Zanjani et al. showed that C3 localized surrounding β-amyloid plaques in early stages of Alzheimer’s disease, when an important loss of synapsis takes place [51], and other authors have demonstrated a modulatory role of C3 on amyloid pathology in animal models of Alzheimer’s disease [52, 53]. Here, C3 is linked to early-onset autosomal dominant Alzheimer disease.