A. Aβ immunoprecipitation underestimates Aβ. The Aβ signal coming from the lane with direct load of synthetic Aβ1–42 (lane 1) is much higher than the signal coming from the lanes where synthetic Aβ1–42 was added to lysate (lane 4), media (lane 6) or IP buffer (lane 7) and then immunoprecipitated (MWM, molecular weight markers). 4G8 antibody was used for immunoprecipitation; 6E10 antibody was used for immunoblotting. n=3, **p<0.01 B. Treatment of N2a cells over-expressing the human APP Swedish mutation with triton X induces loss of Aβ and APP, as assessed by direct load Western blot. n=3, *p<0.05.