CD2, also known as LFA-2, is a member of the immunoglobulin gene family with an approximate molecular weight of 45 kD. It is expressed on thymocytes, peripheral T cells, dendritic epidermal T cells, macrophages in the spleen, and NK cells. CD2 can associate with the T cell receptor and participate in T cell activation through adhesion and signal transduction. CD2 binds to CD48, CD58, and CD59. The OX-34 antibody blocks CD48 binding to CD2. It has been reported to partially block T cell activation and inhibit the mixed lymphocyte reaction in vitro. The OX-34 antibody has also been used to deplete peripheral T cells and prevent allograft rejection in vivo.