Deposition of ER4G, rat C1q, C3, C6, and C5b-9 in kidney biopsy specimens. Groups of four rats each were injected IV 500 mg/kg of IVIG and 30 minutes later 0.5 mg/kg anti-Thy 1 MoAb, ER4G. Kidney biopsies were performed 10 minutes, 30 minutes, and 24 hours after ER4G injection and analyzed by immunofluorescence for the presence of ER4G and rat complement components. The extraglomerular staining observed for C3 is frequently encountered in kidney sections of adult rats and not related to the anti-Thy 1 injection. Magnification was 250:1 for all micrographs.