CR1, one of the most well-established AD genes [52], was a member of the unique APOE ε2/ε3 AD co-expression network in our study which also contained C4A and C4B. CR1 is a known receptor for C1q as well as C4A and C4B, and can bind to C1q and C4B simultaneously [53]. This evidence concerns the gene APOE and Alzheimer disease.