ALS-associated TDP-43 aggregates drive innate and adaptive immune cell activation.

Amyotrophic lateral sclerosis (ALS) is the most common and fatal motor neuron disease. Approximately 90% of ALS patients exhibit pathology of the master RNA regulator, transactive response DNA binding protein (TDP-43). Despite the prevalence TDP-43 pathology in ALS motor neurons, recent findings suggest immune dysfunction is a determinant of disease progression in patients. Whether TDP-43 aggregates elicit immune responses remains underexplored. In this study, we demonstrate that TDP-43 aggregates are internalized by antigen-presenting cell populations, cause vesicle rupture, and drive innate and adaptive immune cell activation by way of antigen presentation. Using a multiplex imaging platform, we observed enrichment of activated microglia/macrophages in ALS white matter that correlated with phosphorylated TDP-43 accumulation, CD8 T cell infiltration, and major histocompatibility complex expression. Taken together, this study sheds light on a novel cellular response to TDP-43 aggregates through an immunological lens.