Influence of IVIG on anti-Thy 1 binding and rat C3 deposition on rat glomerular mesangial cells (RMC) in vitro. Cultured RMC were incubated with serial dilutions of IVIgM and IVIgG followed by addition of anti-Thy 1 MoAb, ER4G (1 μg/mL) and 10% normal rat serum. Binding of ER4G (top) and rat C3 (bottom) was analyzed in parallel by FACS. A representative experiment of two performed is shown.