A Maynooth researcher is looking at why the body does not reject transplanted adult stem cells, opening up the possibility of new treatments, writes Dick Ahlstrom
Transplanted tissues face the threat of rejection by the receiving host with few exceptions, one glaring example being the foetus. A researcher at NUI Maynooth is studying how the foetus accomplishes this to better understand how another tissue type, adult stem cells, also manage to evade immune system attack.
"Adult stem cells seem to avoid the normal rejection process," explains Dr Bernard Mahon, a senior lecturer in Maynooth and a scientist working in its Institute of Immunology.
The powerful immune response clears out anything it sees as foreign, such as bacteria and viruses, and ignores tissues it considers "self". Yet clearly the developing foetus manages to look like "self" despite being completely foreign tissue.
The biochemistry behind this is helping to inform scientists who are looking at how adult stem cells also apparently become invisible to the immune system.
Dr Mahon is involved in collaborative research with scientists in NUI Galway's Regenerative Medicine Institute (Remedi). He is seeking to confirm conclusively that adult stem cells introduced to a non-matched host do survive without triggering an immune system attack.
"Certainly the animal data shows that this is the case. We are trying to confirm that adult stem cells disobey the rules of rejection. It seems these stem cells avoid the normal rejection process and that is a very surprising attribute."
Funding for the work has come via Science Foundation Ireland, with Remedi serving as the research leader. "We are looking at how the immune system of the host allows the stem cells to survive. There are a variety of ways that the stem cells modulate the immune system," he says.
Similar work on how the foetus does this pointed towards a number of proteins and biochemical signals that protected the non-self foetal tissue.
"It seems the stem cells show some of those features. They have the ability to differentiate, divide in a controlled way and the ability to modulate the immune system."
Dr Mahon has found that the foetus and adult stem cells share four or five signals, but not the full range of biochemical markers used by the foetus. "The stem cell seems to teach a particular type of immune cell to accept it, the regulatory T-cell."
Also known as suppressor T-cells, this subgroup of T-cells serves to dampen down immune system activity and prevent immune attacks on the host's own tissues. This gives them a crucial role in controlling our immune response, knowledge offering something that could prove valuable in transplantation therapies and new medical treatments.
"The real goal is if we are going to use adult stem cells as a therapy to correct conditions with a genetic defect, it is going to be much easier to scale these treatments up if we can use mismatched stem cells," Dr Mahon says.
It can be very difficult to find and harvest adult stem cells, but if the host genuinely tolerates their introduction, even if mismatched, then stem cell lines could potentially be cultured and bulked up for use in any patient. "It would make it a viable therapy and much cheaper," he says.