Complement studies in membrano-proliferative glomerulonephritis.

Detailed studies of the complement system were carried out in fifteen patients with membranoproliferative glomerulonephritis. The findings of reduced levels of C3 and C7 and of circulating breakdown products of C3 in fresh plasma suggested complement activation. Low C3 levels were associated with the presence of a serum factor (the C3 nephritic factor C3NeF) which was capable of breaking down C3 in normal serum . Metabolic studies using radioactive iodine labelled C3 showed no evidence of accelerated breakdown of parenterally administered C3 suggesting that hypocomplementaemia is either maintained by diminished C3 synthesis or that accelerated catabolism is occurring in a pool that does not freely exchange with parenterally given C3. The C3 nephritic factor has so far only been identified in patients with membranoproliferative nephritis and is therefore of major diagnostic significance in patients with glomerular disease.