Cutting Edge: IL-10-Producing Regulatory B Cells in Early Human Pregnancy

ProblemThe function of IL-10 producing regulatory B cells (Breg) during gestation is unknown. Here, we aimed to understand their participation in early pregnancy. MethodCD19(+)CD24(hi)CD27(+)B cell frequency, measured by flow cytometry, increased with pregnancy onset but not in the case of spontaneous abortions. ResultsB cells from non-pregnant women cultured with serum from normal pregnant women produced higher IL-10 levels than those cultured with serum from spontaneous abortion patients or autologous serum. CD19(+)-activated B cells from pregnant women strongly suppressed TNF-a production by CD4(+)T cells when cocultured. We identified hCG as an important factor regulating the number and function of Breg during pregnancy. ConclusionsBreg emerge as important players in pregnancy; they suppress undesired immune responses from maternal T cells and are therefore important for tolerance acquisition.