It recognizes a 220kDa carbohydrate structure which is identified as 3-fucosyl-N-acetyllactosamine (3- FAL) and is also known as CD15 or X-hapten. CD15 plays a role in mediating phagocytosis, bactericidal activity, and chemotaxis. It is present on >95% of granulocytes including neutrophils and eosinophils and to a lesser degree on monocytes. In addition, CD15 is expressed in Reed-Sternberg cells and some epithelial cells. CD15 antibody is very useful in the identification of Hodgkin's disease. CD15 is occasionally expressed in large cell lymphomas of both B and T phenotypes which otherwise have a quite distinct histological appearance.