Gegen Qinlian Decoction combined with PD-1 inhibitors boosts immunotherapy for MSS CRC. The treatment enriches gut bacteria like Bacteroides acidificus and alters lipid metabolism (glycerophospholipids/sphingolipids). It also increases CD8+ T cells, enhances IFN-γ/IL-2 expression, and reduces PD-1 levels, reactivating T cells. This microbiome-metabolism-immune approach offers a new strategy for MSS CRC. The gene discussed is PDCD1; the disease is colorectal carcinoma.