Furthermore, they performed fecal microbiota transplantation experiments in germ-free mice, in which they showed that germ-free mice transplanted with stool samples from patients who responded to anti-PD-1 and anti-PD-L1 therapy had a significantly reduced tumor growth and improved responses to anti-PD-1 and anti-PD-L1 therapy, coupled with a higher density of CD8+ T cells. Here, PDCD1 is linked to neoplasm.