Reciprocal regulation of human natural killer cells and macrophages associated with distinct immune synapses

Abstract

IntroductionNatural killer (NK) cells are important effector cells of the innate immune response through their production of cytokines and lysis of transformed or infected cells without prior sensitization. NK cells exert killing by sensing "missing self" and/or by triggering of activating receptors upon interaction with specific ligands. 1 One of the best-characterized activating receptors is NKG2D, expressed on NK, NKT, and T cells, which recognizes stress-inducible class I major histocompatibility complex (MHC)-like proteins. 2 Other activating receptors, natural cytotoxicity receptors (NCRs), are expressed almost exclusively on NK cells. 3 Ligands for activating NK cell receptors are found on many cancer cell lines 4 and cells infected with bacteria 5 or viruses. [6][7][8] Immunoregulatory crosstalk between NK cells and dendritic cells (DCs) has emerged as important in both innate and adaptive immune responses. 9,10 However, the extent of crosstalk between human NK cells and macrophages has been less studied. Macrophages are also important effector cells of the innate immune response, exerting their function by using a range of receptors that recognize pathogen molecules such as bacterial lipopolysaccharide (LPS). 11 LPS is a powerful endotoxin that activates macrophages, although at high doses macrophages become refractory to further stimulation (ie, endotolerant). 12 Here, we set out to examine the potential for immunoregulatory crosstalk between human NK cells and macrophages or macrophages activated with LPS and probe the molecular basis for this.At the intercellular contact between immune cells, proteins are commonly seen to segregate into central and peripheral supramolecular activating clusters (c-and p-SMACs) at the immune synapse (IS). Functions of the NK cell IS could be to provide a framework for establishing checkpoints for cellular activation and/or directing secretion of lytic granules or cytokines in some circumstances. [13][14][15] Here we define, for the first time, 2 distinct NK cell-activating synapses. The macrophage-NK cell IS associated with priming, but not triggering, NK cytolysis and the IS between NK cells and macrophages treated with a high dose of LPS that triggers NK cytolysis. Materials and methods Generation of macrophages and DCsPeripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation (Ficoll-Paque Plus; Amersham Pharmacia Biotech, Piscataway, NJ). Serum was collected, heat inactivated for 30 minutes at 56°C, and filtered. PBMCs were incubated for 2 hours in plastic plates An Inside Blood analysis of this article appears at the front of this issue.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. For personal use only. on March 31, 2019. by guest www.bloodjournal.org From previously coated overnight with 2% gelatin (Sigma-Aldrich, St Louis, MO). After 2 hours, the flask was was...

The interaction of human natural killer cells with either unpolarized or polarized macrophages results in different functional outcomes

“…NKp46 participates mainly to the induction of cytotoxicity against macrophages, whereas, in line with a previous report (30), 2B4 would be primarily involved in the induction of IFN-γ secretion. On the other hand, DNAM-1 plays a dual role being involved in the induction of both cytolytic activity and IFN-γ production.…”

Post-translational Modification of the NKG2D Ligand RAET1G Leads to Cell Surface Expression of a Glycosylphosphatidylinositol-linked Isoform

“…Levels of protein expression of RAET1G in the cell lines might not be sufficient to be detected by the antibody in Western blotting or FACS, and expression might only be increased on receipt of certain signals, such as viral infection or DNA damage. There are other reports demonstrating that different cells and tissues express NKG2D ligand transcripts but lack corresponding protein expression (22)(23)(24)(25)(26). Clearly, NKG2D ligand expression is subject to complex regulation at several levels: the transcriptional level, the post-transcriptional level by microRNAs (14), and at post-translational level, for example the processing of RAET1G as we have reported here and the S-acylation of MICA (27).…”

Herpesvirus Seropositivity in Childhood Associates with Decreased Monocyte-Induced NK Cell IFN-γ Production

“…To our knowledge, IFN-␥ has no clear involvement in regulation of CD16 on monocytes (43,44). Furthermore, NK cells can be regulatory by killing immature DCs (45) or overactivated macrophages (46), but whether preferential elimination of the CD14 ϩ CD16 ϩ cells could be an explanation behind decreased proportions in SP children remains to be elucidated.…”