CD69 is a disulfide linked transmembrane homodimer whose differentially glycosylated subunits range from 35-39 kDa. It is a C type lectin, most closely related to the NKRP1 and Ly49 NK cell activation molecules. CD69 is involved in lymphocyte proliferation and functions as a signal transmitting receptor in lymphocytes, natural killer (NK) cells, and platelets. It is the earliest inducible cell surface glycoprotein acquired during lymphoid activation. Induction occurs by antigens, mitogens or activators of PKC on the surface of T and B lymphocytes, and by interaction of IL2 with the p75 IL2R on the surface of NK cells. Constitutive expression of CD69 on subsets of thymocytes suggests that it may be involved in regulation of developmental events in addition to its role in activation of a variety of hematopoietic cells.
