COMPLEMENT C6 AND C2 BIOSYNTHESIS IN SYNGENEIC PVG C(-) AND PVG/C(+) RAT STRAINS/

A PVG rat strain with total deficiency of C6 and partial deficiency of C2 (PVG/c(-)), and a syngeneic control strain (PVG/c(+)), were used t o study the production of extrahepatically synthesized complement. Liv ers of complement deficient rats were transplanted in sufficient rats (Tx-L), The C6 and C2 levels in Tx-L rats declined within 2 days to 25 % and 30%, respectively, and remained stable for more than 6 weeks. To investigate the contribution of C6 synthesis by the liver, C6 suffici ent livers were grafted in deficient rats (Tx + 1). After an initial i ncrease, with maximum C6 levels of 119% at 10 days following transplan tation, the C6 levels decreased gradually and C6 was no longer detecta ble 28 days after transplantation. This decline in C6 levels was depen dent on antibody production against C6. No significant change in the C 3, C4, factor H and factor B levels was observed. Expression of C6 mRN A in the grafted PVG/c(+) sufficient liver was comparable to the expre ssion of C6 mRNA in control PVG/c(+) livers while C6 mRNA expression i n the transplanted PVG/c(-) liver and the control PVG/c(-) liver was l ower, In conclusion, it was demonstrated in vivo that not only C6 but also C2 is synthesized extrahepatically in PVG/c rats.