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; disulfide-linked. Pentraxin (or pentaxin) have a discoid arrangement of 5 non-covalently bound subunits. Two of the five chains form a dimer linked by two interchain disulfide bonds located in the C-terminal heptapeptide and specific to rat CRP. Interacts with FCN1; may regulate monocyte activation by FCN1 (By similarity). Found in plasma. The last two cysteines are involved either in interchain disulfide bonds or in an intrachain bond. Belongs to the pentraxin family. No more Christmas pudding? - Issue 30 of January 2003