"The absence of a need for immune suppression after transplanting from one species to another was such an unexpected and encouraging discovery that we wanted to find out more about why that worked and under what conditions it is possible," Hammerman says.
Superficially, there appears to be relatively little difference between pancreatic primordia from 28-day-old and 35-day-old pig embryos. "To put this in perspective, pig gestation is about 120 days, and it takes every bit of that time for the pancreas to fully develop," Hammerman explains. "There is no pancreas before embryonic day 28, and 35-day-old pancreas is still very early-stage tissue."
Hammerman and Rogers have demonstrated that the pancreatic transplants aren't altering the rats' immune systems. They showed that rats with successful pancreatic transplants still reject a transplant of a different type of pig primordia, embryonic kidney tissue, if they are not given immune suppression drugs.
Prior research by other scientists into the immune system's interactions with transplants had suggested that a second unsuccessful organ transplant can "wake up" the immune system and lead it to reject an earlier successful transplant of a different organ. However, this didn't happen in the rats that rejected secondary kidney transplants.
To Hammerman, this suggests that the pancreatic primordia may be effectively invisible to the rat's immune system. He theorizes that this invisibility is a result of the unusual ways 28-day-old tissues differentiate after transplantation. He and Rogers have shown that no part of the digestive components of the pancreas, which are not needed to treat diabetes, develops after cross-species transplantation of such primordia.
Even the endocrine
Source:Washington University School of Medicine