Altered dendritic cell function in normal pregnancy

In pregnancy, maternal immunity is skewed to favour maintenance of gestation and immune tolerance of a semi-allogeneic fetus. Dendritic cells are thought to play a crucial role in mediating the balance between immunity and tolerance, and determining the type of T helper cell response. We postulated that myeloid dendritic cells would be modified in pregnancy to favour type 2 T helper cell responses. We show that the proportion of circulating myeloid dendritic cells expressing CD86 and staining for HLA-DR were significantly lower in the third trimester of pregnancy compared with non-pregnant women. As pregnancy progressed through the third trimester to term, CD86 expression increased. Furthermore, monocytes from pregnant women differentiated into less phenotypically mature dendritic cells which expressed lower levels of CD80, CD86 and HLA-DR molecules compared with non-pregnant women. In response to inflammatory stimuli, monocyte-derived dendritic cells, from pregnant women up-regulated CD86 more than CD80, and secreted less IL-12p70 but more IL-10, compared with monocyte-derived dendritic cells from non-pregnant controls. Our results demonstrate that, in pregnancy, the dendritic cell system is modified to favour type 2 T helper cell responses.