C-reactive protein (CRP) is a calcium-dependent pentraxin family protein synthesized primarily in the liver and secreted into circulation as part of the acute-phase response. It exists physiologically as a homopentameric ring composed of five identical ~23–25 kDa subunits, giving a native molecular mass around 115–120 kDa. Functionally, CRP binds phosphocholine on pathogens/damaged cells, activates complement, and promotes phagocytic clearance—serving as a soluble pattern-recognition molecule. Native CRP is purified from human biological fluids, whereas recombinant CRP is expressed in HEK293 or E. coli systems for assay and mechanistic studies. It is extensively used in immunology, cardiovascular research, inflammation modeling, and diagnostic assay development. Research-grade preparations are typically supplied as lyophilized powder.
C-Reactive Protein (CRP)
| CAS No: | 147516-85-6 |
| Synonyms: | C-reactive protein, pentraxin-related, CRP, Pentraxin-1, PTX-1, Pentraxin-related protein |
Product Summary
Function
CRP is a pattern-recognition molecule of innate immunity and a classical acute-phase biomarker. CRP concentrations increase rapidly during inflammation and fall once the stimulus resolves. Below are its key functions:
- Recognizing phosphocholine on microbes and damaged cells.
- Promoting opsonization, agglutination, and phagocytosis.
- Activating the classical complement cascade via C1q binding.
- Facilitating clearance of apoptotic/necrotic material.
Mechanism of Action
During acute inflammation, injured or infected tissues release IL-6, which triggers CRP synthesis in hepatocytes. CRP binds phosphocholine-containing ligands on pathogens or damaged membranes. The ligand-bound CRP directly binds C1q, the recognition component of the classical complement cascade, inducing a regulated complement response. CRP-opsonized particles interact with immune cells and lead to phagocytosis, anti-inflammatory cytokine modulation and efficient disposal of apoptotic debris (efferocytosis).
Applications in Scientific Research
- Immunology & inflammation studies: widely used as a quantitative surrogate marker of cytokine-driven inflammation, particularly IL-6 axis activation.
- Assay development & analytical calibration: commonly used as reference analytes for validating immunochemical detection platforms (ELISA, WB, and immunoassay).
- Host-defense mechanism research: used as a model molecule to dissect antibody-independent immune defense pathways.
- Cardiovascular, autoimmune (infection immunity and tumor immunity), and rheumatology research: studies of chronic low-grade inflammation, a hallmark of many non-infectious diseases.
- Cell-damage recognition & clearance models: CRP plays a critical role in studies of efferocytosis—the removal of apoptotic or necrotic cells.
- Structural biology & protein conformation research: Because CRP can transition from pentameric CRP (pCRP) to monomeric CRP (mCRP), it is widely used to study structure–function relationships.
- Biosensor, nanotechnology, and POCT development: CRP is one of the most frequently selected analytes for translational diagnostic engineering.
Packaging & Storage
- Sources: Recombinant or human biological fluids.
- Available as lyophilized powder.
- Store at 2–8 °C.
References
- Zhou H-H, et al. 2024: C-reactive protein: structure, function, regulation, and role in clinical diseases, Front Immunol. 15: 1425168.
- Salazar J, et al. 2014: C-reactive protein: An in-depth look into structure, function, and regulation, Int Sch Res Notices 2014: 653045.
- Mouliou DS. 2023: C-reactive protein: Pathophysiology, diagnosis, false test results and a novel diagnostic algorithm for clinicians, Diseases 11(4): 132.
- Mantovani A, et al. 2008: Pentraxins in innate immunity: from C-reactive protein to the long pentraxin PTX3, J Clinical Immunol. 28(1): 1-13.
- Fornai F, et al. 2016: The inflammatory protein pentraxin 3 in cardiovascular disease, Immun Ageing 13: 25.
- Thiele JR, et al. 2015: Targeting C-reactive protein in inflammatory disease by preventing conformational changes, Mediators Inflamm. 2015: 372432.
- Napoli MD, et al. 2005: Evaluation of C-reactive protein measurement for assessing the risk and prognosis in ischemic stroke: A statement for health care professionals from the CRP pooling project members, Stroke 38(6): 1316-29.
- Owczarek AJ, et al. 2025: Pentraxin-3 and C-reactive protein plasma levels predict survival in older adults with or without metabolic syndrome – results of the PolSenior2 substudy, Immun Ageing 22: 16.
- Bousquet E, et al. 2023: High levels of C-reactive protein with low levels of pentraxin 3 as biomarkers for central serous chorioretinopathy, Ophthalmology Sci. 3(3): 100278.
- Staubli SM, et al. 2019: The role of CRP and pentraxin 3 in the prediction of systemic inflammatory response syndrome and death in acute pancreatitis, Sci Rep 9: 18340.
- Rajab IM, et al. 2020: How C-reactive protein structural isoforms with distinctive bioactivities affect disease progression, Front Immunol. 11: 2126.
- Ngwa DN, et al. 2022: IL-6 regulates induction of C-reactive protein gene expression by activating STAT3 isoforms, Mol Immunol. 146: 50-56.
- Inforzato A, et al. 2012: Pentraxins in humoral innate immunity, Adv Exp Med Biol. 946: 1-20.