C3 and primary membranoproliferative glomerulonephritis: Types I and III MPGN, which exhibit deposits of IgG and C3 on immunofluorescence (IF), are now considered as MPGN caused by IC (IC-MPGN), while type II MPGN, also known as dense deposit disease (DDD), and all the forms with isolated/predominant C3 IF-deposits, are considered as C3G (Figure 1).