Here, we present a new mouse model expressing the human proteins CR1 and CR2 that will be of value to study of an array of human diseases including Alzheimer’s disease [3, 8, 9, 12, 27, 34, 36, 41, 72], Systemic Lupus Erythematosus [5, 13, 29, 35, 37, 48, 52, 53, 60, 65, 75, 78, 82] and infections such as malaria [4, 37, 71, 83]. This evidence concerns the gene CR2 and early-onset autosomal dominant Alzheimer disease.