CD66b is a 95-100 kD glycosylphosphatidylinositol (GPI)-linked protein also known as CD67, CGM6, and NCA-95. CD66b is a member of the immunoglobulin superfamily, carcinoembryonic antigen (CEA)-like subfamily. CD66b, expressed on granulocytes, has been reported to induce activation in neutrophils and to be involved in heterophilic adhesion with CD66c.