Displays several functions associated with host defense: it promotes agglutination, bacterial capsular swelling, phagocytosis, and complement fixation through its calcium-dependent binding to phosphorylcholine. Binds 2 calcium ions per subunit. Homodimer; disulfide-linked. It is not known if it assembles into a pentraxin (or pentaxin) structure. Pentaxins have a discoid arrangement of 5 non-covalently bound subunits. Is initially detected at the late tail bud stage when the liver appears. Cys-89 or Cys-223 or Cys-236 could be involved in interchain disulfide linkage. Belongs to the pentraxin family. No more Christmas pudding? - Issue 30 of January 2003