The GL-1 monoclonal antibody reacts specifically with the mouse B7-2 (also known as CD86), a costimulatory molecule expressed by B and T lymphocytes, macrophages (thioglycollate-induced from peritoneum), astrocytes and dendritic cells. The memory CD4+ T lymphocytes express CD86 (as mRNA and protein). CD86, and the B7-1 (CD 80) molecule, are ligands for CD152 and CD28, and influence the costimulatory interactions between lymphocytes B and T. B7-2 is also involved in the mouse natural killer cell-mediated cytotoxicity.

The GL-1 antibody blocks the mixed lymphocyte reaction (MLR) and inhibits the T-cells stimulation by antigen-presenting cells. Mixtures of anti-B7-1 antibody and GL-1 were reported to inhibit the interaction between CD125 and its ligand with the in vivo priming of cytotoxic T lymphocytes.