PDCD1LG2 and neoplasm: Although previous studies have demonstrated that gut microbiome can modulate local immune environment directly or indirectly through their metabolites, such as acetate, short‐chain fatty acids, and butyrate,2 there are some detailed mechanisms remain unknown, such as which effector molecular from C. cateniformis and how it regulates immune cells (DCs and T cells) function by affecting endogenous expression of PD‐L2/RGMb from gut to dLNs and tumor microenvironment (Figure 1).