Calprotectin, also known as MRP-8/MRP-14 or S100A8/A9 heterocomplex, is formed out of the calcium-binding, migration inhibitory factor-related proteins, MRP-8 (S100A8) and MRP-14 (S100A9). The expression of these proteins is largely confined to the cytosol of neutrophils and monocytes. The complex formation of these proteins is calcium-dependent. Calprotectin comprises 60% of the cytoplasmic protein fraction of circulating polymorphonuclear granulocytes and is also found in monocytes, macrophages and ileal tissue eosinophils. Peripheral blood monocytes carry the antigen extra- and intracellularly, neutrophils only intracellularly. Calprotectin has antibacterial, antifungal, immunomodulating and antiproliferative effects. Furthermore, it is a potent chemotactic factor for neutrophils. Plasma concentrations are elevated in diseases associated with increased neutrophil activity. During intestinal wall inflammation, granulocytes transmigrate through the intestinal wall. Therefore Calprotectin is also detectable in faeces. Several investigations report that faecal Calprotectin is significantly increased in intestinal diseases such as inflammatory bowel disease (IBD), Crohn´s disease, ulcerative colitis and colon cancer.
Normal human plasma contains a Calprotectin concentration ranging from ~100 to 3000 ng/ml.
The human Calprotectin ELISA kit is to be used for the in vitro quantitative determination of human Calprotectin in plasma, serum and feces samples.
The human Calprotectin ELISA is a ready-to-use solid-phase enzyme-linked immunosorbent assay based on the sandwich principle with a working time of 3½ hours. The efficient format of a plate with twelve disposable 8-well strips allows free choice of batch size for the assay. Samples and standards are incubated in micro titer wells coated with antibodies recognizing human Calprotectin. Biotinylated tracer antibody will bind to captured human Calprotectin. Streptavidin-peroxidase conjugate will bind to the biotinylated tracer antibody. Streptavidin-peroxidase conjugate will react with the substrate, tetramethylbenzidine (TMB). The enzyme reaction is stopped by the addition of oxalic acid. The absorbance at 450 nm is measured with a spectrophotometer. A standard curve is obtained by plotting the absorbance (linear) versus the corresponding concentrations of the human Calprotectin standards (log). The human Calprotectin concentration of samples, which are run concurrently with the standards, can be determined from the standard curve.