Membrane and soluble pattern recognition receptors: the unique functions of the long pentraxin PTX3

Summary Pentraxin 3 (PTX3), the first long pentraxin identified, is characterized by a C‐terminal pentraxin like domain, showing sequence similarity to C‐reactive protein and serum amyloid P component, coupled with a N‐terminal unrelated portion. PTX3 is made by diverse cell types, including endothelial cells, macrophages and dendritic cells, in response to proinflammatory signals such as interleukin 1, tumor necrosis factor and lipopolysaccharide. It binds different ligands, including Clq, apoptotic cells and microbial mojcties. PTX3 levels are <2 ng/mL in normal subjects but increase in a number of pathological conditions such as autoimmune, infectious and degenerative disorders. Evidence from clinical studies and genetically modified animals suggests that PTX3 plays a role in inflammatory reactions as well as in the regulation of innate resistance to pathogens and female fertility. The results obtained so far indicate that PTX3 is a soluble pattern recognition receptor which plays a non redundant role in female fertility and resistance against selected pathogens.