Type I natural killer T cells: naturally born for fighting

Activation of Invariant Natural Killer T Cells by α-Galactosylceramide Attenuates the Development of Angiotensin II-Mediated Abdominal Aortic Aneurysm in Obese ob/ob Mice

The infiltration and activation of macrophages as well as lymphocytes within the aorta contribute to the pathogenesis of abdominal aortic aneurysm (AAA). Invariant natural killer T (iNKT) cells are unique subset of T lymphocytes and have a crucial role in atherogenesis. However, it remains unclear whether iNKT cells also impact on the development of AAA. Ob/ob mice were administered angiotensin II (AngII, 1,000 ng/kg/min) or phosphate-buffered saline (PBS) by osmotic minipumps for 4 weeks and further divided into 2 groups; α-galactosylceramide (αGC; PBS-αGC; n = 5 and AngII-αGC; n = 12), which specifically activates iNKT cells, and PBS (PBS-PBS; n = 10, and AngII-PBS; n = 6). Maximal abdominal aortic diameter was comparable between PBS-PBS and PBS-αGC, and was significantly greater in AngII-PBS than in PBS-PBS. This increase was significantly attenuated in AngII-αGC without affecting blood pressure. αGC significantly enhanced iNKT cell infiltration compared to PBS-PBS. The ratio of F4/80-positive macrophages or CD3-positive T lymphocytes area to the lesion area was significantly higher in AngII-PBS than in PBS-PBS, and was significantly decreased in AngII-αGC. Gene expression of M2-macrophage specific markers, arginase-1 and resistin-like molecule alpha, was significantly greater in aortic tissues from AngII-αGC compared to AngII-PBS 1 week after AngII administration, and this increase was diminished at 4 weeks. Activation of iNKT cells by αGC can attenuate AngII-mediated AAA in ob/ob mice via inducing anti-inflammatory M2 polarized state. Activation of iNKT cells by the bioactive lipid αGC may be a novel therapeutic target against the development of AAA.

Translating Unconventional T Cells and Their Roles in Leukemia Antitumor Immunity

Recently, cell-mediated immune response in malignant neoplasms has become the focus in immunotherapy against cancer. However, in leukemia, most studies on the cytotoxic potential of T cells have concentrated only on T cells that recognize peptide antigens (Ag) presented by polymorphic molecules of the major histocompatibility complex (MHC). This ignores the great potential of unconventional T cell populations, which include gamma-delta T cells (γδ), natural killer T cells (NKT), and mucosal-associated invariant T cells (MAIT). Collectively, these T cell populations can recognize lipid antigens, specially modified peptides and small molecule metabolites, in addition to having several other advantages, which can provide more effective applications in cancer immunotherapy. In recent years, these cell populations have been associated with a repertoire of anti- or protumor responses and play important roles in the dynamics of solid tumors and hematological malignancies, thus, encouraging the development of new investigations in the area. This review focuses on the current knowledge regarding the role of unconventional T cell populations in the antitumor immune response in leukemia and discusses why further studies on the immunotherapeutic potential of these cells are needed.

Significance of Frequencies, Compositions, and/or Antileukemic Activity of (DC-stimulated) Invariant NKT, NK and CIK Cells on the Outcome of Patients With AML, ALL and CLL

Invariant natural killer T (iNKT)/natural killer (NK)/cytokine-induced killer (CIK) cells are important for immune surveillance. (I) Novel combinations of antibody 6B11 (targeting the Vα24-Jα18-invariant T-cell receptor) with CD4/CD8/CD1d/Vα24 for iNKT subset detection and "T/NK cell-like"-iNKT subsets were defined. Compared with healthy peripheral blood mononuclear cells (MNC) (significantly) lower proportions of iNKT cells (6B11/6B11CD3/6B11CD161), NK cells (CD3CD56/CD3CD161), and CIK cells (CD3CD56/CD3CD161) were found in peripheral blood MNC from acute myeloid (AML)/acute myeloid, lymphoid (ALL)/chronic lymphoid leukemia (CLL) patients in acute disease stages. Subtyping of iNKT cells revealed (significantly) higher proportions of CD3 T cells and CD161 NK cells in AML/ALL/CLL expressing 6B11 compared with healthy MNC. Prognostic evaluations showed higher proportions of iNKT/NK/CIK cells in favorable AML subgroups (younger age, primary, no extramedullary disease, achievement/maintenance of complete remission) or adult ALL and CLL patients. (II) iNKT/NK/CIK cell frequencies increased after (vs. before) mixed lymphocyte cultures of T-cell-enriched immune reactive cells stimulated with MNC/whole blood with or without pretreatment with "cocktails" (dendritic cells generating methods/kits inducing blasts' conversion to leukemia-derived dendritic cells from AML patients). Individual "cocktails" leading to "highest" iNKT cell frequencies could be defined. Antileukemic blast lytic activity correlated significantly with frequencies of iNKT/NK/CIK cells. In summary healthy MNC show significantly more iNKT/NK/CIK cells compared with AML/ALL/CLL MNC, a shift in the iNKT cell composition is seen in healthy versus leukemic samples and iNKT/NK/CIK cell-proportions in AML/ALL/CLL MNC samples correlate with prognosis. "Cocktail"-treated AML blasts lead to higher iNKT/NK/CIK cell frequencies and samples with antileukemic activity show significantly higher frequencies of iNKT/NK/CIK cells. Proportions of iNKT/NK/CIK cells should regularly be evaluated in AML/ALL/CLL diagnosis panels for quantitative/prognostic estimation of individual patients' antileukemic potential and their role in dendritic cells/leukemia-derived dendritic cells triggered immune surveillance.

A brief review of clinical trials involving manipulation of invariant NKT cells as a promising approach in future cancer therapies

In the recent years researchers have put a lot of emphasis on the possible immunotherapeutic strategies able to target tumors. Many studies have proven that the key role in recognition and eradication of cancer cells, both for mice and humans, is being conducted by the invariant natural killer T-cells (NKT). This small subpopulation of lymphocytes can kill other cells, either directly or indirectly, through the natural killer cells’ (NK) activation. They can also swiftly release cytokines, causing the involvement of elements of the innate and acquired immune system. With the discovery of α-galactosylceramide (α-GalCer) – the first known agonist for iNKT cells – and its later subsequent analogs, it became possible to effectively stimulate iNKT cells, hence to keep control over the tumor progression. This article refers to the current knowledge concerning iNKT cells and the most important aspects of their antitumor activity. It also highlights the clinical trials that aim at increasing the amount of iNKT cells in general and in the microenvironment of the tumor. For sure, the iNKT-based immunotherapeutic approach holds a great potential and is highly probable to become a part of the cancer immunotherapy in the future.

[Expression of regulatory T cells and natural killer T cells in peripheral blood of children with Wilms tumor]

OBJECTIVE

To study the changes and clinical significance of CD4⁺CD25⁺CD127^low regulatory T cells (Treg) and CD3⁺CD16⁺CD56⁺ natural killer T cells (NKT) in peripheral blood of children with Wilms tumor.

METHODS

Twenty-one children with Wilms tumor were enrolled as the case group, and twenty-one healthy children for physical examinations were enrolled as the control group. Flow cytometry was used to detect the levels of CD4⁺CD25⁺CD127^low T cells and CD3⁺CD16⁺CD56⁺ T cells in peripheral blood of two groups.

RESULTS

The level of Treg cells in peripheral blood of the case group was significantly lower than in the control group (p<0.05). The level of NKT cells in peripheral blood of the case group was significantly higher than in the control group (p<0.05).

CONCLUSIONS

Treg cells and NKT cells play important roles in the occurrence and development of Wilms tumor. Treg cells and NKT cells may be useful indexes for evaluating immunological function in children with Wilms tumor.

Percentages of NKT cells in the tissues of patients with non-small cell lung cancer who underwent surgical treatment

INTRODUCTION

Natural killer T (NKT) cells are involved in the antitumor response by direct cytotoxicity and indirectly through activation of effector cells. Recent studies have shown a relationship between the number and function of NKT cells and clinical outcomes. NKT cells seem to represent a promising tool for immunotherapy of cancer.

THE AIM OF THE STUDY

The aim of the study was to evaluate the distribution of NKT cells in peripheral blood, lymph nodes and tumor tissue of non-small cell lung cancer (NSCLC) patients, as well as development of the most efficient set of cytokines stimulating differentiation of NKT cells.

MATERIAL AND METHODS

We evaluated the percentage of iNKT+CD3+ cells in the tissues collected from patients with NSCLC. For the generation of NKT cells, we cultured cells isolated from the blood of 20 healthy donors and from the tissues of 4 NSCLC patients. Cells were stimulated with α-GalCer in combinations with cytokines.

RESULTS

We noted significant differences in the percentages of NKT cells in the patients' tissues. The highest percentage of these cells was observed in the tumor tissue and the lowest in the lymph nodes. In vitro, in healthy donors all α-GalCer-cytokine combinations were effective in stimulation of NKT cells' proliferation. NKT cells' proliferation was the most efficiently stimulated by α-GalCer+IL-2+IL-7 and α-GalCer+IL-2+IFN-γ.

CONCLUSIONS

Our results suggest that in the course of NSCLC, NKT cells migrate to the primary tumor and accumulate therein. All tested combinations of α-GalCer and cytokines were capable of generation of NKT cells in vitro.

The role of invariant NKT cells in liver transplant tolerance in rats

OBJECTIVE

The aim of this study was to investigate the role of invariant natural killer T (iNKT) cells in liver transplant tolerance in rats.

METHODS

Animals were randomly divided into 3 groups. The α-galactosylceramide (α-GalCer) group underwent injection through the caudal vein; the saline group received the same dose of saline and the control group received no treatment. Ten rats in each group were examined for survival the others were humanely killed on the seventh day posttransplantation. Liver tissues were used to assess histopathologic changes. Real-time polymerase chain reaction (PCR) was performed to determine the relative expressions of messanger RNAs of Th1/Th2-related cytokine (mRNAs) in the liver allograft. The serum levels of related cytokines were determined using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Allograft survival was significantly higher among the α-galactosylceramide α-GalCer group than the saline or control groups. The histopathology showed mild changes in the α-galactosylceramide α-GalCer compared with the other 2 groups. Real-time PCR showed the relative expression of Th1-related cytokine interferen (IFN)-γ mRNA to be significantly lower in the α-galactosylceramide α-GalCer compared with the other 2 groups, while the Th2-related cytokine interleukin (IL)-10 mRNA was much higher. The ELISA results confirmed these differential expressions.

CONCLUSION

The iNKT cells may play a pivotal role in liver transplant tolerance due to their regulatory functions on the Th1/Th2 imbalance. iNKT cells should be considered to be significant targets because of their attractive specificity and induction of liver allograft tolerance.

Species-specific activity of glycolipid ligands for invariant NKT cells

The immunomodulatory glycolipid α-galactosylceramide (α-GalCer) binds to CD1d and exhibits potent activity as a ligand for invariant CD1d-restricted natural killer-like T cells (iNKT cells). Structural analogues of α-GalCer have been synthesised to determine which components are required for CD1d presentation and iNKT cell activation, however, to date the importance of the phytosphingosine 4-hydroxyl for iNKT cell activation has been disputed. To clarify this, we synthesised two 4-deoxy α-GalCer analogues (sphinganine and sphingosine) and investigated their ability to activate murine and human iNKT cells. Analysis revealed that the analogues possessed comparable activity to α-GalCer in stimulating murine iNKT cells, but were severely compromised in their ability to stimulate human iNKT cells. Here we determined that species-specific glycolipid activity was due to a lack of recognition of the analogues by the T-cell receptors on human iNKT cells rather than insufficient presentation of the analogues on human CD1d molecules. From these results we suggest that glycolipids developed for potent iNKT cell activity in humans should contain a phytosphingosine base.