Migration inhibitory factor-related proteins MRP8 (S100A8) and MRP14 (S100A9) are members of the S100 family of calcium binding proteins. They are highly expressed in resting neutrophils, keratinocytes, infiltrating tissue macrophages, and on epithelial cells in active inflammatory disease. Human MRP8 has a molecular weight of 11.0 kD, while human MRP14 exists in a 13.3 kD and a truncated 12.9 kD form. Calcium induces the formation of MRP8/14 heterocomplexes (calprotectin). MRP8/14 complexes are produced in large quantity by activated granulocytes and monocytes.MRP8, MRP14, and their heterodimer MRP8/14 have been shown to have major roles in inflammatory and immunological responses. MRP8 and MRP14 regulate myeloid cell function by binding to Toll-like receptor-4 and the receptor for advanced glycation end-products (AGE). One major function of the MRP8/14 heterocomplex is its antimicrobial activity (hence the name calprotectin) by inhibiting the growth of pathogens through competition for zinc. MRP8/14 also regulates vascular inflammation and contributes to the biological response to vascular injury by promoting leukocyte recruitment, macrophage cytokine production, and SMC proliferation. In addition, MRP8/14 heterocomplex has a unique role as a fatty acid transport protein. This makes MRP8/14 an important mediator between calcium signaling and arachidonic acid effects.MRP8/14 proteins are regarded as markers for a number of inflammatory diseases in humans. Various conditions have shown significant correlation of MRP8/14 levels with disease activity. For example, MRP8/14 levels in stool are a reliable indicator of intestinal inflammatory conditions and can be used to predict relapse in inflammatory bowel diseases. Plasma MRP8/14 level can be a marker for acute rejection in kidney allograft transplantation. Concentrations of MRP8/14 in serum, and particularly in synovial fluid, correlate strongly with disease activity in rheumatoid arthritis. In Systemic Lupus Erythematosus (SLE) patients, serum levels of MRP8/14 are higher than in healthy controls and are associated with disease activity. MRP8/14 may also be a useful biomarker of platelet and inflammatory disease activity in atherothrombosis. Increasing plasma concentrations of MRP-8/14 among healthy individuals can predict the risk of future cardiovascular events. BioLegend’s LEGEND MAX(TM) Human MRP8/14 (Calprotectin) ELISA Kit is a Sandwich Enzyme-Linked Immunosorbent Assay (ELISA) with a 96-well strip plate that is pre-coated with a capture antibody. This kit is specifically designed for the accurate protein quantitation of human MRP8/14 from cell culture supernatant, serum, plasma, and other biological fluids. It is analytically validated with ready-to-use reagents.