PDCD1 and neoplasm: Mice that received stool transplants from responders (Rs) to anti-PD-1 therapy had an improved response to ICI therapy, increased up-regulation of PD-L1 in the tumor microenvironment, improved antigen presentation, and augmented effector T cell function in both the periphery and the tumor microenvironment, when compared with those transplanted with the stool from non-responders (NRs) [12].