Recent studies reveal novel immune and environmental pathways in Alzheimer's disease. A Washington University study shows T cells contributing to neurodegeneration are activated in lymph nodes outside the brain, offering a target that bypasses the blood-brain barrier. Meanwhile, South Korean researchers restored microglial defenses in mice by blocking the PD-L1 protein, and a US review links ionizing radiation to Alzheimer's-like brain inflammation via the eCIRP molecule.
Role of lymph nodes in T cell activation
- ▪Washington University School of Medicine professor David M. Holtzman, MD, stated that targeting Alzheimer's disease-related immune processes outside the brain could allow treatments to bypass the blood-brain barrier.
- ▪T cells rely on classical dendritic cells type 1 (cDC1) to identify molecular targets, but very few cDC1 cells are found in the brain, suggesting the activation process originates elsewhere.
- ▪A study from Washington University School of Medicine in St. Louis published in Nature Neuroscience on September 3, 2026, found that T cells receive signals from lymph nodes outside the brain that prepare them to enter the brain.
- ▪Washington University School of Medicine researchers suggest that tau protein damage releases brain cell material that travels to neck lymph nodes, where dendritic cells present it to T cells.
Effects of manipulating dendritic cells in mice
- ▪Eliminating dendritic cells from the lymph nodes of mice modeling tau-related damage dramatically reduced brain T cells and brain damage, while the amount of tau tangles remained unchanged.
- ▪Mice with eliminated dendritic cells preserved their cognitive abilities despite the presence of tau tangles, suggesting that suppressing T cell activity could slow Alzheimer's-related cognitive decline.
- ▪Washington University School of Medicine researchers are testing whether interfering with dendritic cell activity in midlife can protect mice against tau-related neurodegeneration.
Targeting PD-L1 in the brain
- ▪In mice used to model Alzheimer's disease, researchers found increased levels of the protein PD-1 in microglia and increased levels of PD-L1 in astrocytes.
- ▪Linus Health chief operating officer Dr. John Showalter noted that delivering antibodies directly into the fluid surrounding the brain and spinal cord is highly risky for human patients.
- ▪A Sungkyunkwan University study in Science Advances showed directly administering an antibody blocking PD-L1 into Alzheimer's model mice brains reduced excessive neuron activity and restored microglial response to damaged areas.
Ionizing radiation and dementia risk
- ▪A review published in Frontiers in Immunology by Hofstra University and Northwell Health researchers suggests that exposure to ionizing radiation triggers biological changes in the brain resembling Alzheimer's disease.
- ▪A meta-analysis of 18 studies by Hofstra University and Northwell Health researchers found an 11 percent increase in dementia risk for every 100 millisieverts of cumulative radiation exposure.
- ▪Hofstra University and Northwell Health researchers identified the molecule eCIRP as a potential link between radiation-induced DNA damage, brain inflammation, and the phosphorylation of tau proteins.
Debatable claims
- ▪Targeting immune processes outside the brain is a viable way to treat Alzheimer's
- ▪Immune-system therapies are more promising for Alzheimer's treatment than traditional amyloid and tau targets
- ▪Suppressing T-cell activity is sufficient to prevent Alzheimer's-related cognitive decline
- ▪Researchers should pursue direct brain delivery of PD-L1 antibodies for Alzheimer's
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