Intra- and extrahepatic leukocytes and cytokine mRNA expression during liver regeneration after partial hepatectomy in rats

We investigated intra- and extrahepatic leukocytes during liver regeneration after a 70% partial hepatectomy in the rats using flow cytometry and RT-PCR for cytokine mRNA expression. Our study indicated that LFA-1(+++) CD3(+) cell, NK3.2.3(++) T cells, and CD5(+) B cells, which are activated in autoimmune diseases and malignancy in humans and mice, were activated in the early phase of liver regeneration in the liver and the blood after partial hepatectomy in the rats. On measuring cytokine mRNA expression by RT-PCR, only IFN-gamma mRNA was detected in the normal rat liver. IFN-gamma mRNA expression clearly decreased in the liver on day 1 after partial hepatectomy and increased thereafter. IL-2 and IL-4 mRNA were not detected in the liver regardless of hepatectomy. Every cytokine was detected in normal spleen and increased in the early phase after partial hepatectomy. These were also detected in normal thymus; however, IL-2 and IFN-gamma mRNA expressions decreased and IL-4 mRNA expression increased slightly in the early phase after partial hepatectomy. Thus, the immune system dramatically changed both in the liver and elsewhere in the early phase of liver regeneration after partial hepatectomy.