Immunoglobulin superfamily member 8 is a protein that in humans is encoded by the IGSF8 gene. IGSF8 has also been designated as CD316. Acts as an inducible receptor of HSPA8 on dendritic cells to enhance the CCL21/SLC-dependent migration of activated mature dendritic cells while attenuating their antigen-specific stimulatory capacities. In complex with alpha-actinins ACTN1 and ACTN4, regulates actin dynamics in the immune synapse and subsequent T-cell activation. Inhibits the entry of several viruses such as hepatitis C Virus (HCV) or HIV-1. Mechanistically, promotes a change in CD81 organization at the plasma membrane by significantly restricting its diffusion which in turn influences CD81 interaction with Claudin-1/CLDN1, preventing CLDN1 from acting as a co-receptor required for HCV entry. Accumulates at the presynaptic terminal, the producer cell side of the virological synapse, to prevent HIV-1 Env-mediated cell-cell fusion. Highly expressed on malignant cells with antigen presentation defects, interacts with NK receptor KIR3DL2 to suppress NK-cell cytotoxicity.