CD57 recognizes a (Mr 100-110kDa) oligosaccharide antigenic determinant on myeloid cells and on a variety of polypeptides，lipids and chondroitan sulfate proteoglycans. This surface antigen is associated with myelin-associated glycoprotein (MAG). The CD57 antigen is present on 15-20% of normal peripheral blood mononuclear cells. It is expressed on a subset of natural killer cells (60%) and on a subset of T-lymphocytes. This carbohydrate is also present on N-CAM in the nervous system.