CRP, also known as C-reactive protein, is a well-known acute-phase protein conserved throughout evolution. It serves as a host-defense molecule, mediating phagocytosis initiation by labeling damaged cells. This leads to the activation of the classical complement pathway, ultimately eliminating pathogens or damaged cells. CRP is associated with various biological processes such as inflammation and tissue repair, and is an important biomarker in clinical routine, especially for cardiovascular diseases [1,2,3].

CRP levels increase in response to inflammation and infection in humans. In conditions like myocardial infarction, stroke, and COVID-19, CRP can induce damage to potentially regenerable tissue through cell labeling, which is detrimental to cardiac, brain, and lung tissues [1]. In psoriatic arthritis, CRP levels are considered as serum biomarkers, but their inconsistent use in clinical trials limits data generalisability [5]. In Nile tilapia, the CRP gene (On-CRP) promotes inflammation, activates the complement pathway, and improves phagocytic and bacterial agglutination activities during bacterial infection [4].

In conclusion, CRP plays a crucial role in host-defense, inflammation, and tissue repair processes. Its dysregulation is associated with multiple diseases, including cardiovascular diseases, COVID-19, and psoriatic arthritis. Understanding CRP's functions through in vivo studies, as in the case of the Nile tilapia model, helps in clarifying its role in different biological processes and disease conditions.

References:

1. Buerke, Michael, Sheriff, Ahmed, Garlichs, Christoph D. 2022. [CRP apheresis in acute myocardial infarction and COVID-19]. In Medizinische Klinik, Intensivmedizin und Notfallmedizin, 117, 191-199. doi:10.1007/s00063-022-00911-x. https://pubmed.ncbi.nlm.nih.gov/35333926/

2. Agrawal, Alok. 2004. CRP after 2004. In Molecular immunology, 42, 927-30. doi:10.1016/j.molimm.2004.09.028. https://pubmed.ncbi.nlm.nih.gov/15829284/

3. Pathak, Asmita, Agrawal, Alok. 2019. Evolution of C-Reactive Protein. In Frontiers in immunology, 10, 943. doi:10.3389/fimmu.2019.00943. https://pubmed.ncbi.nlm.nih.gov/31114584/

4. Li, Qi, Jiang, Baijian, Zhang, Zhiqiang, Huang, Yu, Jian, Jichang. 2022. CRP Involved in Nile Tilapia (Oreochromis niloticus) against Bacterial Infection. In Biology, 11, . doi:10.3390/biology11081149. https://pubmed.ncbi.nlm.nih.gov/36009776/

5. Houttekiet, Charlotte, de Vlam, Kurt, Neerinckx, Barbara, Lories, Rik. . Systematic review of the use of CRP in clinical trials for psoriatic arthritis: a concern for clinical practice? In RMD open, 8, . doi:10.1136/rmdopen-2021-001756. https://pubmed.ncbi.nlm.nih.gov/35135860/