CD8A and neoplasm: Notably, these metabolites display striking context-dependent duality: butyrate can simultaneously augment cytotoxic CD8+ T-cell activity and promote regulatory T-cell expansion; indole derivatives can either sustain antitumor Th1/CTL responses or accelerate tumor growth depending on tissue context; SBAs and TMAO have likewise been reported to exert either immunostimulatory and immunosuppressive functions depending on exposure, receptor usage and tumor type [31–34].