Pentraxins are a superfamily of acute phase reactants characterised by a pentameric structure. The C-reactive protein (CRP) and serum amyloid P-component (SAP) are well-characterised short pentraxins, wich are produced in the liver in response to inflammatory mediators. 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 to man.

Human PTX3 encodes a 381 amino acid, 45 kDa secretory glycoprotein with a 162 amino acid N-terminal extension and a 202 amino acid C-terminal pentraxin domain. The protein is locally produced and released by a variety of cell types including macrophages, neutrophils, myeloid-derived mesangial cells, synovial cells, smooth muscle cells, alveolar epithelium, and glial cells.

PTX3 is secreted in response to recognition of microbial moieties and inflammatory signals. During the early phases of inflammation, neutrophils are present abundantly. Neutrophils represent a major source of PTX3. PTX3 levels increase rapidly under conditions of tissue damage or infection. For example, in acute myocardial infarction with ST elevation, PTX3 achieves a peak in 6-8h, compared to CRP with 36-48h.

PTX3 has a dual role in the regulation of the innate immune response. Via its C-terminal pentraxin domain, immobilized PTX3 will bind complement component C1q to induce classical complement activation. However, fluid-phase PTX3 inhibits classical complement activation. Furthermore, PTX3 participates in the clearance of apoptotic cells.

The level of plasma PTX3 in healthy individuals is 2 ng/ml, whereas in patients suffering from myocardial infarction plasma PTX3 levels up to 7 ng/ml, and in patients suffering from severe dengue virus infections plasma PTX3 levels up to 148 ng/ml have been reported.

Special features of the assay:

• Human pentraxin 3 ELISA has a standard curve of 37.5 to 5000 pg/ml
• Detection level of 37.5 pg/ml
• Useful for plasma
• No cross reactivity for CRP and SAP

Useful marker for:

• Systematic inflammatory response syndrome
• Septic shock
• Glomerulonephritis
• Myocardial infarction
• Rheumatoid arthritis
• Atherosclerosis
• Small vessel vasculitis
• Psoriasis

Also available:

More information on Acute Phase proteins

References:

1. Bussolati B et al; The long pentraxin PTX3 is synthesized in IgA Glomeruslonephritis and activates mesangial cells. J Immunol  2003, 170: 1466
2. Jaillon S et al; The humoral pattern recognition receptor PTX3 is stored in neutrophil granules and localizes in extracellular traps. J Exp Med 2007, 204: 793
3. Jaillon, S et al; Endogenous PTX3 translocates at the membrane of late apoptotic human neutrophils and is involved in their engulfment by macrophages. Cell Death Differ 2009, 16: 465
4. Fazzini F et al; PTX3 in small-vessel vasculitides. An independent indicator of disease activity produced at sites of inflammation. Arthritis Rheum 2001, 44: 2841
5. Peri, G et al; PTX3, a prototypical long pentraxin, is an early indicator of acute myocardial infarction in humans. Circulation 2000, 102: 636
6. Inforzato A et al; Structure and function of the long pentraxin PTX3 glyosidic moiety: fine- tuning of the interaction with C1q and complement activation. Biochem 2006, 45: 11540