejection.
The small intestine contains very large numbers of lymphocytes 鈥� immune system cells that can trigger the recipient patient鈥檚 immune system to attack the organ. These lymphocytes are very susceptible to low level radiation, says Abu-Elmagd.
鈥淲e are really very excited by these results,鈥� says Abu-Elmagd. 鈥淭his strategy could significantly improve the outcomes for intestinal transplantation.鈥�
Living together
The patients also received injections of bone marrow from the donor patient. Bone marrow contains immature immune cells. Infusing these cells into the recipient鈥檚 blood seems to encourage donor and recipient cells to exist together. This also helps prevent rejection.
Of the 13 patients, nine received small bowel alone, one received a liver and intestine transplant, and three received multiple organ transplants. One patient, who had received small intestine only, rejected the organ and died from complications of the anti-rejection treatment. The other patients have not experienced rejection more than one year after transplant.
The radiation treatment killed large numbers of lymphocytes but did not harm normal intestinal cells, says Abu-Elmagd. This is because cells that are actively multiplying 鈥� such as the lympocytes 鈥� are more susceptible to the radiation.
Lung tissue also contains large numbers of lymphocytes. Abu-Elmagd鈥檚 team is now conducting animal studies using irradiated lungs. If these go well, human clinical trials will follow, he says.
Abu-Elmagd presented his findings to the Transplant 2001 conference in Chicago.