Anti-I3 antibodies enable researchers to detect and measure the I3 antigen in biological samples. This target is a reported synonym of the BRI3 gene, which encodes brain protein I3. This protein is reported to participate in tumor necrosis factor-alpha (TNF)-induced cell death. The human version of I3 has a canonical amino acid length of 125 residues and a protein mass of 13.6 kilodaltons, although 2 isoforms have been identified. It is reported to be localized in the nucleus, lysosomes and cytoplasm of cells. I3 is a member of the BRI3 protein family.