( etween lymphocytes (T cells) liver sin...)Interaction between lymph and liver cells may affect immune response

etween lymphocytes (T cells), liver sinusoidal endothelial cells (LSECs) and hepatocytes (liver cells) using electron microscopy. LSECs are highly specialized endothelial cells that line the walls of hepatic sinusoid cells (gossamer-like structures that form the rich capillary network of the liver) and are perforated by fenestrations, or openings. The researchers hypothesized that the fenestrations could provide a portal through which liver cells and T cells could interact or that the interaction could take place across gaps between LSECs.

The study was conducted using mice whose livers had been injected with lymphocytes. The mouse livers were examined with two types of electron microscopy. Analysis of the images showed a large number of intrahepatic lymphocytes (IHLs) that had extensions similar to the dimensions of the fenestrations of the LSECs. These extensions were seen within the fenestrations and were observed to be in contact with minute projections on liver cells (hepatocyte microvilli). There were no observable gaps between LSECs and hepatocyte microvilli did not seem to interact with circulating lymphocytes. Further investigation showed that naïve T cells displayed the same extensions as IHLs and were also able to interact with liver cells through LSEC fenestrations. The authors propose the term "trans-endothelial hepatocyte-lymphocyte interactions" (TEHLI) to describe these interactions.

The discovery of TEHLI is the first demonstration by electron microscopy of the interaction between naïve T cells and liver cells in a living organism, which shows that the liver is an exception to the rule that T cells need to be activated by professional APCs in order to cross the endothelial barrier, and that hepatocytes can function as APCs. In fact, this T cell activation in the liver during early hepatitis C infection may contribute to the impaired immune response seen in chronic hepatitis C.

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Source:John Wiley & Sons, Inc.

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