Anti-S1R antibodies are used in antigen-specific immunodetection in biological samples. The target S1R is a known alias name of the protein transmembrane BAX inhibitor motif containing 4, encoded by the TMBIM4 gene in humans. This 238-amino acid residue protein is reported to be an anti-apoptotic protein, which can inhibit apoptosis induced by intrinsic and extrinsic apoptotic stimuli. It is localized to the Golgi of the cell. Other synonyms for S1R include CGI-119, GAAP, and LFG4.