Id |
Subject |
Object |
Predicate |
Lexical cue |
T119 |
0-21 |
Sentence |
denotes |
Innate Lymphoid Cells |
T120 |
22-188 |
Sentence |
denotes |
Innate lymphoid cells (ILCs) are innate immune effector cells that lack the expression of rearranged antigen receptors (T cell receptor [TCR], B cell receptor [BCR]). |
T121 |
189-369 |
Sentence |
denotes |
The ILC family is divided into two main groups: the cytotoxic natural killer (NK) cells and the non-cytotoxic helper ILCs, which include ILC1, ILC2, and ILC3 (Vivier et al., 2018). |
T122 |
370-524 |
Sentence |
denotes |
Conventional NK cells include CD56brightCD16− NK cells and CD56dimCD16+ cells, which are specialized in cytokine production or cytotoxicity, respectively. |
T123 |
526-593 |
Sentence |
denotes |
NK Cells Are Decreased in the Peripheral Blood of COVID-19 patients |
T124 |
594-826 |
Sentence |
denotes |
Multiple studies have reported reduced numbers of NK cells in the peripheral blood of COVID-19 patients, which is associated with severity of the disease (Song et al., 2020, Wang et al., 2020f, Yu et al., 2020, Zheng et al., 2020b). |
T125 |
827-995 |
Sentence |
denotes |
A recent scRNA-seq analysis revealed a transcriptomic signature for NK cells that was equally represented in lungs from patients and healthy donors (Liao et al., 2020). |
T126 |
996-1197 |
Sentence |
denotes |
The majority of lung NK cells are non-resident (Gasteiger et al., 2015, Marquardt et al., 2017), and CXCR3 has been shown to mediate NK cell infiltration upon influenza infection (Carlin et al., 2018). |
T127 |
1198-1412 |
Sentence |
denotes |
In vitro, CXCR3 ligands (CXCL9-11) are increased in SARS-CoV-2-infected human lung tissue (Chu et al., 2020), and CXCR3-ligand-producing monocytes are expanded in the lungs of COVID-19 patients (Liao et al., 2020). |
T128 |
1413-1558 |
Sentence |
denotes |
This suggests that the CXCR3 pathway might facilitate NK cell recruitment from the peripheral blood to the lungs in COVID-19 patients (Figure 2). |
T129 |
1560-1609 |
Sentence |
denotes |
NK Cell Activation Pathways in Antiviral Immunity |
T130 |
1610-1696 |
Sentence |
denotes |
NK cells express inhibitory and activating receptors that regulate their cytotoxicity. |
T131 |
1697-2011 |
Sentence |
denotes |
They are therefore able to induce the lysis of virus-infected cells that upregulate virus-derived proteins, as well as stress-inducible ligands, which are then recognized by NK-cell-activating receptors, such as NKp46 (Cerwenka and Lanier, 2001, Draghi et al., 2007, Duev-Cohen et al., 2016, Glasner et al., 2012). |
T132 |
2012-2208 |
Sentence |
denotes |
Future studies should investigate the expression of NK receptor ligands on SARS-CoV-2-infected cells in order to better understand the mechanisms underlying NK cell activation in COVID-19 disease. |
T133 |
2209-2516 |
Sentence |
denotes |
Further, secretion of IgG1 and IgG3 antibodies during SARS-CoV-2 infection (Amanat et al., 2020) may induce CD56dim CD16+ NK cell activation through Fc receptor recognition of antibodies either bound to surface antigens expressed on infected cells or to extracellular virions as immune complexes (Figure 2). |
T134 |
2517-2729 |
Sentence |
denotes |
This interaction might trigger both cytokine production by NK cells and lysis of infected cells through antibody-mediated cellular cytotoxicity (ADCC), as shown in influenza infection (Von Holle and Moody, 2019). |
T135 |
2730-2969 |
Sentence |
denotes |
Emerging data highlight the capacity for NK-mediated ADCC in response to naturally isolated SARS-CoV-1 anti-S IgG that crossreacts with SARS-CoV-2 S glycoprotein when transfected into Chinese hamster ovary (CHO) cells (Pinto et al., 2020). |
T136 |
2970-3134 |
Sentence |
denotes |
These findings suggest that triggering NK cell activation may not only contribute to the resolution of infection, but also contribute to the cytokine storm in ARDS. |
T137 |
3136-3190 |
Sentence |
denotes |
Impairment of NK Cell Function in SARS-CoV-2 Infection |
T138 |
3191-3479 |
Sentence |
denotes |
Ex vivo NK cells from peripheral blood of COVID-19 patients have reduced intracellular expression of CD107a, Ksp37, granzyme B, and granulysin, suggesting an impaired cytotoxicity, as well as an impaired production of chemokines, IFN-ɣ, and TNF-α (Wilk et al., 2020, Zheng et al., 2020b). |
T139 |
3480-3545 |
Sentence |
denotes |
Several pathways may contribute to the dysregulation of NK cells. |
T140 |
3546-3788 |
Sentence |
denotes |
While influenza virus infects NK cells and induces apoptosis (Mao et al., 2009), lung NK cells do not express the entry receptor for SARS-CoV-2, ACE2, and are therefore unlikely to be directly infected by SARS-CoV-2 (Travaglini et al., 2020). |
T141 |
3789-4106 |
Sentence |
denotes |
The majority of NK cells found in human lung display a mature CD16+KIR+CD56dim phenotype and are able to induce cell cytotoxicity in response to loss of human leukocyte antigen (HLA) class I or through Fc receptor signaling, although to a lower extent than their peripheral blood counterpart (Marquardt et al., 2017). |
T142 |
4107-4321 |
Sentence |
denotes |
Killer-immunoglobulin receptors (KIRs) are acquired during NK cell development alongside CD16 (FcRγIIIA) and are essential for NK cell licensing and subsequent capacity for cytolytic function (Sivori et al., 2019). |
T143 |
4322-4500 |
Sentence |
denotes |
Frequencies of NK cells expressing CD16 and/or KIRs are decreased in the blood following SARS-CoV-2 and SARS-CoV-1 infection, respectively (Xia et al., 2004, Wang et al., 2020d). |
T144 |
4501-4708 |
Sentence |
denotes |
Collectively, the data suggest either an impaired maturation of the NK compartment or migration of the mature, circulating NK cells into the lungs or other peripheral tissues of SARS-CoV-2-infected patients. |
T145 |
4709-4823 |
Sentence |
denotes |
The immune checkpoint NKG2A is increased on NK cells and CD8 T cells from COVID-19 patients (Zheng et al., 2020b). |
T146 |
4824-5049 |
Sentence |
denotes |
NKG2A inhibits cell cytotoxicity by binding the non-classical HLA-E molecule (Braud et al., 1998, Brooks et al., 1997), and this interaction is strongly correlated with poor control of HIV-1 infection (Ramsuran et al., 2018). |
T147 |
5050-5202 |
Sentence |
denotes |
Genes encoding the inhibitory receptors LAG3 and TIM3 are also upregulated in NK cells from COVID-19 patients (Wilk et al., 2020, Hadjadj et al., 2020). |
T148 |
5203-5283 |
Sentence |
denotes |
Thus, increased immune checkpoints on NK cells might contribute to viral escape. |
T149 |
5284-5479 |
Sentence |
denotes |
Additionally, COVID-19 patients have higher plasma concentrations of IL-6 (Huang et al., 2020b), which significantly correlate with lower NK cell numbers (Wang et al., 2020d, Wang et al., 2020f). |
T150 |
5480-5748 |
Sentence |
denotes |
In vitro stimulation by IL-6 and soluble IL-6 receptor has previously revealed impaired cytolytic functions (perforin and granzyme B production) by healthy donor NK cells, which can be restored following addition of tocilizumab (IL-6R blockade) (Cifaldi et al., 2015). |
T151 |
5749-6006 |
Sentence |
denotes |
TNF-α is also upregulated in the plasma of COVID-19 patients (Huang et al., 2020b), and ligand-receptor interaction analysis of peripheral blood scRNA-seq data suggests that monocyte-secreted TNF-α might bind to its receptors on NK cells (Guo et al., 2020). |
T152 |
6007-6230 |
Sentence |
denotes |
TNF-α is known to contribute to NK cell differentiation (Lee et al., 2009), which includes downregulation of NKp46 (Ivagnès et al., 2017), though no effect of TNF-α or IL-6 on NK cell-mediated ADCC has been reported so far. |
T153 |
6231-6488 |
Sentence |
denotes |
Collectively, these data suggest that crosstalk with monocytes might impair NK cell recognition and killing of SARS-CoV-2-infected cells, and antibodies targeting IL-6 and TNF-signaling may benefit enhanced NK cell functions in COVID-19 patients (Figure 2). |
T154 |
6490-6539 |
Sentence |
denotes |
Relevance for Helper ILCs in SARS-CoV-2 Infection |
T155 |
6540-6629 |
Sentence |
denotes |
No studies, to date, have reported ILC1, ILC2, or ILC3 functions in SARS-CoV-2 infection. |
T156 |
6630-6722 |
Sentence |
denotes |
All three subsets are present in healthy lung (De Grove et al., 2016, Yudanin et al., 2019). |
T157 |
6723-6933 |
Sentence |
denotes |
ILC2s are essential for the improvement of lung function following influenza infection in mice through amphiregulin-mediated restoration of the airway epithelium and oxygen saturation (Monticelli et al., 2011). |
T158 |
6934-7094 |
Sentence |
denotes |
However, ILC2s also produce IL-13, contributing to the recruitment of macrophages to the lung and influenza-induced airway hyperreactivity (Chang et al., 2011). |
T159 |
7095-7265 |
Sentence |
denotes |
Indeed, ILCs are involved in the polarization of alveolar macrophages, either toward a M1-like phenotype (ILC1 and ILC3) or a M2-like phenotype (ILC2) (Kim et al., 2019). |
T160 |
7266-7491 |
Sentence |
denotes |
Given the increased IL-13 concentrations (Huang et al., 2020b) and the dysregulation of the macrophage compartment observed in COVID-19 patients, the role played by ILCs in SARS-CoV-2 infection warrants further investigation. |