How the liver talks to white blood cells

Sydney researchers have shown for the first time how liver cells make contact with T cells in the body.

Dr Patrick Bertolino, head of the Centenary Institute's liver immunology group, and colleagues Dr Alessandra Warren and Professor David Le Couteur of Concord RG Hospital have described the way liver cells and white blood cells (T cells) reach out to each other through tiny openings between cells lining the walls of blood vessels in the liver.

Using electron microscopy, the team was able to magnify cells within a mouse liver by up to 20,000 times their original size and photograph their activity in three-dimensions. The images captured minuscule extensions produced by the circulating T cells to reach across the openings in the vessel walls to liver cells.

The scientists have named it the trans-endothelial hepatocyte-lymphocyte interaction (TEHLI).

"TEHLI appears to be unique to the liver," Bertolino said. "This is the first recorded observation of this event in the body.

"Generally T cells have to be activated by signals from other specialised cells in the lymph nodes before they are able to cross any vessel walls to invade the surrounding tissue to fight disease.

"This discovery of TEHLI will improve our understanding of how the liver protects itself against diseases such as hepatitis C infection and how we can target the disease during its early stages."

These results suggest that changes to the structure of the cells lining blood vessels which lead to a reduction in the openings required for TEHLI, such as cirrhosis and old age, could affect an individual's immune response.

"In a parallel study the group has shown that following injury caused by hepatitis, the liver protects itself from further damage from attack by T cells by closing the openings present in the cells of the blood vessel walls," he said.

"Our study suggests that regulating the size and number of these openings might be used as a strategy to prevent chronic liver disease or regulate liver damage by the immune system."

The results will be published in the November issue of Hepatology and Journal of Hepatology.

Source: Centenary Institute