Posted by Al Gordon on October 28, 2001 at 06:17:37:
In Reply to: xeno posted by Wondering on October 28, 2001 at 05:21:52:
I don't understand why Dr Harland is still talking about systemic immunosuppression for cell transplants. When you transplant a whole organ, you have to use systemic immunosuppression, because it is not feasible to isolate the new organ behind an immunobarrier. However, when you are transplanting individual cells (islets, neurons, liver cells), then it may be possible to use immunobarriers that protect only the transplanted cells, and leave the person's immune system healthy and whole.
None of the islet xenograft trials that I know about used systemic immunosuppression, because the researchers considered that its requirement would constitute failure. They all used microencapsulation, macroencapsulation, or protective sertoli cells.
I don't think it is clear that pig islets would require more immunosuppression than human islets (not that I would ever consider immunosuppression to be part of a general cure for diabetes). Pig islets do not contain alpha-Gal, the antigen that causes the hyperacute rejection of pig organs, and pig islets will not likely be subject to autoimmune attacks from the new host, which human islets will.
As for PERV, all I can say is "Show me one shred of evidence that PERV is a public health issue". We've been over this so many times, but it is part of the unquestioned mantra of researchers who are still working with human islets.
I know that Dr Harland made some very interesting advances using anti-CD40 Ligand as an immunotolerance agent, something that we all hoped would be less toxic than traditional immunosuppression. However, a patient's death during a clinical trial stopped, at least temporarily, trials of anti-CD40L. I don't think it was clear that the death was even caused by the anti-CD40L, and many thought it was the patient's pre-existing condition that caused fatal blood clots to form.
Al