Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disorder that affects women at childbearing age. During pregnancy, maternal immune system is challenged to tolerate a semi-allogenic fetus and a shift toward a tolerogenic profile is essential. Failure to develop this tolerogenic profile seems to be associated with the development of adverse obstetric outcomes. We conducted a prospective longitudinal observational study where peripheral blood lymphocyte subsets were analyzed during pregnancy in a group of SLE patients and compared with healthy gestations. We observed a reduction in peripheric Treg cell count throughout all pregnancy in control patients, which was not observed in SLE patients. In contrast, the Th17 cell count remained stable in both groups. In the control group, the Treg/Th17 ratio decreased throughout pregnancy to the postpartum, which was not observed in the study group. These changes may be justified by the migration of the immunotolerant Treg cells to the maternal decidua and may lead to the establishment of a pro-inflammatory profile by the end of pregnancy in healthy pregnancies, which was not observed in the SLE pregnant patients. This pro-inflammatory state at the end of a healthy pregnancy may be necessary for the spontaneous beginning of labor and help to explain why systemic syndromes like preeclampsia develop during the second half of pregnancy. The lack of these findings in SLE patients may express a pro-inflammatory state from the beginning of pregnancy, the influence of immunomodulatory medication or an intrinsic deregulation of immune function, which is a characteristic of these patients.
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