195: Tiny Shields: Lymphoid Microglia in Alzheimer’s Disease

️ Episode 195: Tiny Shields: Lymphoid Microglia in Alzheimer’s Disease In this episode of PaperCast Base by Base, we explore how a subset of brain immune cells adopts a lymphoid-like program that helps contain inflammation and protect neural circuits in Alzheimer’s disease models. Study Highlights: Using mouse models of amyloid pathology and human Alzheimer’s brain tissue, the authors identify plaque-associated microglia with reduced PU.1 expression that cluster around deposits and express an unexpected set of lymphoid receptors, including CD28. By genetically tuning PU.1 levels specifically in microglia, they show that lowering PU.1 is sufficient to trigger this lymphoid-like transcriptional program, remodel chromatin and generate microglia that compact amyloid plaques, limit tau aggregation and preserve synapses, plasticity and behaviour. These PU.1low microglia display fewer type I interferon and complement signatures, accumulate fewer lipid droplets and extend survival in Alzheimer’s model mice, indicating a broadly neuroprotective state. In contrast, microglia-specific deletion of CD28 amplifies amyloid burden and drives a widespread pro-inflammatory interferon response in the microglial pool, suggesting that a small CD28+ subset exerts outsized control over brain inflammation. Human genetic data further link a PU.1-lowering SPI1 allele with increased abundance of lymphoid-like microglia, supporting the relevance of this protective program in people with Alzheimer’s disease. Conclusion: This work positions PU.1-tuned, CD28-expressing microglia as critical regulators of neuroinflammation and suggests that selectively boosting their lymphoid-style “checkpoint” signals could inspire new immunotherapy strategies for Alzheimer’s disease. Music: Enjoy the music based on this article at the end of the episode. Reference: Ayata P, Crowley JM, Challman MF, et al. Lymphoid gene expression supports neuroprotective microglia function. Nature. 2025. https://doi.org/10.1038/s41586-025-09662-z. License: This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/ Support: If you'd like to support Base by Base, you can make a one-time or monthly donation here: https://basebybase.com/ On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.