CD317 (Cluster of differentiation 317), also referred to BST-2, TETHERIN or bone marrow stromal cell antigen 2, is a type II transmembrane protein whose N-terminus is in the cytoplasm and lumen C-terminus is modified by a glycosylphosphatidylinositol (GPI) anchor. The unique topological structure of CD317 enables its interaction with the cell or virus lipid bilayer at each of its ends. It is a new component of the innate immune system responding to enveloped viruses. CD317 can inhibit members of the retrovirus, arenavirus, filovirus, and herpesvirus families, which code for various proteins to degrade CD317 and/or keep it away from its acting site. It is reported to express on the plasma membrane and within certain endosomal membrane compartments, including the trans-Golgi network (TGN) and the early or recycling endosome. FcγRIII, synonymously also referred to CD16, is a type III Fcγ receptor which has other two identified members: a high-affinity receptor FcγRI (CD64) and a low-affinity one FcγRII (CD32). This transmembrane protein, FcγRIII, contains two extracellular immunoglobulin (Ig)-like domains with low-affinity for IgG. It is responsible for antibody-dependent cellular cytotoxicity. FcγRIII is expressed on large granular lymphocytes of both nature killer (NK)- and T-cell types. There are two different isoforms of it in humans named FcγRIIIa and FcγRIIIb, sharing 96% sequence identity in extracellular Ig binding regions. FcγRIIIa is a transmembrane receptor found on macrophages, mast and NK cells. FcγRIIIb is expressed exclusively on neutrophils and functions as the only Fc receptor anchored via a glycosyl-phosphatidylinositol (GPI) linker to the cell membrane.