CD52 is a small glycoprotein expressed on various immune cells, including T cells, B cells, some myeloid cells, and sperm. It has a simple structure, mainly consisting of a short peptide chain and a long glycosylated portion, lacking transmembrane and intracellular regions. CD52 is located on the cell surface, and although its specific biological function is not fully understood, it may play a role in regulating immune responses and intercellular signaling. Its specific expression pattern makes CD52 a target for certain immune-mediated diseases and cancer therapies. Currently, antibody drugs targeting CD52 have been developed for the treatment of chronic lymphocytic leukemia and multiple sclerosis, and its abnormal or altered expression may affect disease progression and treatment response.