From Ohio, USA:
What progress is being made on using encapsulated islets?
I had a chance to talk this morning to one member of the research team here who spends all his time on the transplant issue and who is deeply into the encapsulation business himself.
First a very simplistic paragraph on the basic immunology. The white blood cells that are responsible for active immunity i.e. not antibody formation, start off in the bone marrow and then migrate through the thymus where they learn to differentiate 'self' from 'non-self'; they do this by recognising something in the configuration of the cell wall protein. In Type 1 diabetes the surface of the islet cell has certain characteristics that are determined genetically that in turn make that cell surface more vulnerable to be further altered by a virus or some other agent. Once that happens then the macrophage cells perceive the islet as 'non-self' and after triggering other lymphocytes to do the same, the cell is eventually destroyed.
A remedy for this could be immunosuppression at an early stage; but this has not been successful.
Another approach would be to replace the islet cells. For this to work, however, you have to protect the transplanted cells from the host's immune system, either with drugs like Imuran or by encapsulation in some alginate. This separation also opens the possibility of using xenotransplants (cells from another species) which is important in diabetes as there aren't enough human cells to go around. There are troubles though. You cant get the capsules out again, for a start (something the FDA requires) and the capsules may disintegrate. Even if they don't, insulin itself is antigenic and the antibodies may get back into the capsule and affect the islet cell function.
In short, although islet cell autografts work splendidly in pancreatitis cases, and pancreas transplants are of help in end-stage disease with renal complications, the use of encapsulated islets in man is still a hope rather than a reality. In the meantime, more sophisticated pumps, new substituted and long term insulins, and perhaps before too long non-invasive methods of home blood glucose monitoring, offer competing routes to immaculate control.
Original posting 6 Oct 96
Last Updated: Tuesday April 06, 2010 15:08:52
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