They are accompanied by synaptic loss, neuroinflammation, and neuronal death, and compromise the blood-brain barrier, allowing immune cells to infiltrate the brain parenchyma and interact with glial cells and neurons; all of these factors contribute to disease progression.2 Activated T cells can be found in postmortem brains of different neurological disorders, in AD, particularly in areas with neuronal loss and Tau pathology, i.e., the hippocampus and limbic structures. Here, MAPT is linked to Alzheimer disease.