C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin-6 secretion by macrophages and T cells. Its physiological role 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 C1q. CRP is synthesized by the liver in response to factors released by macrophages and fat cells (adipocytes). C-reactive protein was the first pattern recognition receptor (PRR) to be identified. CRP is used mainly as a general marker for inflammation and infection. Apart from liver failure, there are few known factors that interfere with CRP production. CRP can be used as a very rough proxy for heart disease risk. Measuring and charting CRP values can prove useful in determining disease progress or the effectiveness of treatments.