Posted by Lauren Rugani on April 27, 2009
Right now, more than 100,000 people in the United States are waiting for an organ transplant. Unfortunately, scientists can’t assure that everyone on the list will receive a new organ, but new research suggests that someday they will be able to ensure that whatever transplants can be made will be more successful over the long term.
Despite careful consideration of certain factors like tissue match and blood type between organ donors and recipients, many transplants still fail because a patient’s immune system rejects the new organ the same way it would reject any other foreign object, such as a virus or bacterial infection: by trying to kill it. Recently, Australian scientists developed a way to temporarily disable this reaction by the immune system for just enough time to transplant an organ and encourage the body to accept the new tissue as its own.
They tested the experimental method in healthy mice by injecting an immune system molecule called interleukin-2 (IL-2) and an antibody for three consecutive days. IL-2 is a hormone that plays a significant role in the body’s defense against microbial infection and helps distinguish the body’s own cells from foreign ones. Its actions can be controlled by combining the molecule with any number of antibodies; in this particular case, the researchers were able to increase the number of regulatory T cells in the body, which subdue the body’s “killer” T cells that would normally attack the transplanted organ.
The team then injected insulin-producing cells into the mice. After two weeks, 80% of the mice accepted the new cells as their own; the number of regulatory T cells dropped back to normal and the immune system regained function of its killer T cells that would stave off infection but leave the transplanted cells alone. Some mice even tolerated the transplant for up to 300 days. The team is cautiously excited about these results, as they should be. The numbers are comparable to the survival rate of human pancreatic transplant patients after one year.
The biggest advantage of this method is that transplant patients can receive new organs without ever having to take immunosuppresant drugs, which often have toxic side effects. The researchers are now working to fully understand the mechanisms behind the molecular combination so that they can expand their research to more difficult organ grafts including kidneys and hearts. Eventually they hope to understand the process well enough to duplicate the results in human trials.