Displays several functions associated with host defense: it promotes agglutination, bacterial capsular swelling, phagocytosis and complement fixation through its calcium-dependent binding to phosphorylcholine. Can interact with DNA and histones and may scavenge nuclear material released from damaged circulating cells (By similarity). Binds 2 calcium ions per subunit. Homopentamer. Pentraxin (or pentaxin) have a discoid arrangement of 5 non-covalently bound subunits. Interacts with FCN1; may regulate monocyte activation by FCN1 (By similarity). Found in plasma. Belongs to the pentraxin family. No more Christmas pudding? - Issue 30 of January 2003