Abstract Introduction: Pregnancy-specific glycoprotein 9 (PSG9) is one of 10 members of a conserved glycoprotein family within the carcinoembryonic antigen superfamily expressed by placental trophoblasts and secreted into maternal circulation. PSG1 and PSG9 induce the conversion of naïve T cells into regulatory T cells by increasing active transforming growth factor-beta (TGF-β) availability and were predicted to share anti-inflammatory activity in innate immune cells.
