Alkaline phosphatase (ALP) is a cell surface enzyme that catalyzes the conversion of an orthophosphoric monoester and water to an alcohol and orthophosphate. Most mammals exhibit four isozymes of ALP with selective expression in distinct tissues; placenta, placenta-like, intestine, and tissue non-specific (1). The liver/bone/kidney isozyme, also called tissue non-specific alkaline phosphatase, was originally cloned from an osteosarcoma cell line screened with anti-liver ALP antiserum (2). Antibodies to ALP have been used in lineage studies to characterize the development of osteoclasts and adipocytes (3, 4). In addition to its expression on the cell surface, neutrophil alkaline phosphatase is found within the secretory granules of neutrophils and is released into the serum (5). Hypophosphatasia, a genetic metabolic disorder resulting from a deficiency in serum and bone alkaline phosphatase activity, manifests itself in patients with severe skeletal defects (6, 7). Neutrophil alkaline phosphatase is often used diagnostically in various pathologies including myeloid cancers (5, 8), Down