In addition to the relatively common variants, there have been various rare variants of apoE identified, such as apoE3-R136S (apoE3-Christchurch; apoE3-Ch), apoE3-V236E (apoE3-Jacksonville; apoE3-Jac,) and apoE4-R251G [15–19], that are thought to confer some protection against AD pathology. This evidence concerns the gene APOE and Alzheimer disease.