A recent extensive study involving various ethnic groups has revealed that approximately 20% to 30% of individuals carry a specific immune-related gene variant, HLA-DRB1*04, which appears to offer protection against Alzheimer’s and Parkinson’s diseases. These individuals showed an 8% to 15% lower risk of developing these neurodegenerative conditions and exhibited fewer abnormal brain proteins associated with these diseases, such as tau tangles. The findings, published in PNAS, could have implications for the development of new vaccines targeting these diseases. Alzheimer’s and Parkinson’s are characterized by the loss of specific brain neurons and the accumulation of abnormal proteins, and this study suggests that immune genes may play a role in their development. Researchers hope to develop immunotherapies or vaccines based on these gene variants to delay disease onset or progression.