Figure 8. Possible association among hepatic mast cells, Foxp3⁺ Tregs and γδ T cells for immune regulation and hepatocellular chimerism.

Under the guidance of SCF/c-Kit signaling, hematopoietic stem/progenitor cells migrate to the liver allografts to induce liver allograft tolerance and simultaneously induce liver regeneration for the replacement of donor with recipient hepatic cells. Foxp3⁺ Tregs may produce IL-9 and SCF to activate hepatic mast cells; in turn, activating mast cells may produce TGF-β1, and IL-2 and/or release histamine by degranulation. TGF-β1 also plays a key role in the generation of IL-17−producing γδ T cells; in turn, IL-17 indirectly attracts Foxp3⁺ Tregs, enhances their suppressor function, and induces IL-9 and SCF production by Foxp3⁺ Tregs. Production of SCF, TGF-β1, and IL-10 also may regulate liver regeneration.