The proposed research is designed to explore the relationships between infections and pregnancy. In particular, three host-defense mechanisms, phagocytosis, cell-mediated immunity and humoral immunity will be examined. This will be accomplished by comparative studies of these three host defense mechanisms in non-pregnant women, pregnant women with and without complications, and in women taking oral contraceptives. Continuation of our studies in phagocytosis will seek to define (1) the enzymatic basis of increased phagocytosis-associated leukocytic metabolism in pregnancy, (2) the mechanism of estriol stimulation of myeloperoxidase-dependent leukocytic bactericidal activity in pregnancy, and (3) the relationship of estriol levels and anemia to abnormal leukocytic functions in pregnancy complicated with infections. In addition, this aspect of our study will be expanded to include characterization of phagocytosis-associated leukocytic activity in women taking oral contraceptives. We also plan to extend these studies to include evaluation of other host defense mechanisms, i.e. cell-mediated immunity and humoral immunity. When necessary animal models will be used for evaluation of the relationship of a particular alteration in host defense to susceptibility to infection and to further characterize mechanisms altering host defense.