PDCD1 and cancer: Collinsella aerofaciens is usually associated with pro-inflammatory responses and adverse health outcomes, but there are significant exceptions to its favorable response to PD-1/PD-L1 cancer immunotherapy. The glycosylated glyceride compound CaLGL-1 produced by Collinsella aerofaciens has a β -galactofuran sugar head group with acetal and can activate the immune response through the TLR2-dependent signaling pathway. Furthermore, this compound is transformed from plasmalogen, which is synthesized by bacteria, in a low pH environment.