The Oklahoma Medical Research Foundation reports on new understanding of the role of ApoE4 in the development of Alzheimer's: "ApoE4 (along with other apolipoproteins) attaches itself to a particular receptor on the surface of brain cells. That receptor, in turn, adheres to a protein known as amyloid precursor protein. The brain cells then transport the entire protein mass inside. Once inside, cutting enzymes - called proteases - attack the amyloid precursor protein. These cuts create protein fragments that, when present in the brain for long periods of time, are believed to cause the cell death, memory loss and neurological dysfunction characteristic of Alzheimer's. ... this new study is the first to connect the process of protein fragment formation to ApoE4. ... ApoE4 apparently interacts better with the receptor than its cousins. This may explain why people who carry the E4 gene have a higher risk of developing Alzheimer's." Differences in susceptibility can be used to discover biochemical mechanisms in just this way - and knowing the mechanisms in this day and age is a fast road to interfering in their progression.