CD52 / CDW52 is a small glycosylphosphatidylinositol (GPI) anchored glycoprotein. It has a mature peptide comprising only 12 amino acids and is abundantly expressed on human lymphocytes. From the clinical point of view this protein is an important target for therapeutic interventions aimed at leukocyte depletion in hematological malignancies and post-transplant immunosuppression. CD52 / CDW52 may play a role in carrying and orienting carbohydrate. It is an unusually good target for complement-mediated cell lysis.