[A study on the location of synthetic sites of the fourth and fifth components of the complement system in allogeneic bone marrow chimeras and hepatocyte transplantation chimeras].

In this study, the tissue sites for synthesis of fourth and fifth components of complement (C4, C5) have been investigated by using allogeneic bone marrow chimeras and bone marrow chimeras which were transplanted in addition with hepatocytes. One group of chimeric mice was prepared by transplanting bone marrow cells from C5-sufficient donor mice into irradiated C5-deficient recipients or vice versa, and another group was prepared by transplanting marrow cells from mice which produced high level of C4 into irradiated recipients which were characterized by having low level of C4 or vice versa. The results showed that C4 or C5 antigens were present in the sera of the chimeras only when recipients were strains which were characterized by having high C4 level or were C5-sufficient mice, respectively. These findings indicate that circulating C4 and C5 in the blood are not synthesized primarily by cells that are descendants of bone marrow cells in these chimeric mice. However, when hepatocytes isolated from the C5-sufficient strain were inoculated into the spleens of C5-deficient bone marrow chimeras, detectable amounts of C5 were present in the sera. These results indicate that C5 protein is synthesized and delivered to the blood in vivo by liver cells.