C3 and Alzheimer disease: Activation of the neuronal complement in AD brain is supported by the identification of several initial and terminal proteins of complement cascade, including complement 1q (C1q) [26, 28, 31, 32, 59, 60, 66, 70, 73], complement 1s (C1s) [32], complement 1r (C1r) [32], complement 3 (C3) [26, 28, 31, 32, 59, 60, 66, 73], complement 4 (C4) [26, 31, 32, 59, 60, 66, 73], complement 5 (C5) [32], complement 7 (C7) [32], and complement factor H [32, 59] in AD plaques.