Human C-reactive protein (CRP) is one of the socalled acute
phase proteins. CRP is produced in liver and its concentration in blood
increases rapidly as a response to inflammation. It is routinely used as a
non-specific marker of inflammation. CRP is a 224-residue protein with a
monomer molecular mass of approximately 25 kDa and pI 6.4 (1-4). It belongs
to pentraxins, an evolutionally conserved family of proteins characterized by
calcium dependent ligand binding and radial symmetry of five monomers
forming a ring around central pore (5). The total mass of the CRP pentamer is
approximately 120 kDa. The precise function of CRP in vivo is still not yet
completely clear, but it has been shown that CRP increases by the secretion of
interleukin-6 produced by for example macrophages and T cells (6). CRP has been
shown to participate in inflammatory as well as innate immunity processes. The
level of CRP in the blood of healthy people is usually low but in infections
caused by bacteria the concentration of CRP can quite easily increase tenfold.
In contrast, infections of viral origin usually result in just a moderate
increase in the level of CRP. Important bioactivities of CRP are
determined by its ability to bind to a variety of ligands, such as damaged cell membranes, apoptotic
cells and fibronectin,
with the highest affinity to phosphocholine residues. When CRP is ligand-bound, it can be recognized by the complement component C1q, which leads to activation of the classical complement pathway. On the other hand, via interaction with the complement factor H, CRP regulates the alternative complement pathway (7).
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