Pentraxins are a superfamily of acute phase reactants charactarized by a pentamericstructure. The C-reactive protein (CRP) and serum amyloid P-component (SAP) are wellcharactarizedshort Pentraxins, which are produced in the liver in response to inflammatorymediators. Pentraxin 3 (PTX3), also known as Tumor necrosis factor-Stimulated Gene 14(TSG-14), is the prototypic long Pentraxin, with a high degree of conservation from mouse toman.Human PTX3 encodes a 45 kDa secretory glycoprotein with a 162 amino acid N-terminalextension and a 202 amino acid C-terminal Pentraxin domain. The protein is locally producedand released by a variety of cell types including macrophages, neutrophils, myeloid-derivedmesangial cells, synovial cells, smooth muscle cells, alveolar epithelium, and glial cells.PTX3 is induced in response to either inflammatory cytokines interleukin-1 β (IL-1 β) andtumor necrosis factor α (TNFα) or the selected associated molecular patterns (PAMPs).PTX3 has a dual role in the regulation of the innate immune response. Via its C-terminalPentraxin domain, immobilized PTX3 will bind complement component C1q to induceclassical complement activation. However, fluid-phase PTX3 inhibits classical complementactivation. Furthermore PTX3 participates in the clearance of apoptic cells.PTX3 is elevated in critically ill patients, with a gradient from systematic inflammatoryresonse syndrome to septic shock, and in several other diseases, such as mycocardialinfarction, rheumatoid arthritis, atherosclerosis, small vessel vasculitis and psoriasis.Furthermore serum levels of PTX3 are higher in preeclamsia compared with normalpregancies.