BACKGROUND & AIMS:
Chronic infections by hepatotropic viruses such as hepatitis B and C are generally associated with an impaired CD8 T-cellimmune response that is unable to clear the virus. The liver is increasingly recognized as an alternative site in which primary activation of CD8 T cells takes place, a property that might explain its role in inducing tolerance. However, the molecular mechanism by which intrahepatically activated T cells become tolerant is unknown. Here, we investigated the phenotype and fate of naïve CD8 T cells activated by hepatocytes in vivo.
Transgenic mouse models in which the antigen is expressed in lymph nodes and/or in the liver were adoptively transferred with naïveCD8 T cells specific for the hepatic antigen.
Liver-activated CD8 T cells displayed poor effector functions and a unique CD25(low) CD54(low) phenotype. This phenotype was associated with increased expression of the proapoptotic protein Bim and caspase-3, demonstrating that these cells are programmed to die followingintrahepatic activation. Importantly, we show that T cells deficient for Bim survived following intrahepatic activation.
This study identifies Bim for the first time as a critical initiator of T-cell death in the liver. Thus, strategies inhibiting the up-regulation of this molecule could potentially be used to rescue CD8 T cells, clear the virus, and reverse the outcome of viral chronic infections affecting the li
Gastroenterology 135, 135:989-997 (IF: 12.0) (2008)