Clinical studies have demonstrated that in immunotherapy resistant melanoma patients, combining FMT with immune checkpoint inhibition therapy significantly increases CD8+ T cells, CD4+ T cells, and activated DCs within the TME, and upregulates Th1 cytokines such as IFN-γ and IL-12, thereby improving the body’s response rate to PD-1/CTLA-4 inhibitors [231, 232]. Here, PDCD1 is linked to melanoma.