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One Way to Replace Islet Cells...
 
Researchers are looking a various sources of islets -- including engineered, proliferated, and regenerated islet cells -- and various methods of protecting these islets from the host's immune system -- including microencapsulation, macroencapsulation, and immune tolerance. To date, the use of microencapsulated porcine islets has shown the greatest initial efficacy while still presenting a number of remaining challenges. The following description illustrates this one particular approach to islet replacement without immunosuppression.

1. The Islet Donors Pigs are raised in a clean, specific-pathogen-free environment to provide a safe source of transplantable islets. 
 
Isolating the Islets 2. Islet Isolation Since the Islets of Langerhans are the only component of the pancreas which produces insulin, these islets must be separated from the rest of the pancreatic tissue. The isolation process yields hundreds of thousands of individual living islets.
 
 3. Islet Microencapsulation In order to protect the islets from the recipient's immune system, one or more living islets are enveloped in a microcapsule. In one implementation, the microcapsule is composed of three layers - alginate, polylysine, and alginate. This composition provides a biocompatible capsule which protects the islet, while itself being tolerated by the recipient's immune system.  
 
 
4. Islet Transplantation A large number of microencapsulated islets are injected into the recipient's peritoneal cavity in a simple procedure. In this site, the islets are able to receive blood-borne glucose, oxygen, and nutrients, and to release insulin. The recipient now enjoys normal insulin production in response to constantly changing blood sugar levels. 
 
5. Inside the Recipient Each microcapsule protects its islet as a result of openings in its structure. These openings are large enough to allow molecules such as glucose, oxygen, and insulin to pass between the blood and the islet, but are too small to allow the much larger components of the immune system, including antibodies and lymphocytes, to reach and attack the islet.  A look at the islet
 
 Boy eating icecream 6. The Outcome With these transplanted insulin factories operating inside the recipient, he or she is able to produce insulin internally in direct proportion to blood sugar levels. There is no more need for insulin injections or a restricted diet, and the dangerous consequences of high and low blood sugar can be avoided. 
 
The Puzzle is complete The Islet Foundation 
E-Mail: a.t.gordon@attglobal.net 

TIF Foundation Federal Tax Number BN 89439-1994-RR0001

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