C-reactive protein (CRP) is an annular, pentameric protein. The physiological role of CRP is to bind to lysophosphatidylcholine expressed on the surface of dead or dying cells (and some types of bacteria) in order to activate the complement system via the C1Q complex. CRP is an acute phase protein in humans and is an important mediator of immune host defense. The acute phase response occurs in response to a wide range of acute and chronic inflammatory conditions such as bacterial, viral, or fungal infections; rheumatic and other inflammatory diseases; malignancy; and tissue injury and necrosis. These conditions cause release of IL-6 and other cytokines that trigger the synthesis of CRP and fibrinogen by the liver. CRP plays a role in innate immunity as an early defense system against infections.
Monitoring of CRP levels in serum provides more detailed insights in several pathological situations such as inflammatory disease (including inflammatory bowel disease, Intestinal Lymphoma, Intestinal Tuberculosis and Behcet’s Syndrome), cancer, diabetes, hypertension, cardiovascular disease, obstructive sleep apnea and so on.