The J116 monoclonal antibody reacts with the human CD279, also known as programmed death-1 (PD-1),a 55 kDa glycoprotein belonging to the CD28 family of the Ig superfamily.PD-1 is expressed predominantly on activated T and B lymphocytes cells and thymocytes,  It is induced  on activated myeloid cells. PD-1 involved in lymphocyte clonal selection and peripheral tolerance through binding its ligands, B7-H1 (PD-L1) and B7-DC (PD-L2). It has been reported that PD-1 and PD-L1 interactions are critical to positive selection and play a role in shaping the T cell repertoire. Evidence reported to date suggests overlapping functions for these two PD-1 ligands and their constitutive expression on some normal tissues and upregulation on activated antigen-presenting cells. Binding of the J116 monoclonal antibody inhibits PD-1 signal transduction, however, it does not block binding of the ligand PD-L1.