Activation of the complement system in different forms of glomerulonephritis

The complement system may be activated by two pathways, the classical and the alternate. To evaluate their respective participation in different forms of glomerulonephritis, the plasma values of C3, C4, C3PA, C1q and properdin were determined in 70 patients. In systemic lupus erythematosus (LED), acute poststreptococcal glomerulonephritis (AGN) and septicemia the classical pathway appears to be mainly involved, whereas the amplification loop and the alternate pathway seem to be of secondary importance. By contrast, in membranoproliferative glomerulonephritis (MPGN) the alternate pathway plays a major role. However, the present data suggest that activation of the classical pathway may often be involved as well. In minimal change glomerulonephritis no signs indicating involvement of the complement system were apparent. Follow-up observation demonstrated a correlation between decreases in plasma complement concentrations and the clinical severity of the primary disease in LED, AGN and septicemia, but not in MPGN.