 Pentraxins are characterised by calcium dependent ligand binding and a distinctive flattened β-jellyroll structure similar to that of the legume lectins.The name "pentraxin" is derived from the Greek word for five (penta) and axle (axis) relating to the radial symmetry of five monomers forming a ring approximately 95Å across and 35Å deep observed in the first members of this family to be identified.The "short" pentraxins include Serum Amyloid P component (SAP) and C reactive protein (CRP).