Microglia activation following Aβ infusion. WT and IL1raKO mice infused with Aβ or vehicle for 28 days were sacrificed on day 42 (n = 5–10 mice/group survived for analysis). Brains were bisected and the right side of the brain was processed for immunohistochemistry while the left hippocampus was dissected and used for biochemical analysis. A) Levels of the pro-inflammatory cytokine IL-1β were significantly higher in IL1raKO mice infused with Aβ compared to WT mice infused with Aβ. B) TNFα levels also showed a stronger upregulation in Aβ-infused IL1raKO mice compared to Aβ-infused WT mice. C) F4/80 immunostaining for activated microglia also revealed a significant increase in IL1raKO mice infused with Aβ versus WT mice infused with Aβ. Representative photomicrographs of F4/80-positive microglia in the hippocampus of a D) WT mouse infused with Aβ, and E) IL1raKO mouse infused with Aβ. Arrowheads point to microglia cell bodies. Bar in D-E = 50 μm (error bars = SEM; * Significantly different, p < 0.01; ***Significantly different, p < 0.001).