Natural Killer Cell Signaling Pathways Vivier, Eric; Nunès, Jacques A.; Vély, Frédéric
Science (American Association for the Advancement of Science),
11/2004, Letnik:
306, Številka:
5701
Journal Article
Recenzirano
Natural killer (NK) cells are lymphocytes of the innate immune system that are involved in the early defenses against foreign cells, as well as autologous cells undergoing various forms of stress, ...such as microbial infection or tumor transformation. NK cell activation is controlled by a dynamic balance between complementary and antagonistic pathways that are initiated upon interaction with potential target cells. NK cells express an array of activating cell surface receptors that can trigger cytolytic programs, as well as cytokine or chemokine secretion. Some of these activating cell surface receptors initiate protein tyrosine kinase (PTK)-dependent pathways through noncovalent associations with transmembrane signaling adaptors that harbor intracytoplasmic ITAMs (immunoreceptor tyrosine-based activation motifs). Additional cell surface receptors that are not directly coupled to ITAMs also participate in NK cell activation. These include NKG2D, which is noncovalently associated to the DAP10 transmembrane signaling adaptor, as well as integrins and cytokine receptors. NK cells also express cell surface inhibitory receptors that antagonize activating pathways through protein tyrosine phosphatases (PTPs). These inhibitory cell surface receptors are characterized by intracytoplasmic ITIMs (immunoreceptor tyrosine-based inhibition motifs). The tyrosine-phosphorylation status of several signaling components that are substrates for both PTKs and PTPs is thus key to the propagation of the NK cell effector pathways. Understanding the integration of these multiple signals is central to the understanding and manipulation of NK cell effector signaling pathways.
The programmed death-1 (PD-1) molecule is involved in peripheral tolerance and in the immune escape mechanisms during chronic viral infections and cancer. PD-1 interacts with two ligands, PD-L1 and ...PD-L2. We have investigated the molecular mechanisms of PD-1 interactions with its ligands by surface plasmon resonance and cell surface binding as well as the ability of the two ligands to compete for PD-1 binding. PD-L1 and PD-L2 bound PD-1 with comparable affinities, but striking differences were observed at the level of the association and dissociation characteristics. PD-L1, but not PD-L2, had a delayed interaction reminiscent of a phenomenon of conformational transition. These mechanisms were confirmed by using PD-L1 mAbs that delayed the dissociation of PD-L1 from PD-1. This mechanism was not restricted to PD-1 binding since PD-L1 behaved in a similar manner with its second ligand, CD80. Finally, we could demonstrate that PD-L1 and PD-L2 competed for PD-1 binding and conversely, an antagonist PD-1 mAb blocked both PD-L1 and PD-L2 binding to PD-1 and strongly enhanced T-cell proliferation. These data further emphasize the differential molecular mechanisms of interaction of PD-L1 and PD-L2 with PD-1, and suggest possible new approach for the therapy of chronic infection, cancer and transplantation.
Abstract Targeting intracellular inhibiting proteins has been revealed to be a promising strategy to improve CD8 + T cell anti-tumor efficacy. Here, we are focusing on intracellular inhibiting ...proteins specific to TCR signaling: DOK1 and DOK2 expressed in T cells. We hypothesized that depletion of intracellular inhibition checkpoint DOK1 and DOK2 could improve CD8 + T-cell based cancer therapies. To evaluate the role of DOK1 and DOK2 depletion in physiology and effector function of CD8 + T lymphocytes and in cancer progression, we established a transgenic T cell receptor mouse model specific to melanoma antigen hgp100 (pmel-1 TCR Tg) in WT and Dok1 / Dok2 DKO (double KO) mice. We showed that both DOK1 and DOK2 depletion in CD8 + T cells after an in vitro pre-stimulation induced a higher percentage of effector memory T cells as well as an up regulation of TCR signaling cascade- induced by CD3 mAbs, including the increased levels of pAKT and pERK, two major phosphoproteins involved in T cell functions. Interestingly, this improved TCR signaling was not observed in naïve CD8 + T cells. Despite this enhanced TCR signaling essentially shown upon stimulation via CD3 mAbs, pre-stimulated Dok1 / Dok2 DKO CD8 + T cells did not show any increase in their activation or cytotoxic capacities against melanoma cell line expressing hgp100 in vitro. Altogether we demonstrate here a novel aspect of the negative regulation by DOK1 and DOK2 proteins in CD8 + T cells. Indeed, our results allow us to conclude that DOK1 and DOK2 have an inhibitory role following long term T cell stimulations.
The antitumor activity of exercise by means of enhanced immune activation is documented, but better identification of the underlying mechanisms is required to develop new therapeutic strategies. ...Recent work from the Dr Bar-Sagi group reveals that exercise engages IL-15 signaling and pharmacological activation of the IL-15/IL-15R axis mimics the exercise-driven immune cell-mediated cytotoxicity in pancreatic cancer.
• The cosignaling molecule, PD-L2 is expressed on human activated T cell subsets. • The PD-L2 triggering down-regulates (TCR+CD28)-induced cytokine production on human T cells. • A direct targeting ...of PD-L2 on T cells blocks T cell proliferation.
T-cell activation and proliferation are regulated by cosignaling adhesion molecules involved in positive or negative signals. Programmed death (PD)-1 is one of immune inhibitory molecules that is expressed in activated T cells and is a promising target for immunotherapy. Both PD-1 ligands, PD-L1 and PD-L2 are expressed on antigen presenting cells (APCs) involved in the dialogue between a T cell and an APC. Here, we analysed the expression of these ligands, especially for PD-L2, on T cells. PD-L2 appears to be expressed on activated CD4 and CD8T cell subsets. Moreover, as PD-1 molecule, PD-L2 engagement at the surface of T cells is able to down-modulate cytokine production and cell proliferation. These observations indicate that PD-L2 is expressed following activation and is involved in the regulation of T cell function, highlighting the level of complexity in the T cell cosignaling network.
The relationship between COVID-19 severity and cancer immunity and immunotherapy is not fully understood. While there is evidence suggesting that COVID-19 may have an impact on the immune system of ...cancer patients (1), the exact mechanism and the implications for treatment with immunotherapy are not well known. Importantly, cancer patients may have an increased risk for more severe COVID-19 disease due to their weakened immune system (2). In fact, patients undergoing anti-cancer treatment, especially immunotherapy, that also have baseline underlying immunosuppression, have particularly poor COVID-19 outcomes (3). In addition, vaccination against COVID-19 has not resulted in long lasting immunity in cancer patients necessitating boosters for best response (4). Therefore, dedicated research to determine the mechanism in which COVID-19 affects cancer immunity and immunotherapy is needed. In this Research Topic (RT), several authors investigated pivotal aspects of COVID-19 severity in the context of cancer immunotherapy.
Significance
This work provides a report of accumulation of unconventional CD56
−
CD16
+
NK cells in nonvirally induced malignancies. Increased frequency of CD56
−
CD16
+
NK cells is associated with ...adverse clinical outcome in AML, as well as other maturation defects, and might contribute to a defective control of AML progression. Pseudotime analysis highlights a disruption in the maturation process of conventional NK cells in AML patients, leading to a bifurcation point absent in healthy subjects. This analysis, combined with the reduced frequency of conventional NK cells observed in AML patients, suggests that unconventional CD56
−
CD16
+
NK cells derive from an aberrant maturation of conventional NK cells. Overall, accumulation of CD56
−
CD16
+
NK cells could be an important feature of immune escape from innate immunity.
Natural killer (NK) cells are major antileukemic immune effectors. Leukemic blasts have a negative impact on NK cell function and promote the emergence of phenotypically and functionally impaired NK cells. In the current work, we highlight an accumulation of CD56
−
CD16
+
unconventional NK cells in acute myeloid leukemia (AML), an aberrant subset initially described as being elevated in patients chronically infected with HIV-1. Deep phenotyping of NK cells was performed using peripheral blood from patients with newly diagnosed AML (
n
= 48, HEMATOBIO cohort, NCT02320656) and healthy subjects (
n
= 18) by mass cytometry. We showed evidence of a moderate to drastic accumulation of CD56
−
CD16
+
unconventional NK cells in 27% of patients. These NK cells displayed decreased expression of NKG2A as well as the triggering receptors NKp30 and NKp46, in line with previous observations in HIV-infected patients. High-dimensional characterization of these NK cells highlighted a decreased expression of three additional major triggering receptors required for NK cell activation, NKG2D, DNAM-1, and CD96. A high proportion of CD56
−
CD16
+
NK cells at diagnosis was associated with an adverse clinical outcome and decreased overall survival (HR = 0.13;
P
= 0.0002) and event-free survival (HR = 0.33;
P
= 0.018) and retained statistical significance in multivariate analysis. Pseudotime analysis of the NK cell compartment highlighted a disruption of the maturation process, with a bifurcation from conventional NK cells toward CD56
−
CD16
+
NK cells. Overall, our data suggest that the accumulation of CD56
−
CD16
+
NK cells may be the consequence of immune escape from innate immunity during AML progression.
We created APC-mimetic synthetic substrates to study the impact of ligand clustering on T cell activation and spreading. The substrates exhibit antibodies directed against the TCR-complex in the form ...of a patterned array of sub micrometric dots surrounded by a fluid supported lipid bilayer (SLB) which may itself be functionalized with another bio-molecule. We show that for T cell adhesion mediated by T cell receptor (TCR) alone, in the patterned, but not in the corresponding homogeneous controls, the TCR, ZAP-70 and actin are present in the form of clusters or patches that co-localize with the ligand-dots. However, global cell scale parameters like cell area and actin distribution are only weakly impacted by ligand clustering. In presence of ICAM-1 - the ligand of the T cell integrin LFA-1 - on the SLB, the TCR is still clustered due to the patterning of its ligands, but now global parameters are also impacted. The actin organization changes to a peripheral ring, resembling the classical actin distribution seen on homogeneous substrates, the patterned membrane topography disappears and the membrane is flat, whereas the cell area increases significantly. These observations taken together point to a possible pivotal role for LFA-1 in amplifying the effect of TCR-clustering. No such effect is evident for co-engagement of CD28, affected
its ligand B7.2. Unlike on ICAM-1, on B7.2 cell spreading and actin organization are similar for homogeneous and patterned substrates. However, TCR and ZAP-70 clusters are still formed in the patterned case. These results indicate complementary role for LFA-1 and CD28 in the regulation and putative coupling of TCR micro-clusters to actin. The engineered substrates presented here clearly have the potential to act as platform for fundamental research in immune cell biology, as well as translational analyses in immunotherapy, for example to screen molecules for their role in T cell adhesion/activation.
Crosslinking of regulatory immunoreceptors (RR), such as BDCA-2 (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses production of type-I interferon (IFN)-α/β and ...other cytokines in response to Toll-like receptor (TLR) 7/9 ligands. This cytokine-inhibitory pathway is mediated by spleen tyrosine kinase (Syk) associated with the ITAM-containing adapter of RR. Here we demonstrate by pharmacological targeting of Syk that in addition to the negative regulation of TLR7/9 signaling via RR, Syk also positively regulates the TLR7/9 pathway in human pDCs. Novel highly specific Syk inhibitor AB8779 suppressed IFN-α, TNF-α and IL-6 production induced by TLR7/9 agonists in primary pDCs and in the pDC cell line GEN2.2. Triggering of TLR9 or RR signaling induced a differential kinetics of phosphorylation at Y352 and Y525/526 of Syk and a differential sensitivity to AB8779. Consistent with the different roles of Syk in TLR7/9 and RR signaling, a concentration of AB8779 insufficient to block TLR7/9 signaling still released the block of IFN-α production triggered via the RR pathway, including that induced by hepatitis B and C viruses. Thus, pharmacological targeting of Syk partially restored the main pDC function-IFN-α production. Opposing roles of Syk in TLR7/9 and RR pathways may regulate the innate immune response to weaken inflammation reaction.
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