PDCD1 and Huntington disease: Compared to HD, the CRC patients were characterized by decreased α-diversity (Figure S1a-b), distinct β-diversity (Figure S1c) as well as disturbed gut microbiota profiles (Figure S1d-f) consistent with recent studies.14,15 To determine whether and if so, to what extent, gut microbiota has influenced the response to anti-PD-1, we took advantage of avatar mouse models, which were gavaged with a broad-spectrum antibiotic cocktail (ATB) to depleted endogenous microbiota and subsequently humanized with feces from HD or CRC donors using fecal microbial transplantation (FMT).