Innate immunity protein that plays several important functions in antimicrobial and antitumor defense systems. Acts as a pattern receptor that binds to murein peptidoglycans (PGN) of Gram- positive bacteria and thus provides bactericidal activity (PubMed:9707603). Forms an equimolar complex with heat shock protein HSPA1A and induces programmed cell death through apoptosis and necroptosis in tumor cell lines by activating the TNFR1 receptor on the target cell membrane (PubMed:21247889, PubMed:26183779). In addition, acts in complex with the Ca(2+)-binding protein S100A4 as a chemoattractant able to induce lymphocyte movement (PubMed:26654597). Mechanistically, this complex acts as a ligand of the chemotactic receptors CCR5 and CXCR3 which are present on the cells of the immune system (PubMed:30713770). Also promotes the activation of lymphocytes that become able to kill virus-infected cells as well as tumor cells by modulating the spectrum of their target-cell specificity (PubMed:28977785, PubMed:29083508). Induction of cytotoxicity on monocyte surface requires interaction with TREM1 receptor (PubMed:25595774, PubMed:28977785). {ECO:0000269|PubMed:21247889, ECO:0000269|PubMed:25595774, ECO:0000269|PubMed:26183779, ECO:0000269|PubMed:26654597, ECO:0000269|PubMed:28977785, ECO:0000269|PubMed:29083508, ECO:0000269|PubMed:30713770, ECO:0000269|PubMed:9707603}. This is the function of Ensembl gene identifier ENSG00000008438 (PGLYRP1, peptidoglycan recognition protein 1).