The disease-enhancing effect of JL-1 is dependent on glomerular C1q. (A) Immunofluorescence analysis of anti-GBM antibody deposition and C1q deposition for the C1q-fixing anti-GBM preparation in WT and C1q–/– mice and the non–C1q-fixing anti-GBM preparation in WT mice. The images show the linear IgG fixation for both anti-GBM preparations, but only linear fixation of C1q for the rabbit anti-GBM preparation. Only some mild mesangial C1q positivity can be observed in the mice given sheep anti-GBM. Original magnification, ×400. (B) Groups of WT mice were injected with either the C1q-fixing or the non–C1q-fixing anti-GBM preparation and coinjected with JL-1, control, or PBS, and albuminuria was determined.