HTT and Huntington disease: Importantly, HD subject immune cells, such as monocytes, macrophages, and B and T cells express mutant huntingtin, which leads to dysfunction characterized by excessive inflammatory cytokine production and altered immune signaling pathways17 correlating with disease status.18,19 Immune reactions in HD appear to result from a combination of extrinsic effects, driven by ongoing neurodegeneration, and intrinsic factors where mutant huntingtin directly alters the behavior of immune cells.