Figure 2

Incubation at pH 2.5 induced artifactual ELISA signal appears to be IgG associated. Panel 2A. Normal sera were collected from nonTg unvaccinated mice, diluted 1:400 and preincubated at either pH 7 (open bars) or pH 2.5 (solid bars) as described in methods. After centrifugation, neutralization and reconstitution of sera volume, the sera were incubated on the ELISA plates coated with human Aβ1–42 for 60 minutes. After washing the plate, anti-mouse gamma chain specific (left) or anti-mouse whole IgG (right) were pipetted into the different wells of plate. Panel 2B. Normal sera from nonTg unvaccinated mice were incubated at pH 7.0 (open bars) or pH 2.5 (solid bars) and then IgG was purified with protein A/G (Pierce) as described in methods. Protein was measured with BCA protein assay Kit (Pierce), and dilutions of the purified IgG were incubated as the indicated concentrations on ELISA plates coated with Aβ1–42. ELISA assays were completed as described in methods. ** P < 0.001 compared to pH 7.0.