Question: can stem cells be rejected by immune system?

Matthew Tomlinson answered on 12 Nov 2013:

Hi haben

That’s a really good question and has a few answers. Immune rejection depends on whether the immune cells can recognise the foreign cells as different and this is decided by a few proteins on the cell surface. This kind of works like a bar code, if the immune cells recognise the protein they leave the cell alone, if they don’t recognise it they try to kill it.

So stem cells with the same bar code as the immune cells are fine, this is why for bone marrow transplants need matching donors, these are people, often related, that have the same bar code as the patient. The immune system will tolerate these stem cells because they are similar enough to the patients. However, if the stem cells are different the immune system will reject them. There are some bone marrow cells which seem to be allowed by the immune system without matching the patients immune system, but these are very rare and there is a lot into research into why this happens and how these cells can be used.

Another type of stem cell which is allowed by the immune system is an induced pluripotent stem cell. These are normal body cells taken from a patient that are turned into stem cells by adding 4 chemicals. Because these cells are from the same patient the immune system does not recognise them as different and so allows them to stay in the body. Most of the work with these cells is in mice but the results look promising for human trials.

Embryonic stem cells can trigger an immune response because they most often come from a donor embryo which has a different surface bar code and so is not recognised by the immune system. However there was research from the US in 2011 which showed that treating a patient with some drugs to reduce the immune system allowed embryonic stem cells to survive in a recipient.

So in short, yes they can, but not all the time and there are ways around it, I hope that helps!