Suppressed peripheral and placental blood lymphoproliferative responses in first pregnancies: relevance to malaria.

An understanding of processes that predispose pregnant women, and in particular primigravidae, to malaria infection is essential to improve malaria management in pregnancy. Lymphoproliferative responses to malaria-specific (F32, 190L, and 190N) as well as other antigens (Candida and purified protein derivative [PPD]) were examined in the peripheral and placental blood of 102 Gambian women at the time of delivery. The lymphoproliferative responses of placental cells were poor to all antigens compared with those of peripheral blood (Candida P < 0.001, PPD P < 0.001, F32 P = 0.008, 190L P = 0.003, and 190N P = 0.10). Reduced proliferative capacity of placental mononuclear cells may contribute to heavy parasite colonization of this organ. Proliferation to malarial and PPD but not Candida antigens was selectively suppressed in peripheral and placental blood of primiparae relative to multiparae (F32 P = 0.07, 190L P = 0.09, 190N P = 0.007, PPD P = 0.09). Autologous plasma contained factors that suppressed lymphoproliferative responses to the same series of antigens to which the primiparae responded poorly (F32 P < 0.001, 190L P < 0.001, 190N P < 0.001, PPD P = 0.03). Malarial antibody levels were comparable among women of different parities and between peripheral and placental blood. Primigravidae may be more susceptible to malaria because of unique physiologic factors, such as higher levels of circulating immunosuppressive corticosteroids (P < 0.001), rather than differences in levels of acquired immunity.