Published online Jul 7, 2019. doi: 10.3748/wjg.v25.i25.3123
Peer-review started: March 15, 2019
First decision: April 11, 2019
Revised: April 25, 2019
Accepted: May 18, 2019
Article in press: May 18, 2019
Published online: July 7, 2019
The transplanted liver can modulate the recipient immune system to induce tolerance after transplantation. This phenomenon was observed nearly five decades ago. Subsequently, the liver’s role in multivisceral transplantation was recognized, as it has a protective role in preventing rejection of simultaneously transplanted solid organs such as kidney and heart. The liver has a unique architecture and is home to many cells involved in immunity and inflammation. After transplantation, these cells migrate from the liver into the recipient. Early studies identified chimerism as an important mechanism by which the liver modulates the human immune system. Recent studies on human T-cell subtypes, cytokine expression, and gene expression in the allograft have expanded our knowledge on the potential mechanisms underlying immunomodulation. In this article, we discuss the privileged state of liver transplantation compared to other solid organ transplantation, the liver allograft’s role in multivisceral transplantation, various cells in the liver involved in immune responses, and the potential mechanisms underlying immunomodulation of host alloresponses.
Core tip: The liver not only protects itself from host alloimmune responses, but also modulates alloimmune responses to other simultaneously transplanted solid organs like heart or kidney. The titer of donor specific alloantibodies decreases after liver transplantation, making transplantation of other solid organs possible even in highly sensitized high-risk patients. The immune cells from the liver allograft cross-talk with recipient immune cells and modulate the immune system towards tolerance. The cross-talk between these cells suppress the genes involved in alloimmunity and upregulate the genes involved in tissue repair and metabolism.