Specificity: Reacts with CD50 (ICAM-3), a 120-130 kD type I membrane protein (immunoglobulin supergene family) expressed on leukocytes, endothelial cells and Langerhans cells; it is negative on platelets and erythrocytes. The MEM-04 blocks DC-SIGN (CD209) binding to ICAM-3 (epitope in D1).