title: Pregnancy-associated nonspecific immunosuppression: mechanism for the activation of the immunosuppressive factors.
abstract: The nonspecific immunosuppressive effect observed in pregnancy sera and mediated by two factors, immunosuppressive factors (ISF) I and II, was regulated by a third molecule termed the pregnancy-depleted immunoregulatory factor (pdIRF). Natural depletion of serum pdIRF levels during pregnancy resulted in the activation of the ISF-I and ISF-II molecules, which prior to conception existed in the serum in inactive forms. The inactive ISF-I and ISF-II molecules in male sera and in nulliparous nonpregnant female sera can be activated following the artificial selective depletion of pdIRF by absorption onto Sephacryl S-300. It is proposed that inactive complexes consisting of the ISF-I and ISF-II molecules and pdIRF and possibly involving Ca2+ and Mg2+ ions are a feature of normal sera. The pdIRF molecule has an apparent Mr of 100,000-125,000 daltons and consists of a single major polypeptide of 63,000 daltons. Equal concentrations of pdIRF are present in male and female normal sera.
mesh_terms: D002118:Calcium / Q000097:blood; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007165:Immunosuppression Therapy; D008274:Magnesium / Q000097:blood; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third
chemical_list: D007074:Immunoglobulin G; D008274:Magnesium; D002118:Calcium