Lower activation of CD4⁺ memory T cells in preeclampsia compared to healthy pregnancies persists postpartum

Insufficient adaptations of the maternal immune system are associated with pregnancy complications such as preeclampsia. Memory T cells might be implicated in the pathophysiology of preeclampsia and its recurrence risk. Therefore, peripheral blood samples were taken from healthy pregnant women (n = 15), preeclamptic pregnant women (n = 15), formerly healthy pregnant women (n = 16), and formerly preeclamptic women (n = 15). CD4⁺ and CD8⁺ memory cells (CD45RO⁺), central-memory cells (CM, CD45RO⁺CCR7⁺), effector-memory cells (EM, CD45RO⁺CCR7^-), and their activated (CD69⁺) proportions were analyzed using flow cytometry. A magnetic Luminex assay was performed on plasma samples from all groups to analyze 16 cytokines associated with memory T cells homeostasis and T cell differentiation. Proportions of CD4⁺ and CD8⁺ memory cell populations did not differ between preeclamptic and healthy pregnant women or between formerly preeclamptic and formerly healthy pregnant women. However, activated proportions of the general CD4⁺ memory, CD4⁺ EM, and CD4⁺ CM population in the peripheral blood were lower during preeclampsia compared to healthy pregnancies and were also lower postpartum in formerly preeclamptic compared to formerly healthy pregnant women. This was accompanied by lower IL2 concentrations in plasma from formerly preeclamptic compared to formerly healthy pregnant women. The lower activated proportions of memory T cells after a preeclamptic pregnancy were not associated with altered memory T cell associated cytokine plasma concentrations. These findings showed lower activation of memory CD4⁺ T cell subsets in and after preeclampsia as compared with healthy pregnancies, which makes their implication in the preeclampsia recurrence risk likely.