Inosine, produced by Akkermansia muciniphila and Bifidobacterium pseudolongum, has been reported to improve ICI efficacy by enhancing tumor antigen presentation via IFNγ and TNFα pathways, activating T cells through adenosine A2A receptor signaling, and serving as an alternative carbon source for CD8+ T cells under metabolic stress [58,59,60]. The gene discussed is CD8A; the disease is neoplasm.