C-reactive protein (CRP) is an acute-phase protein; it serves as a marker of inflammation. It derives its name from its ability to precipitate the C-polysaccharide of Streptococcus pneumonia. Synthesis of CRP occurs in the liver and is triggered by the release of cytokine interleukin IL-6 in response to tissue damage or infectious stimuli. CRP functions by opsonizing bacteria, marking them for destruction by the complement cascade. CRP is released early in infection (the first 4–24 hours) during the same window that many other components of inflammation are being activated, such as inflammatory cytokines.IL-6 induces production of CRP as part of the initial immune response against an invading pathogen that triggers the rest of the immune response. However, because it is far easier to measure than cytokines or other proteins, high levels of CRP are a more consistent marker of a recent infection or heavy immunological involvement, as is the case in several autoimmune diseases. In burns, elevation of serum CRP is well documented.CRP has been proposed as an early predictor of sepsis in burned children.

CRP is a highly stable analyte in serum or plasma, which can be measured easily and reproducibly. CRP level is a non-specific measure of inflammation that may be useful for screening and monitoring response to treatment. CRP has also emerged as an independent risk factor for adverse outcomes in diverse clinical settings. None of the other upstream mediators or downstream effectors of inflammation including other acute-phase reactants have such desirable characteristics; rendering CRP the most commonly used measure of inflammation.