NK cells detect changes in adaptive immunity within mouse decidua from gestation day eight

Area of Science:

• Reproductive Immunology
• Cellular Immunology
• Maternal-Fetal Interface Biology

Background:

• Human peripheral blood Natural Killer (NK) cells (CD56+ CD16-) interact with mouse decidua basalis.
• NK cell adhesion to decidual tissue shows gender-specific cyclical variation in women, suggesting menstrual cycle-dependent homing potential.
• NK cell adhesion increases significantly with later gestational timepoints.

Purpose of the Study:

• To investigate the cellular triggers for human NK cell clustering on mouse decidua basalis at different gestational days.
• To determine if myeloid dendritic cells (mDCs) or lymphocytes within the decidua are responsible for activating NK cell clustering.

Main Methods:

• In vitro adhesion assays using human peripheral blood NK cells and cryostat sections of mouse decidua basalis at various gestational days (gd7, gd8, gd9).
• Utilized transgenic mice expressing eYFP in mDCs to assess mDC involvement.
• Employed alymphoid mice and decidua lacking T and B cells to identify the specific lymphocyte subsets responsible for NK cell activation.

Main Results:

• Human CD56+ CD16- NK cells transitioned from single-cell adhesion on gd7 decidua to forming large clusters on gd8 and gd9 decidua.
• NK cell clustering was independent of contact with mDCs.
• Clustering behavior required the presence of substrate lymphocytes, specifically identifying decidual T and/or B lymphocytes as activators.

Conclusions:

• Decidual T and/or B lymphocytes, not mDCs, are responsible for the observed NK cell clustering response.
• This interaction occurs just prior to spiral artery modification, implicating adaptive decidual immune responses in regulating NK cell function.
• The findings suggest a crucial role for adaptive immunity in modulating NK cell activity at the maternal-fetal interface.