CRP is produced in hepatocytes, mainly under the transcriptional control of cytokines, IL-6 and IL-1. CRP is a major acute-phase reactant and the most important marker for the diagnosis of systemic inflammation in clinical practice. During an acute immune response, levels can increase more than 1000-fold and peak after about 48 h. Low levels of the so-called high-sensitivity (hs- ) CRP below 10 μg/mL are typically found in the general population.
Serum amyloid A (SAA) is another key acute-phase protein and is coded by four different genes. SAA production occurs in the liver and is driven by IL- 6, IL-1, and TNF-α. During acute inflammation, SAA is secreted into the circulation where concentrations could increase more than 1000-fold compared to normal values of <5 μg/mL. 
Calprotectin is a heterocomplex of S100A8 and S100A9, and belongs to endogenous danger-associated molecular patterns (DAMPs) which are intracellular molecules that amplify an immune response and promote inflammation by interaction with Toll-like receptors (TLRs) and receptors for advanced glycation end products (RAGE). Elevated blood levels have been associated with various inflammatory diseases, such as rheumatoid arthritis, atherosclerosis, CVD, metabolic syndrome, and different types of cancer.