CD52 antigen--a review.

Human CD52 is a glycosylphosphatidylinositol (GPI)--anchored antigen expressed on the all lymphocytes as well as within the male genital tract, where it can be produced by epithelial cells of the distal epididymis and duct deferens. CD52 can be shed into seminal plasma and then acquired by sperm cells during their passage through the genital tract, thus it is detectable on the surface of epididymal sperm and in the ejaculate but not on either spermatogenetic cells or testicular spermatozoa. Protein core of the sperm and lymphocyte CD52 is identical and it is a product of a single copy gene located on chromosome 1. However, N-linked carbohydrate side chains (attached to Asn-3) and GPI-anchor structure are different. Physiological role of CD52 on lymphocytes is unclear, although antibody directed to CD52, CAMPATH-1, is capable of complement activation and it can be clinically useful to treat lympho-proliferative disorders and to deplete lymphocytes in bone marrow transplants. Monoclonal antibodies directed against sperm CD52 may cause sperm immobilisation and agglutination and affect hamster oocyte penetration suggesting an association of this molecule with fertilisation.