C-Reactive Protein: Discovery and Nomenclature
C-reactive protein was discovered approximately 50 years prior to 1981 (around 1930) and received its name because it reacts with the C-polysaccharide of Streptococcus pneumoniae to form precipitates in the serum of patients with pneumococcal infection 1.
Historical Context
The protein was identified in the early 1930s during investigations of patients with acute pneumococcal infections 2, 3. Researchers observed that a substance in the serum of these acutely ill patients would precipitate when mixed with the C-polysaccharide component of the pneumococcal cell wall—hence the designation "C-reactive" protein 1.
Evolution of Understanding
Following its initial discovery, CRP was recognized as the prototype acute phase reactant, leading to the broader description of the acute-phase response as a fundamental physiological reaction to tissue injury 1. The protein was subsequently found to increase dramatically in the serum of patients with:
- Bacterial infections
- Rheumatic diseases
- Various inflammatory conditions 2
This established CRP as a nonspecific biomarker of acute inflammation that has been utilized in clinical medicine for decades 4.
Structural and Functional Insights
More recent molecular analysis has revealed that CRP belongs to a unique plasma protein family (including serum amyloid P component) that has been conserved throughout vertebrate evolution 1. The protein demonstrates calcium-dependent binding to phosphocholine and phosphate esters, allowing it to recognize both damaged autologous cells and microbial components 3.
The name "C-reactive protein" thus directly reflects its original discovery as a substance that reacts with the C-polysaccharide of pneumococcal bacteria, a nomenclature that has persisted despite our vastly expanded understanding of its complex biological functions in innate immunity and inflammation 4.