C3 and lupus nephritis: Placebo-treated substudy participants’ clinical and immunological characteristics collected at entry were as follows: disease duration 0–20 years; 100% with presence of anti-ANA antibodies; 67% with presence of anti-dsDNA antibodies; 10% with presence of anti-Sm antibodies; 30% with anti-RNP antibodies; 69% with low C3 or C4; and 17% with lupus nephritis (Table 1).