Anti-STAT3 antibodies are used in the immunodetection of the protein signal transducer and activator of transcription 3. In humans, the canonical protein has a reported length of 770 amino acid residues and a mass of 88.1 kDa. Its subcellular localization is in the nucleus and cytoplasm. Up to 3 different isoforms have been reported for this protein. It is notably widely expressed in many tissue types. A member of the Transcription factor STAT protein family, STAT3 is known to be involved with the differentiation of certain cell types. Post-translational modifications have been described, including acetylation and phosphorylation. STAT3 is also used as a cellular marker for characterizing myeloid-derived suppressor cells. Synonyms for this target antigen include ADMIO1, APRF, HIES, DNA-binding protein APRF, acute-phase response factor, and ADMIO. STAT3 gene orthologs have been reported in the mouse, rat, bovine, frog, zebrafish, chimpanzee and chicken species.