Integrated single-cell and spatial transcriptomic profiling in ALS uncovers peripheral-to-central immune infiltration and reprogramming.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder marked by progressive motor neuron (MN) degeneration in the brain and spinal cord. Although neuroinflammation is increasingly recognized as a hallmark of ALS, the precise molecular programs linking immune responses to MN pathology remain poorly defined. Using an integrated approach that combines single-cell and bulk RNA sequencing with spatial proteogenomics, we characterized both shared and distinct immune dynamics in peripheral blood and spinal cord tissues from patients with sporadic ALS and those carrying C9orf72 repeat expansions. Our analysis revealed broad immune remodeling in C9orf72 ALS, ALS subtype-specific and progression-associated differences in monocyte activation and antigen-experienced CD8 effector memory T cells with clonal features consistent with antigen-driven responses. Spatial mapping revealed complement activation and lipid-programmed myeloid states converging at sites of MN loss and TDP-43 pathology. Together, these findings connect peripheral and central immune alterations to ALS heterogeneity and highlight stratified immunomodulation as a potential therapeutic strategy.