Human embryonic stem cells trigger an immune response in mice, and if the same thing happens in humans, stem cell treatments could be much further away then previously thought. To counter this, scientists found that common anti-rejection medications could counter the mice’s immune response. However, the new finding hurts prior hopes that the immune system gave foreign embryonic stem cells no problems.
Embryonic stem cells form all the cells found in an embryo. Some researchers have suggested that the immune system ignores them to allow the growth of a fetus that contains both maternal and paternal genetic material. Such an immunological exemption would counter concerns about using cells therapeutically that don’t exactly match the recipient’s immune system. The body would, according to theory, not reject the new tissue or organ.
After injecting human embryonic stem cells into mice, those cells died within 10 days in mice with good immune systems but survived and multiplied in the mice with impaired immune responses. Further injections into the normally functioning mice led to exponentially more rapid cell death. This was a sign that the mice’s immune system was recognizing and rejecting the cells, just like it would do with any pathogens.
Medicating the mice with normal immune systems with a combination of two common anti-rejection compounds — tacrolimus and sirolimus — allowed those cells to survive for up to 28 days, the team said. But this certainly complicates matters.