PDCD1 and neoplasm: Inulin, as a common dietary fiber, can effectively regulate the intestinal microbiota as an oral gel and enhance the anti-tumor effect of ICIs (such as α-PD-1). Oral inulin gel therapy can increase the abundance of key symbiotic microorganisms and their SCFA metabolites in the intestine, and enhance the systemic response of memory T cells. Specifically, the treatment increased the recall response of interferon -γ+CD8+ T cells and promoted the formation of stem cell-like T cytokine -1+PD-1+CD8+ T cells in the TME.