Polymorphonuclear leukocytes in the fetal membranes are activated in patients with preterm delivery: ultrastructural and enzyme-histochemical evidence.

The purpose of this study was to examine evidence for the presence of activated leukocytes in the fetal membranes from patients with preterm delivery. Polymorphonuclear leukocytes in fetal membranes from seven patients with preterm delivery (26-32 weeks of gestation) were analysed using transmission electron microscopy and ultrastructural enzyme-histochemistry for peroxidase and alkaline phosphatase. A large number of leukocytes accumulated in the fetal membranes from preterm deliveries. Phagosome, phagocytosis of cell debris, attachment of primary granules to the phagosomal membrane and cell surface projections were observed in fetal membrane leukocytes from preterm delivery but not in peripheral blood leukocytes. Peroxidase and alkaline phosphatase activity was demonstrated on the plasma membrane of the phagosomes. Morphological and enzyme-histochemical observation indicated that polymorphonuclear leukocytes in the fetal membrane in patients with preterm delivery were stimulated or activated. Such activated leukocytes may play a role in the pathophysiology or pathogenesis of preterm delivery.