Although the direct link between gut microbiome in young melanoma patients and reduced anti-PD1 efficacy, in particular, remains unclear, it can be observed that the members of the Bacteroides fragilis, Clostridium strains that are more prevalent in younger people control systemic inflammation by inducing FOXP3-positive Treg differentiation, production of interleukin-10 and transforming growth factor β [88,89]. Here, PDCD1 is linked to melanoma.