IVIG promotes microglia-mediated clearance of natively formed Aβ deposits. In an ex vivo assay, neonatal mouse microglial cells were incubated on top of APP/PS1 brain sections. After incubation period of 24 h, the Aβ burden was quantified by Aβ immunostaining. Microglia alone reduced Aβ burden ex vivo (A, C, n = 6-8, p < 0.05) as quantified from the whole hippocampus area. IVIG further promoted microglia-mediated Aβ clearance (A, C, n = 6-8, p < 0.05). The reduction of Aβ was observed as Aβ-free cavities in the brain sections at sites of cultured microglia cell bodies, visualized with DAPI, as exemplified for the subiculum (D). When the ex vivo assay was performed for adult mouse astrocytes, we observed a significant reduction of Aβ burden (B, n = 6-8, p < 0.01), quantified from the whole hippocampus area, but no promotion of Aβ clearance with up to 20 μM IVIG (B, n = 6-8). Scale bars 200 μm (C) and 50 μm (D).