Decrease of lymphoid dendritic cells in blood from malaria-infected pregnant women.

Activation of dendritic cells (DCs) during malaria is poorly documented and has mainly been studied in rodent models. We conducted studies in Senegal to better understand the relationship between DC subset activation and susceptibility of pregnant women to malaria. For each woman, samples were collected at delivery from peripheral (WB), placental (PB) and cord blood (CB). The ex vivo phenotypes of DCs were assessed using flow cytometry on whole blood. The percentage of total DCs was the same for malaria-infected or non-infected pregnant women, except for PB where a decrease in DCs was observed during infection. Lymphoid dendritic cells (LDC) also decreased in the three blood compartments of infected pregnant women and less differentiated DCs (ldDCs) increased. During infection, Human Leucocyte Antigen DR (HLA-DR) expression decreased on LDCs, myeloid DCs (MDCs) and ldDCs. IL-10 increased in the three blood compartments. These data demonstrate a modulation of DC sub-populations during placental malaria. A decrease in LDCs during placental malaria could trigger major alterations in the immune response and a change in the Th1/Th2 balance. However, elevated IL-10 observed during infection substantiates a normal micro-environment triggering normal production of DCs. The decrease in LDCs could thus be due to their migration towards spleen or other lymphoid organs.