Promotion of microglia-mediated clearance of Aβ is dependent on Aβ antibodies in IVIG. The depletion of Aβ antibodies from IVIG significantly compromised the IVIG-promoted microglia-mediated Aβ clearance (A, n = 5-6, p < 0.05) as imaged in the subiculum (B). Preincubation of brain sections with 20 μM IVIG followed by wash out of any unbound IVIG prior to addition of exogenous primary microglia conserved microglia-mediated Aβ clearance (A, B, n = 5-6, p < 0.001) that did not significantly differ from the ex vivo incubation in the presence of IVIG throughout the assay (n = 5-6, p > 0.05). Dotted line represents the Aβ immunoreactive area in intact hippocampal brain sections incubated without microglia. The statistical significance of Aβ clearance in comparison to intact brain section incubated without microglia is shown as asterisks below the dotted line, indicating the respective p-values. Scale bar 100 μm.