Decoding the maternal-fetal dialogue: NK cell education in reproductive outcomes†

Natural killer (NK) cell education, a dynamic and finely tuned process, is essential for calibrating decidual NK (dNK) cell responsiveness at the maternal-fetal interface. This education process, governed by distinct receptor-ligand interactions, refines dNK cell function to maintain immune tolerance while preserving responsiveness to pathological threats. Killer-cell immunoglobulin-like receptors (KIRs) interacting with human leukocyte antigen (HLA)-C dictate a balance between activation and inhibition, shaping dNK cell adaptability to maternal-fetal genetic variation. The NKG2A-HLA-E axis establishes a foundational inhibitory checkpoint, ensuring immune tolerance through metabolic and functional programming. LILRB1-HLA-G interactions promote immunomodulatory and angiogenic functions crucial for placental development, while SLAM family receptors (SFRs), including 2B4-CD48, modulate activation thresholds and restrain excessive cytotoxicity. Disruptions in these finely orchestrated pathways contribute to recurrent implantation failure, pregnancy loss, and preeclampsia. This review synthesizes the diverse mechanisms of NK cell education, highlighting how specific receptor-ligand interactions regulate dNK cell function and maternal-fetal immune adaptation. A deeper understanding of these pathways not only enhances our comprehension of reproductive immunology but also paves the way for novel therapeutic strategies targeting immune dysregulation in pregnancy-related disorders.