Two Distinct Myeloid Subsets at the Term Human Fetal-Maternal Interface.

Area of Science:

• Immunology
• Reproductive Biology
• Cell Biology

Background:

• Immune cells, including NK cells and macrophages, are crucial during pregnancy, performing vital roles like spiral artery remodeling and immune tolerance.
• It remains debated whether these functions are carried out by a single cell type or distinct subsets.

Purpose of the Study:

• To identify and characterize distinct subsets of myeloid cells within the placenta.
• To investigate the differential immune-modulating and pro-inflammatory capacities of these myeloid subsets.

Main Methods:

• Isolation and characterization of placental myeloid cell subsets.
• Analysis of cytokine production (IL-10, IL-1β, IL-6) and expression of inhibitory receptors (e.g., programmed cell death 1 ligands).

Main Results:

• Two distinct myeloid cell subsets were identified based on their functional capacities.
• One subset primarily produces the regulatory cytokine IL-10, while the other secretes pro-inflammatory mediators IL-1β and IL-6.
• Regulatory myeloid cells express high levels of inhibitory receptors, including programmed cell death 1 (PD1) ligands.

Conclusions:

• Distinct myeloid cell subsets exist in the placenta with differing immune regulatory and inflammatory potentials.
• The PD1/PD1 ligands pathway may play a critical role in maintaining immune tolerance during human pregnancy.