The Frequency of Peripheral Blood CD4+ CD25high FoxP3+ and CD4+ CD25- FoxP3+ Regulatory T Cells in Normal Pregnancy and Pre-Eclampsia

Problem: Regulatory T cells (Tregs) play an important role in the development of pregnancy-specific immune tolerance. We aimed to determine the peripheral frequency of a recently described Treg subpopulation, the CD4+ CD25- FoxP3+ Treg subset, and its correlation with the conventional CD4+ CD25high FoxP3+ Tregs in normal pregnancy (NP) and pre-eclampsia (PE) compared to non-pregnant (non-P) women. We also examined the proportion of the activated CD4+ CD25high FoxP3high Treg subset within conventional Treg cells. Method: We took peripheral blood samples from 20 PE, 20 NP, and 12 non-P women and determined the frequency of the above Treg subsets using flow cytometry. Results: The frequency of conventional CD4+ CD25high FoxP3+ Tregs and activated CD4+ CD25high FoxP3high Tregs, but also that of non-conventional CD4+ CD25- FoxP3+ Tregs was higher in NP compared to non-P women, but lower again in PE, reaching comparable levels to the non-P group. The ratios of CD4+ CD25high FoxP3+ and CD4+ CD25- FoxP3+ Treg subsets were constant in all three investigated groups. Conclusion: Our results indicate that the frequency of conventional and non-conventional Tregs alters simultaneously, and the presence in circulation of both of these Treg subsets is similarly important in the adequate development of pregnancy-specific immune tolerance.