We investigated the functions of complement 5a (C5a) and its receptors, C5aR1 and C5aR2, in forming the C5a-C5aR1 and C5a-C5aR2 signaling axes in the immune TME of pancreatic ductal adenocarcinoma (PDAC). The gene discussed is C5; the disease is pancreatic ductal adenocarcinoma.