Pentraxins in innate immunity: from C-reactive protein to the long pentraxin PTX3.

Pentraxins are a family of multimeric pattern-recognition proteins highly conserved in evolution. Based on the primary structure of the subunit, the pentraxins are divided into two groups: short pentraxins and long pentraxins. C-reactive protein and serum amyloid P-component are classic short pentraxins produced in the liver, whereas the prototype of the long pentraxin family is PTX3. Innate immunity cells and vascular cells produce PTX3 in response to proinflammatory signals and Toll-like receptor engagement. PTX3 interacts with several ligands, including growth factors, extracellular matrix components, and selected pathogens, playing a role in complement activation, facilitating pathogen recognition, and acting as a predecessor of antibodies. In addition, PTX3 is essential in female fertility acting on the assembly of the cumulus oophorus extracellular matrix. Thus, PTX3 is a multifunctional soluble pattern recognition receptor acting as a nonredundant component of the humoral arm of innate immunity and involved in tuning inflammation, in matrix deposition and female fertility. Evidence suggests that PTX3 is a useful new serological marker, rapidly reflecting tissue inflammation and damage under diverse clinical conditions.