The protein CD86 (Cluster of Differentiation 86) is a molecule expressed on antigen-presenting cells that provide costimulatory signals necessary for T cell activation and survival. It is the ligand for two proteins at the cell surface of T cells, CD28 antigen and CTLA-4 (cytotoxic T-lymphocyte-associated protein 4). CD86 is also known as B7.2. Its principal mode of action is by binding to CD28. Along with CD80, these molecules provide the necessary stimuli to prime T cells against antigens presented by antigen-presenting cells. This gene encodes a type I membrane protein that is a member of the immunoglobulin superfamily. Binding of this protein with CD28 antigen is a costimulatory signal for activation of the T-cell. Binding of this protein with CTLA-4 negatively regulates T-cell activation and diminishes the immune response.