OCCURRENCE OF C3 NEPHRITIC FACTOR AND C4 NEPHRITIC FACTOR IN MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS (MPGN)

One hundred patients diagnosed with hypocomplementaemic MPGN (C3 < 40% ) were studied to determine the presence of C3 nephritic factor (C3NeF ) and/or C4 nephritic factor (C4NeF). Of those studied, 12 were C3NeF- positive, nine were C4NeF-positive and 10 were positive for both C3NeF and C4NeF. In the 10 patients both C3NeF- and C4NeF-positive, a marke d decrease in C3 and C5 levels and a decrease in levels of late compon ents from C6 to C9 were observed. This observation was in contrast to that seen in patients who were either C3NeF- or C4NeF-positive. Patien ts positive for both C3NeF and C4NeF continued to exhibit hypocompleme ntaemia after therapy. Immunofluorescent findings revealed heavy C3 im munoglobulin deposits in the 10 patients who were both C3NeF- and C4Ne F-positive, whereas no such deposits were found in those patients who were either C3NeF- or C4NeF-positive only. When those patients who wer e both C3NeF- and C4NeF-positive were compared with those who were eit her C3NeF- or C4NeF-positive, nephritic syndrome and a poor prognosis were observed more frequently. This study demonstrates a correlation b etween clinical outcome and hypocomplementaemic MPGN. Further investig ations of MPGN as an autoimmune disease are necessary.