PDCD1 and melanoma: In consistent with the above study, concerning the melanoma patient cohort, Matson et al. revealed that the enrichment of Bifidobacterium longum, Enterococcus faecium, and Collinsella aerofaciens was positively correlated with augmented systemic T cell response, optimized tumor control, and improved immune-potentiating effect of anti-PD1 (Figure 1A) (58).