Abstract
In the intrahepatic lymphocyte fraction (IHL) of mice whose livers have been perfused by Ca++ and Mg++ free Hank's balance salt solution, flow cytometric analysis reveals various cells similar to those found in the spleen (CD3+ cell, CD4+ cell, CD8+ cell, αβTCR+ cell, γδTCR+ cell, Thy1.2+ cell, B220+ cell and asialo-Gm1+ cell). The cytotoxic activity against YAC-1 cells in IHL is significantly higher than that in spleen cells. Furthermore, IHL has cytolytic activity against syngeneic thymoma BW5147 cells which is not found in spleen cells. Both cytotoxic activities of IHL are greatly weakened by the pretreatment of IHL with anti asialo-Gml Ab and rabbit complement. During liver regeneration after a partial hepatectomy, the parcentages of lymphocyte subsets of IHL such as αβTCR+ cells, γδTCR+ cells and asialo-Gm1+ cells transiently increase 2 days after the partial hepatectomy and their cytotoxic activities against YAC-1 and BW5147 cells also reach a peak at that time. It is well known that the peak of mitotic index in regenerating parenchymal liver cells peaks 2 days after a partial hepatectomy and that the number of Pit cells peaks 10 to 14 days after. Compared with the time for reaching the highest mitotic index in regenerating parenchymal liver cells, the proliferation of Pit cells comes very late. It has not been clear which proliferation process in parenchymal liver cells is suppressed by activated Pit cells. Our findings in this paper reveal that the percentages and the cytotoxic activities of asialo-Gm1+ cells in IHL reach their peak 2 days after an operation. This strongly suggest that Pit cells suppress the proliferation of parenchymal liver cells at the primary stage of liver regeneration.
