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(+) CD24(hi) 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.