Influence of antithymocytic serum on the regenerating activity of the liver after partial hepatectomy in mice.

In experiments on mice the effect of rabbit-anti-mouse antithymocytic serum on the growth of the liver and on the onset of proliferating activity of the liver after partial hepatectomy was studied to elucidate the question of assumed participation of the lymphoid system in the proliferation of hepatic tissue. Administration of three doses of antithymocytic serum (0.1 ml/10 g) by the i.p. route in 24 hour intervals led to a marked increase of the weight of the spleen and increase of DNA synthesis in liver of non-operated mice. Administration of serum 24 hours before partial hepatectomy (PHE) concomitantly with PHE and 24 hours after PHE did not influence substantially the rate of DNA synthesis in the regenerating liver 34 and 48 hours after PHE and did not influence the mitotic index of hepatocytes. In the livers of mice to whom antithymocytic serum was administered proliferation of cells of the lymphocyte series and phagocyte activation occurred. These cells were located in the hepatic sinuses and periportal areas. Antithymocytic serum--contrary to chemical immunosuppressive substances--does not exert an inhibitory action on regeneration of hepatic tissue; alone does not even cause inhibition of the lymphoid system which could exert a negative effect on regeneration of the liver.