This antibody recognizes CD99, an approximately 32 kDa sialoglycoprotein expressed on many cell types, with particularly strong expression on Ewing´s sarcoma and peripheral primitive neuroectodermal tumors. Within the hematopoietic system, CD99 is expressed on virtually all cell types except granulocytes.
CD99 is a ubiquitous transmembrane type I sialoglycoprotein of a unique and poorly characterized protein family. CD99 is heavily O-glycosylated and was described as a T cell costimulator and strong activator of integrin-mediated actin cytoskeleton assembly, promoting cell adhesion and homotypic aggregation, immediate arrest on an inflamed vascular endothelium, and cell migration through it. Ligation of CD99 under some conditions can lead to apoptosis. Originally CD99 was described as a human thymus leukemia antigen, an Ewing´s sarcoma-specific membrane marker, and an adhesion molecule involved in spontaneous rosette formation of T cells with erythrocytes.Synonyms: 12E7, E2 antigen, MIC2X, MIC2Y, Protein MIC2, T-cell surface glycoprotein E2