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How Hepatitis Escapes the Immune System

Credit: Frederic Sierro

The liver’s unusual cellular architecture makes blood flow slower than in other organs. Perforations of the lining of the blood vessels within the liver allow a unique contact between the circulating blood cells (red) and the liver cells (green), and explains why activated T cells (blue) are efficiently retained in the liver. Credit: Frederic Sierro

By Patrick Bertolino and David Bowen

Recent discoveries about the unusual behaviour of immune cells in the liver could open the way to new strategies for transplantation and the treatment of viral hepatitis.

Patrick Bertolino and David Bowen are co-heads of the Liver Immunology group at the Centenary Institute in Sydney.

The full text of this article can be purchased from Informit.

The relationship between the liver and the immune system is unique. During pregnancy, the foetal liver produces the baby’s first blood cells. After birth, the liver hands over this role to the bone marrow but continues to maintain an unusual relationship with the immune system.

In fact, the liver is the only place outside of the lymph nodes where white blood cells, or T cells that have not seen foreign material before, can be retained and activated. Strangely, though, T cells activated in the liver do not go out and kill foreign invaders of the body – they are actually tolerant of them. To ensure this, the liver destroys most of the T cells it has activated.

We have recently found how it goes about doing this. Not only does the process explain several puzzling observations of the behaviour of the liver, it could also lead to new treatments for a variety of conditions, including viral hepatitis.

The liver is the largest internal organ of the body and has always been considered exceptional. The ancient Greeks seemed to have a feel for its properties: in Greek mythology Prometheus, a Titan who irritated Zeus by stealing fire and giving it to humans, was punished by being chained to a rock where his liver was eaten away each day by an eagle, only for it to regenerate to its original size every night.

This ancient story beautifully illustrates a...

The full text of this article can be purchased from Informit.