PDCD1 and neoplasm: For example, just limited populations of gut bacteria strains, enriched in Ruminococcaceae, Alistipes, Parabacteroides, and Bacteroides from healthy human donor feces, are capable of robustly inducing the accumulation of IFN-γ-producing CD8+ T cells in the gut, enhancing anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)- and anti-PD-1-mediated tumor growth control [34].