Mechanisms underlying immunologic states during pregnancy: Possible association of the sympathetic nervous system

NH and extrathymic T cells are abundant in the decidua of the pregnant uter us, To determine how this unique pattern is induced, overall populations of leukocytes were examined in the blood and other tissues in pregnant women. Time-kinetic studies showed that a basal change of leukocytes during pregn ancy was granulocytosis and lymphocytopenia in the blood. This change might be due to sympathetic nerve activation during pregnancy, because the admin istration of catecholamine is known to activate myelopoiesis in the bone ma rrow. In addition to the numerical change, the functional activation of NK and extrathymic T cells also seemed to be present. This might be due to NH cells and extrathymic T cells (as well as granulocytes), which carry a high density of surface adrenergic receptors. Such functional activation of NK and extrathymic T cells was more prominent in the blood and urine in patien ts with preeclampsia and hyperemesis gravidarum than in normal pregnant wom en. The present results suggest that the activation of granulocytes, NK cel ls, and extrathymic T cells is essential for the maintenance of pregnancy b ut that overactivation thereof may be responsible for the onset of pregnanc y disorders. (C) 1999 Academic Press.