Recognizes a protein of14kDa, identified as MRP-14 (also known as Calgranulin B or S100AA9). It 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. It is a potent chemotactic factor for neutrophils. Plasma concentrations are elevated in diseases associated with increased neutrophil activity, like inflammatory bowel disease. Granulocytes terminate their existence after transmigration through the intestinal wall. Therefore, it is also detectable in feces. Elevated levels have been observed in body fluids such as plasma, saliva, gingival crevicular fluid, stools, and synovial fluid during infection and inflammatory conditions. This MAb reacts with neutrophils, monocytes, and macrophages, and has been shown as an important marker for identifying macrophages in tissue sections.