C-reactive protein was discovered in by WS Tillett and T Francis Jr who published in 1930 a paper demonstrating the reaction of a “non-protein material” with serum from patients with pneumonia. The authors discussed several potential explanations for their findings, including anamnestic immune response causing the rapid production of what they named “anti-C precipitins”. 1 We now know that these “precipitins” are a somatic protein encoded by the CRP gene at 1q23.2 and are part of innate immunity rather than a memory response; it is an ancient, highly conserved protein.
The 120kDa pentameric protein secreted by hepatocytes in response to IL-6 and is a member of the pentraxin family, it is used clinically as a marker of inflammatory response.
Biological function
Despite the lack of love paid to it by most medical curricula, CRP does actually have some biological activity. Unfortunately, most of this activity is yet to be elucidated. Its classical role is associated with the antibody like behaviour against the pneumococcal C-polysaccharide (specifically its phosphorylcholine moitey) identified in the early research.
The protein can activate the classical complement pathway as leads to opsonisation and phagocytosis of encapsulated bacteria that would otherwise not be cleared by the immune system.
Further reading
- Tillett WS, Goebel WF, Avery OT. CHEMICAL AND IMMUNOLOGICAL PROPERTIES OF A SPECIES-SPECIFIC CARBOHYDRATE OF PNEUMOCOCCI. J Exp Med. 1930 Nov 30;52(6):895–900. doi:10.1084/jem.52.6.895
- Zhou HH, Tang YL, Xu TH, Cheng B. C-reactive protein: structure, function, regulation, and role in clinical diseases. Front Immunol. 2024 Jun 14;15:1425168. doi:10.3389/fimmu.2024.1425168
Footnotes
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Tillett WS, Francis T. SEROLOGICAL REACTIONS IN PNEUMONIA WITH A NON-PROTEIN SOMATIC FRACTION OF PNEUMOCOCCUS. Journal of Experimental Medicine. 1930 Oct 1;52(4):561–71. doi:10.1084/jem.52.4.561 ↩