CD86 (also known as B7.2) is a costimulatory molecule belonging to the immunoglobulin superfamily. Primarily expressed on antigen-presenting cells (APCs)，including B cells，dendritic cells，and macrophages，CD86 is the ligand for two proteins at the cell surface of T cells，CD28 antigen and cytotoxic T-lymphocyte-associated protein 4. Binding of CD86 with CD28 antigen is a costimulatory signal for activation of the T-cell. Binding of CD86 with cytotoxic T-lymphocyte-associated protein 4 negatively regulates T-cell activation and diminishes the immune response.