The long pentraxin PTX3 as a key component of humoral innate immunity and a candidate diagnostic for inflammatory diseases.

The innate immune system is composed of a cellular arm and a humoral arm. Components of the humoral arm include members of the complement cascade and soluble pattern recognition molecules (PRMs). These PRMs recognize pathogen-associated molecular patterns and are functional ancestors of antibodies, playing a role in complement activation, opsonization and agglutination. Pentraxins consist of a set of multimeric soluble proteins and represent the prototypic components of humoral innate immunity. The prototypic long pentraxin PTX3 is highly conserved in evolution and produced by somatic and innate immune cells after proinflammatory stimuli. PTX3 interacts with a set of self, nonself and modified self ligands and exerts essential roles in innate immunity, inflammation control and matrix deposition. In addition, translational studies suggest that PTX3 may be a useful biomarker of human pathologies complementary to C-reactive protein. In this study, we will review the general functions of pentraxins in innate immunity and inflammation, focusing our attention on the prototypic long pentraxin PTX3.