CD52, also known as Cambridge pathology antigen 1 (CAMPATH-1), is a 25-29 kD glycoprotein containing a large N-linked carbohydrate moiety. The actual molecule of CD52 is only 8-9 kD. It is expressed in the male reproductive tract and on virtually all lymphocytes (T and B cells), as well as macrophages/monocytes, eosinophils, and red cells. CD52 is thought to play a role in carrying and orienting carbohydrates. CD52 is a potent target for complement-mediated lysis and antibody-mediated cellular cytotoxicity and has been used as a depletion target for chronic lymphocytic leukemia (CLL)/lymphoma and immunosuppression. The HI186 antibody is useful for flow cytometry and immunohistochemistry.