C3 and lupus nephritis: Histopathologic assessment revealed proliferation of mesangial cells, with deposition of IgG and complement components C3 and C1q (all characteristic features of lupus nephritis) in the glomerulus of 7-month-old HOIL-1LΔRING1/ΔRING1 female mice (Figure 2, D and E, and Supplemental Figure 2, B and C).