C3 and Alzheimer disease: The neuroprotective properties of another complement factor generated from C1q, namely, C3, have also been investigated; a complement C3-deficient amyloid precursor protein (APP) transgenic AD mouse model (APP; C3(−/−)) exhibited accelerated plaque burden in the cortex and hippocampus, increased plasma Aβ levels, and significant hippocampal neuronal loss [97].