Regulation of MHC class I-independent NK cell education by SLAM family receptors

Adaptive immune cells antagonize ILC2 homeostasis via SLAMF3 and SLAMF5

Type 2 innate lymphoid cells (ILC2s) mainly reside in tissues with few lymphoid cells. How their tissue residency is regulated remains poorly understood. This study explores the inhibitory role of SLAM-family receptors (SFRs) on adaptive immune cells in ILC2 maintenance. We observed an increase in the population of ILC2s in Rag1-deficient mice. Homotypic engagement of SFRs between ILC2s and adaptive immune cells was identified as a potential mechanism. SFR deficiency led to an increase in ILC2s. Conditional deletion of SFRs on T and/or B cells led to an increased ILC2 abundance. Mechanistically, as ILC precursors differentiate into ILC2s, SFRs, primarily SLAMF3 and SLAMF5, are inhibitory, which impair IL-7-induced PI3K activation and enhance apoptosis via SHP-1. These findings reveal a mechanism by which adaptive immune cells negatively regulate the homeostasis of ILC2s and contribute to our understanding of the complex interplay between innate and adaptive immune cells in the regulation of immune responses.

Decidual Natural Killer Cells: A Good Nanny at the Maternal-Fetal Interface During Early Pregnancy

Decidual natural killer (dNK) cells are the tissue-resident and major subpopulation of NK cells at the maternal-fetal interface. It has been demonstrated that dNK cells play pivotal roles in pregnancy, including keeping maternal-fetal immune tolerance, promoting extravillous trophoblast (EVT) cell invasion, and driving uterine spiral artery remodeling. However, the molecular mechanisms haven't been elucidated until recent years. In this review, we systemically introduce the generation, subsets, and surface or soluble molecules of dNK cells, which are critical for maintaining the functions of dNK cells. Further, new functions of dNK cells including well-controlled cytotoxicity, immunosurveillance and immunotrophism supporting via the cell-cell interaction between dNK cells and EVT cells are mainly focused. The molecular mechanisms involved in these functions are also illustrated. Moreover, pregnancy-associated diseases caused by the dNK cells abnormalities are discussed. It will be important for future investigations about the mechanism of maintenance of pregnancy and parturition and potential clinical applications of dNK cells.