Cell-mediated suppression of the fifth component of complement in mice.

Suppression of levels of circulating C5 in (C5- C5+)F1 hybrids by administration of (C5- C5-) parental lymphoid cells in the neonatal period has been accomplished with the three strain combinations tested ((SWR X RIII)F1, (A/He x RIII)F1, and (SWR X DBA/1)F1). Suppression was shown to be specific for C5 and not accompanied by reductions of C1, C2, C6, or other major groups of blood proteins. This demonstrated that the C5 reduction was not due to activation of complement (C) with resultant hypercatabolism of C components. When there was a concurrent chronic GVH reaction induced by lymphoid cells administered to offspring of H-2 incompatible parents, there was usually a resultant hypergammaglobulinemia that was also unrelated to the presence or absence of C5 suppression. Effective suppression required preimmunization of either the cell donor, the mother of the F1 hybrids, or both. This suggests that either two cell types or a single cell plus a humoral factor are required for suppression in this system.