• Human pregnancy;
  • nonspecific immunosuppressive factors

ABSTRACT: Recent evidence has demonstrated that the non-specific immunosuppression that develops during pregnancy is not due to the de novo synthesis of immunosuppressive factors (ISF) but is a result of the activation of pre-existing molecules. The latter are present in normal sera as inactive complexes with a molecule which is specifically depleted following conception resulting in the activation of the ISF; the depleted molecule is termed the pregnancy-depleted immunoregulatory factor (pdIRF). Since non-specific ISF are detected in various diseases, it is proposed that the ISF-pdIRF relationship observed in pregnancy is a universal phenomenon and that the depletion of pdIRF and the activation of ISF can be achieved by a variety of stimuli. It is further proposed that abortion-prone women fail to adequately deplete their pdIRF levels so that the ISF are not activated. However, owing to the universal nature of the system, lymphocyte transfusion therapy supplies the necessary stimuli so that the pdIRF levels are depleted and the ISF activated which ensures a successful outcome to the pregnancy.