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

Problem The function of IL-10 producing regulatory B cells (Breg) during gestation is unknown. Here, we aimed to understand their participation in early pregnancy. Method CD19+ CD24hi CD27+B cell frequency, measured by flow cytometry, increased with pregnancy onset but not in the case of spontaneous abortions. Results B 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. Conclusions Breg emerge as important players in pregnancy; they suppress undesired immune responses from maternal T cells and are therefore important for tolerance acquisition. [ABSTRACT FROM AUTHOR]