BTN3A1, also named as Butyrophilin subfamily 3 member A1 or BTF5, is a 513 amino acid protein ,which contains one B30.2/SPRY domain and two Ig-like V-type (immunoglobulin-like) domains. BTN3A1 localizes in the cell membrane and belongs to the immunoglobulin superfamily. BTN/MOG family. BTN3A1 is detected on T-cells, natural killer cells, dendritic cells and macrophages. It is ubiquitously highly expressed in heart, pancreas and lung and moderately expressed in placenta, liver and muscle. BTN3A1 plays a role in T-cell activation and in the adaptive immune response. It also regulates the proliferation of activated T-cells and the release of cytokines and IFNG by activated T-cells. It exists as four isoforms. We detected a 48 kda isoform by western blot.