CD4 iNKT Cells Research Articles

CCR2+TREM-1+ monocytes promote natural killer T cell dysfunction contributing towards HBV disease progression.

Natural killer T (NKT) cells are amongst the most important innate immune cells against hepatitis B virus (HBV) infection. Moreover, previous studies have shown that HBV infection induced TREM-1+ expression in monocyte and secretion of inflammatory cytokines. Thus, this prompted us to elucidate the role of TREM-1+ monocytes in regulating the function of iNKT cells. Ninety patients and 20 healthy participants were enrolled in the study. The percentage and phenotype of iNKT cells and TREM-1+ monocytes were measured in the peripheral blood of healthy controls (HC), patients with chronic HBV infection (CHB), HBV-related liver cirrhosis (LC), and HBV-related acute-on-chronic liver failure (ACLF) via flow cytometry. Moreover, co-culture experiments with iNKT cells and TREM-1 overexpressing THP-1 cells were performed to determine the role of TREM-1 in the regulation of NKT cell function. We observed that the percentage of iNKT cells and CD4-iNKT cells gradually decreased, whereas the percentage of CCR2+TREM-1+ monocytes increased with the progression of the disease. In addition, activation of the TREM-1 signaling pathway induced the secretion of inflammatory cytokines leading to pyroptosis of iNKT cells and secretion of IL-17 contributing towards disease progression. Therefore, this study suggests that blocking the activation of TREM-1 in monocytes could promote the elimination of HBV by inhibiting pyroptosis of iNKT cells and restoring their function. However, further studies are required to validate these results that would help in developing new treatment strategies for patients with HBV infections.

Elevated levels of circulating invariant natural killer cell subsets are skewed toward Th2-like phenotype in children with sickle cell disease

Invariant natural killer T (iNKT) cells are being considered as potential targets for immunotherapeutic strategies in a variety of conditions including sickle cell disease (SCD). However, relatively little is known about the fate of iNKT cell subsets in children with SCD. Herein, quantitative and qualitative analyses of circulating iNKT cell subsets were carried out in 120 children in steady state and 30 healthy controls. Children with SCD displayed significantly elevated levels of circulating iNKT cell subsets with a preferential polarization toward Th2-like cells. The known SCD modifiers did not influence levels of iNKT cell subsets, except that children carrying the Bantu haplotype exhibited elevated levels of CD4iNKT cells, and to a lesser degree CD8iNKT cells. Collectively, these findings indicate that circulating iNKT cell subsets are significantly increased in children with SCD, and highlight the existence of imbalanced production of cytokines toward Th2-like phenotype, which seems to be associated with genetic polymorphisms.

Invariant Natural Killer T Cells Ameliorate Monosodium Urate Crystal-Induced Gouty Inflammation in Mice.

Gout is an inflammatory arthritis caused by deposition of intra-articular monosodium urate (MSU) crystal. Previous studies have focused on resident macrophage, infiltrating monocyte, and neutrophil responses to MSU crystal; yet the mechanisms of cellular changes and the potential involvement of other regulatory immune cells remain largely unknown. Invariant natural killer T (iNKT) cells, an innate type of T cell, are involved in the development of various inflammatory diseases. Here, we investigate the role of iNKT cells in MSU crystal-induced gouty inflammation. MSU crystal-induced inflammatory profiles in an air-pouch model were examined in iNKT-deficient CD1d knockout (KO) and wild-type (WT) control mice. To explore potential mechanisms of iNKT cell regulation of gouty inflammation, we cocultured CD4+ or CD4− iNKT cells with bone marrow-derived macrophages (BMDMs). We found that iNKT cells quickly migrated to the site of inflammation upon MSU crystal stimulation in WT mice. The total number of infiltrating cells in CD1d KO mice, especially neutrophils, was dramatically increased at 6 and 12 h (P < 0.01) post-MSU crystal challenge, compared with WT controls. BMDMs cocultured with CD4+ iNKT cells produced less tumor necrosis factor-α and expressed higher levels of M2 macrophage markers, including Clec7a, Pdcd1Ig2, and interleukin-4 (P < 0.01), compared with BMDMs cocultured with CD4− iNKT cells or conventional CD4+ T cells. CD4+ iNKT cells are one of the key regulators of MSU crystal-induced gouty inflammation through the control of macrophage polarization. iNKT cells may serve as a new therapeutic target for gout.

Negative Checkpoint Regulatory Molecule 2B4 (CD244) Upregulation Is Associated with Invariant Natural Killer T Cell Alterations and Human Immunodeficiency Virus Disease Progression.

The CD1d-restricted invariant natural killer T (iNKT) cells are implicated in innate immune responses against human immunodeficiency virus (HIV). However, the determinants of cellular dysfunction across the iNKT cells subsets are seldom defined in HIV disease. Herein, we provide evidence for the involvement of the negative checkpoint regulator (NCR) 2B4 in iNKT cell alteration in a well-defined cohort of HIV-seropositive anti-retroviral therapy (ART) naïve, ART-treated, and elite controllers (ECs). We report on exaggerated 2B4 expression on iNKT cells of HIV-infected treatment-naïve individuals. In sharp contrast to CD4−iNKT cells, 2B4 expression was significantly higher on CD4+ iNKT cell subset. Notably, an increased level of 2B4 on iNKT cells was strongly correlated with parameters associated with HIV disease progression. Further, iNKT cells from ART-naïve individuals were defective in their ability to produce intracellular IFN-γ. Together, our results suggest that the levels of 2B4 expression and the downstream co-inhibitory signaling events may contribute to impaired iNKT cell responses.

Th1 and Th17 proinflammatory profile characterizes invariant natural killer T cells in virologically suppressed HIV+ patients with low CD4+/CD8+ ratio.

Scanty data exist on the phenotype and functionality of invariant natural killer T (iNKT) cells in HIV-infected (HIV+) patients. By flow cytometry, we studied iNKT cells from 54 HIV+ patients who started combined antiretroviral therapy and had undetectable viral load for more than 1 year. Twenty-five maintained a CD4/CD8 ratio less than 0.4, whereas 29 reached a ratio more than 1.1; 32 age-matched and sex-matched patients were healthy controls (CTR). Patients with low ratio had lower percentage of CD4 iNKT cells compared with patients with high ratio and higher CD8 iNKT cell percentage; double-negative iNKT cells were lower in HIV+ patients compared with CTR. Patients with low ratio had higher percentage of CD4 and double-negative iNKT cells expressing CD38 and HLA-DR compared with patients with high ratio. CD4 iNKT cells expressing PD-1 were higher in patients with CD4/CD8 ratio less than 0.4, whereas double-negative iNKT cells expressing PD-1 were lower compared with patients with ratio more than 1.1. Patients with low ratio had higher CD4 iNKT cells producing IL-17, CD8 iNKT cells producing IFN-γ, TNF-α or IFN-γ and TNF-α, and double-negative iNKT cells producing IL-17 or IL-17 and IFN-γ compared with CTR. Activated CD4 (or CD8) T cells correlated with activated CD4 (or CD8) iNKT cells, as well as the percentages of CD4 (or CD8) T cells expressing PD-1 was correlated to that of CD4 (or CD8) iNKT cells expressing PD-1. Low CD4/CD8 ratio despite effective combined antiretroviral therapy is associated with altered iNKT cell subsets, enhanced activation, and prominent Th1/Th17 proinflammatory profile.

Human CD4&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt; CD8&amp;lt;sup&amp;gt;-&amp;lt;/sup&amp;gt; Invariant Natural Killer T Cells Promote IgG Secretion from B Cells Stimulated by Cross-Linking of Their Antigen Receptors

Immunoglobulin (Ig) M production can be induced by the interaction of thymus-independent type-2 (TI-2) antigen (Ag) with B cell Ag receptors (BCRs) without the involvement of conventional T cells; for IgG production through the same process, however, a second signal is required. Previous studies have reported that invariant natural killer T (iNKT) cells may be responsible for the second signal involved in IgG production. In the present study, we addressed whether human iNKT cells could participate in the production of Ig against TI-2 Ag in vitro. Two major distinct subsets of human iNKT cells, CD4+ CD8β- (CD4) and CD4- CD8β- [double negative (DN)] cells, were generated from peripheral blood monocytes from a healthy volunteer. BCR engagement, triggered by anti-IgM antibody stimulation, examined here as a model of BCR engagement triggered by TI-2 Ag, induced abundant IgM production by B cells. Both CD4 and DN iNKT cells reduced IgM production and conversely enhanced IgG production in a dose-dependent manner. In addition, IgG production by CD19+CD27- (naive) and CD19+CD27+ (memory) B cells was predominantly promoted by DNiNKT cells rather than CD4 iNKT cells; nevertheless, IgM production by both B cell subsets was similarly reduced by either subset of iNKT cells. These results suggest that the DN iNKT subsets may preferentially promote Ig class switching by B cells upon stimulation with TI-2 Ag.

Circulating Invariant Natural Killer T Cell Subsets Are Functionally Preserved in Splenectomized Children with Sickle Cell Disease Compared to Patients with Large Spleen

Recent data suggests that invariant natural killer T (iNKT) cells, a unique subset of T lymphocytes that express markers characteristic of both T cells and natural killer cells, play a pivotal role in the pathogenesis of sickle cell disease (SCD). Indeed, these cells are being considered as a potential target to prevent or treat acute crises of SCD in adult patients. However, the phenotypic and functional characteristics of circulating iNKT cell subsets in children with SCD remain unknown. Herein, we functionally evaluated iNKT cell subsets in relation to myeloid dendritic (mDC) and plasmacytoid dendritic (pDC) cells and markers of SCD severity in well-defined groups of children with SCD. The classification criteria for SCD was based on the history of patients, clinical examination, hematological and radiological findings. Blood iNKT cell subsets were prospectively studied in 68 children with SCD and normal controls using peripheral blood mononuclear cells, 10-color flow cytometry and culture assays. The iNKT cell subsets were identified by the positive-staining of Vα24Jα18 T cell receptor alpha chain, along with CD3, CD4 and CD8 surface markers and the intra-cellular cytokine production of interferon-gamma (Th1-like), interleukin-4 (Th2-like) and interleukin-17 (Th17-like) cells. The mDC and pDC cells were phenotypically characterized by the expression of HLA-DR, CD123, CD11c, Lin and CD1d, a non-classical molecule that induces the activation of iNKT cells. SCD patients were stratified into three groups including surgically splenectomized (n=23), large spleen (n=21) and steady state (n=24). Comparisons among study groups were performed using ANOVA and unpaired t test, while the Spearman's correlation was used to assess associations. Compared to normal individuals, splenectomized and steady state subjects, large spleen patients exhibited significantly higher levels of CD3iNKT, CD4iNKT and CD8iNKT cells (P=0.04). There were no differences in the levels of iNKT cell subsets between splenectomized and steady state subjects (P=0.56). The levels of mDC and pDC cells were also similar among the study groups (P=0.70). Interestingly, the large spleen patients tend to have higher CD4, but not CD8, Th1-like, Th2-like and Th17-like iNKT cells compared to splenectomized and steady state subjects (p=0.08). The expression levels of CD1d on both mDC and pDC were equivalent among study groups. The levels of CD3iNKT cells were negatively associated with baseline haemoglobin F levels (r=0.45, P=0.04) but not with age, time since splenectomy, spleen size or total hemoglobin levels at phlebotomy. Collectively, these results further advance the functional characterization of circulating iNKT cell subsets in children with SCD and reveal that surgically splenectomized patients have preserved function of iNKT cell subsets that are to be considered for clinical purposes. DisclosuresNo relevant conflicts of interest to declare.