Current theories of pre-eclampsia (PE) pathogenesis involve multiple pathways leading to abnormal placentation, failed angiogenesis, poor oxygenation, pro-inflammatory responses and complex immunological processes. Dendritic cells (DC) are rare but potent antigen-presenting cells that may alter the placental immunological microenvironment. DC have been implicated as key regulators in pregnancy maintenance through their tolerance-promoting functions. Loss of DC-mediated tolerance may be involved in PE pathogenesis. Myeloid DC have been identified in decidua and are recruited into pre-eclamptic decidua, which expresses many monocytes and DC chemotactic and differentiating cytokines. The role of plasmacytoid DC in pregnancy and PE is unknown.
Aims:To identify DC subsets within human placenta, and establish methods for enumeration and comprehensive phenotyping of DC subsets from placental samples.
Methods:Samples of decidual tissue taken at elective caesarean section were non-enzymatically dissociated, and DC identified within a density gradient separated mononuclear population by 4-6 colour flow cytometry cell surface marker analysis, using a panel of DC-specific anti-human antibodies. The gating strategy first identified the lineage (CD14,CD20,CD3,CD56) negative, HLA-DR+ population.Myeloid DC were identified within this population as CD1c (BDCA-1)+ or CD141+.Plasmacytoid DC were BDCA-2+.
Results:We studied nine placenta for DC analysis, seven of which had results suitable for analysis.CD1c+ Myeloid DC comprised 0.116-0.265% of the cells identified.A much rarer subset of CD141+ myeloid DC were also identified (0.017-0.059 %).Plasmacytoid DC comprised 0.014-0.269% of the total population using BDCA-2 as a PDC marker.A DC-SIGN+ population was also noted (0.043-0.068 %).
Conclusions:We have established a reliable method for enumerating and phenotyping DC subsets in the placenta and established the presence of a population of plasmacytoid DC in human decidua in late pregnancy.This is preliminary data from an ongoing study in which we will compare DC phenotype, number and function from peripheral blood as well as placental samples, in women with PE versus normal pregnancy.