**2. Molecular structure of CRP**

Entrez Gene summary for CRP the protein encoded by this gene belongs to the pentaxin family. It is involved in several host defense related functions based on its ability to recognize foreign pathogens and damaged cells of the host and to initiate their elimination by interacting with humoral and cellular effector systems in the blood. Consequently, the level of this protein in plasma increases greatly during acute phase response to tissue injury, infection, or other inflammatory stimuli[12]. It is induced by IL1/interleukin-1 and IL6//interleukin-6

UniProtKB/Swiss-Prot: CRP\_HUMAN, P02741 Size: 224 amino acids; 25039 Da Cofactor: Binds 2 calcium ions per subunit Subunit: Homopentamer. Pentaxin (or pentraxin) have a discoid arrangement of 5 noncovalently bound subunits Subcellular location: Secreted Mass spectrometry: Mass=23028; Method=MALDI; Range=19-224; Source=Ref.15; Mass spectrometry: Mass=22930; Method=MALDI; Range=19-223; Source=Ref.15;

C-Reactive Protein 91

**3. Methodology and clinical applications** 

known factors that interfere with CRP production

effectiveness of treatments.

cardiovascular disease [24].

diseases [28].

like hs-CRP, along with the lipid profile [27].

CRP is used mainly as a marker of inflammation. Apart from liver failure, there are few

Measuring and charting CRP values can prove useful in determining disease progress or the

Blood, usually collected in a serum-separating tube, is analyzed in a medical laboratory or at the point of care. Various analytical methods are available for CRP determination, such as ELISA (Enzyme-linked immunosorbent assay ELISA can perform other forms of ligand binding assays instead of strictly "immuno" assays, though the name carried the original "immuno" because of the common use and history of development of this method. The technique essentially requires any ligating reagent that can be immobilized on the solid phase along with a detection reagent that will bind specifically and use an enzyme to generate a signal that can be properly quantified. In between the washes only the ligand and its specific binding counterparts remain specifically bound or "immunosorbed" by antigenantibody interactions to the solid phase, while the nonspecific or unbound components are washed away. Unlike other spectrophotometric wet lab assay formats where the same reaction well (e.g. a cuvette) can be reused after washing, the ELISA plates have the reaction products immunosorbed on the solid phase which is part of the plate and thus are not easily reusable)[19], immunoturbidimetry (Immunoturbidimetric Method This reagent is intended for the in vitro quantitative determination of CRP concentration in serum or plasma on automated clinical chemistry analyzers)[20], rapid immunodiffusion(is a diagnostic test which involves diffusion through a substance such as agar.Two commonly known forms are Ouchterlony double immunodiffusion and radial immunodiffusion) [21], and visual agglutination [22][23] (quantitative slide method and semi quantitative diluted method)

There are two different tests for CRP. The standard test measures a much wider range of CRP levels but is less sensitive in the lower ranges. The high-sensitivity CRP (hs-CRP) test can more accurately detect lower concentrations of the protein (it is more sensitive), which makes it more useful than the CRP test in predicting a *healthy* person's risk for

(hs-CRP) test measures using laser nephelometry. The test gives results in 25 minutes with sensitivity down to 0.04 mg/L [26]. hs-CRP usually is ordered as one of several tests in a cardiovascular risk profile, often along with tests for cholesterol and triglycerides. Some experts say that the best way to predict risk is to combine a good marker for inflammation,

CRP is one of several proteins that are often referred to as acute phase reactants and is used to monitor changes in inflammation associated with many infectious and autoimmune

We should be healthy at the time of the sample collection, without any recent illnesses, infections, inflammation, or other tissue injuries. Since the hs-CRP and CRP tests measure the same molecule, people with chronic inflammation, such as those with arthritis, should

Function: Displays several functions associated with host defense it promotes agglutination, bacterial capsular swelling, phagocytosis (CRP initiates the activation of the complement cascade and binds Fc gamma RI (CD64) and Fc gamma RIIA (CD32a) on phagocytes to activate phagocytic responses) and complement fixation through its calcium-dependent binding to phosphorylcholine. It can interact with DNA and histones and may scavenge nuclear material released from damaged circulating cells [13].

The CRP Entrez gene cytogenetic band located on the first chromosome: 1q21-q23

Ensemble cytogenetic band: 1q23.2 HGNC cytogenetic band: 1q21-q23.

CRP is a 224-residue protein with a monomer molar mass of 25106 Da. The protein is an annular pentameric disc in shape [14][15].

**Figure 1.** Pentameric structure of CRP viewed down the 5-fold symmetry axis. The effector face of the molecule is on the top, while the calcium- and PCh-binding sites are on the opposite 'recognition' face [1]
