 Vampire is 2.0? The ethical quandaries of young blood infusion in the quest for eternal life. In an episode of the TV series Silicon Valley, entitled The Blood Boy, a tech guru hires a young assistant from whom to transfuse pints of blood in an attempt to slow down his aging. The restoration of youth by bathing in or drinking the blood of youth is a centuries-old trope, leading back at least to the futile attempt of ailing Pope Innocent VIII, who in the 1490s failed to live up to his name by apparently drinking the blood of three 10-year-old boys, who, though a bargain costing only one duke out of peace, died in the process. Might there be something to it, though? Though young blood did not have a significant impact on lifespan, otherwise infusing the blood of young animals into old did have rejuvenating effects on multiple organs, similar to full-blown parabiosis, as I talked about in the last video. In fact, not only does the infusion of young mouse blood improve age-related cognitive dysfunction in old mice, young human blood, taken from embolical cords, worked too, in mice engineered to not reject the foreign tissue. This led to ongoing clinical trials offering weekly infusions of blood products from young donors to patients with mild to moderate Alzheimer's disease. But there may be an easier way. Yes, the injection of blood from young mice into old can improve memory and learning, suggesting there's some kind of restorative youth factor. But the injection of blood from old mice into young can worsen memory and learning, suggesting that instead there's some sort of debilitating aging factor. Or maybe the old blood is just diluting the revitalizing factor in the young mouse, or for that matter, maybe the young blood is diluting the debilitating factor in the old mouse. The fact that old blood appears to make things worse more than young blood makes them better suggests maybe the latter is the case, but you don't know until you put it to the test. Ready for a mind-blowing shift in perspective? Instead of infusing young blood into old mice, researchers at UC Berkeley just diluted the blood of old mice by siphoning off the plasma, the liquid portion of the blood, and essentially replacing half of it with water. If the regeneration seen in heterochronic parabiosis and blood transfusions were due to some fountain of youth factor in young blood, then nothing should happen, right? But if all the young blood was doing was diluting some debilitating aging factor, then the water should work just as well, and it did. The rejuvenation in the liver was similar to parabiosis or transfusion, and in the muscles and the brain it was even better. So most, if not all the benefits, could be replicated by simple dilution, including an improvement in cognitive capacity. That's good news, since there's already an FDA-approved procedure in use today, known as therapeutic plasma exchange. It's usually used to filter out toxins or autoimmune antibodies, but why not try using it to try to dilute old blood to treat Alzheimer's disease? And that's exactly what researchers did. Hundreds of Alzheimer's patients were randomized with therapeutic plasma exchange procedure, or a placebo sham procedure, and though it didn't seem to help those with mild Alzheimer's disease, those with moderate Alzheimer's randomized to the real procedure experienced about 60% less cognitive and functional decline over a period of 14 months. This is in stark contrast to mainstay treatments for Alzheimer's, like the drug-maman team that can help with symptoms, but don't actually change or alter the course of the disease. And the added advantage over blood transfusions, as a director of an Institute of Biomedical Ethics put it, there's something peculiar about the old literally feeding on the young.