Fecal calprotectin is a polymeric protein which is a marker of inflammation of the gut used as a marker of disease activity in Crohn disease and ulcerative colitis.
Calprotectin is a protein complex from the S-100 family, which is formed of three polypeptide chains, two heavy and one light 3. It was first purified in 1980 and called L1 protein 3.
It is found in especially heavy concentrations in neutrophils and monocytes, and more generally within skin cells, with an organ distribution including the lungs, gastrointestinal tract, oral and cervical mucosae and associated body fluids/secretions.
There are many commercially-available testing kits for calprotectin, many using ELISA (enzyme-linked immunosorbent assay) technology.