Objective: Preeclampsia is a pregnancy-specific disorder characterized by impaired maternal-fetal immune tolerance. The maternal immune system plays a crucial role in maintaining pregnancy, and its dysfunction is believed to contribute to preeclampsia. Immune checkpoint molecules such as programmed cell death protein 1 (PD-1) and its ligand, programmed death ligand 1 (PD-L1), may play a key role in this process. This study evaluated PD-L1 expression in the placentae of patients with pre-eclampsia (PE) and eclampsia (EC). We also compared PD-L1 expression with histomorphological features and fetal outcomes.

Material and Methods: A prospective case-control study was conducted, including fifty pre-eclampsia cases, twenty-five eclampsia cases, and twenty-five normal pregnancy controls. Detailed clinicopathological data, histomorphological features of the placenta, and fetal outcomes were collected. PD-L1 expression was assessed using immunohistochemistry, with a semi-quantitative scoring system. The relationship between PD-L1 expression, histopathological scores, and fetal outcomes was also evaluated.

Results: In this study, a lower expression of PD-L1 was observed in pre-eclampsia and eclampsia as compared to a normal pregnancy. Adverse fetal outcomes were associated with lower PD-L1 expression and with reduced placental weight and high histopathological scores (>5).

Conclusion: Lower PD-L1 expression was observed in pre-eclampsia and eclampsia compared to normal pregnancies. Reduced PD-L1 expression correlated with histomorphological changes in the placenta and adverse fetal outcomes.