The FCR-4G8 monoclonal antibody reacts with mouse CD16⁄CD32 (FcγIII⁄II receptors) which are Fc receptors present on macrophages, NK cells, monocytes, lymphocytes, and dendritic cells. The FCR-4G8 monoclonal antibody can be used to block Fc receptor mediated binding of immunoglobins to the FcγIII and FcγII receptors.