TLR4 and Alzheimer disease: Results of in vivo studies in a double transgenic (APPswe/PSEN1dE9) mouse model of AD demonstrated a lack of TLR4 resulted in an increased cortical and hippocampal Aβ load, suggestive of a decisive role of TLR4 in the Aβ clearance by microglial cells (Arroyo et al., 2011).