The HI98 monoclonal antibody specifically reacts with CD15, a 220 kDa carbohydrate moiety also known as SSEA-1, Lewis 3-fucosyl-N-acetyllactosamine (3-FAL). CD15 is expressed on most granulocytes and monocytes to the exclusion of lymphocytes and basophils. It is involved in cell adhesion, chemotaxis, and phagocytosis.