Why Do Organ Transplants Fail (Facts)

The first successful liver transplant was performed in 1954. The techniques have improved since: now over 29,000 organ transplants are performed in the U.S. each year. But it still provides a number of risks: matches are rare and rejection are still somewhat common. Certain procedures, like cornea transplants, have a 75 percent success rate over ten years, while heart, kidney and liver transplants have about a 70 percent organ survival rate over five years. So, what causes the body to reject a transplant? There are three main kinds of rejection, hyperacute, acute and chronic.

 Hyperacute happens almost instantaneously, within minutes or hours or the procedure. The recipient's body starts to reject the new organ or limb. Acute rejection can occur within a few months to a year from transplantation. Chronic rejection can happen over a few years.

 

Basically, your immune system is to blame: It is responsible for fighting off foreign invaders. A big part part of how it does its job is through the Major histocompatibility complex (MHC). The MHC's differentiates between your body's cells and cells that shouldn't be there. The MHC is made up of mostly glycoproteins on the walls of your cells. 

They act as tags that essentially say, "This is me". A white blood cell reads that tag, and helps it decide if that cell's coll or if it should destroy it. 

There's over 20 genes that code for the MHC and over 50 variations per gene, so there's a lot of different combinations, which is one of the reasons why it can be so hard to match a donor to a recipient. If the MHC recognizes the tags as foreign, your immune system produces T-cells which target it, essentially declaring war on it. There are a number of immunosuppressive drugs which can decrease the chances of this happening, but this requires some people having to be on them for life, sometimes taking up to 12 different medications daily.

 

Recent research holds some promise of reducing the need of such meds. In a study published in American Journal of Transplantation the researchers from UCSF used a two-tiered approach to tackle rejection. First they administered a drug called cyclophosphamide to mice which had transplanted tissues. 

The drug effectively killed off most of their T-cells. Then the mice received cell therapy which grew populations of certain TREG cells, which regulate T cells. And with more of these cells in place, they hold back the immune system from rejecting the organ or limb. According to the study nearly 80 percent of the mice accepted a transplant without the need for a lifelong regimen of drugs.