Flow cytometry for natural killer T cells: multi-parameter methods for multifunctional cells

Natural Killer T (NKT) Cells in Autoimmune Hepatitis: Current Evidence from Basic and Clinical Research

Natural killer T (NKT) cells are unconventional T cells that are activated by glycolipid antigens. They can produce a variety of inflammatory and regulatory cytokines and, therefore, modulate multiple aspects of the immune response in different pathological settings, including autoimmunity. NKT cells have also been implicated in the immunopathogenesis of autoimmune hepatitis, and in this review we summarize and analyze the main studies investigating the involvement and/or homeostasis of NKT cells in this disease. In detail, the evidence from both basic and clinical research has been specifically analyzed. Even though the experimental murine models supported a relevant role of NKT cells in immune-mediated hepatic injury, very few studies specifically investigated NKT cell homeostasis in patients with autoimmune hepatitis; however, these initial studies reported some alterations of NKT cells in these patients, which may also correlate with the disease activity to some extent. Further clinical studies are needed to investigate the potential role and use of NKT cell analysis as a disease marker of clinical relevance, and to better understand the precise cellular and molecular mechanisms by which NKT cells contribute to the pathogenesis of autoimmune hepatitis.

The Role of Natural Killer T Cells in Cancer-A Phenotypical and Functional Approach

Natural killer T (NKT) cells are a subset of CD1d-restricted T cells at the interface between the innate and adaptive immune system. NKT cells can be subdivided into functional subsets that respond rapidly to a wide variety of glycolipids and stress-related proteins using T- or natural killer (NK) cell-like effector mechanisms. Because of their major modulating effects on immune responses via secretion of cytokines, NKT cells are also considered important players in tumor immunosurveillance. During early tumor development, T helper (T_H)1-like NKT cell subsets have the potential to rapidly stimulate tumor-specific T cells and effector NK cells that can eliminate tumor cells. In case of tumor progression, NKT cells may become overstimulated and anergic leading to deletion of a part of the NKT cell population in patients via activation-induced cell death. In addition, the remaining NKT cells become hyporesponsive, or switch to immunosuppressive T_H2-/T regulatory-like NKT cell subsets, thereby facilitating tumor progression and immune escape. In this review, we discuss this important role of NKT cells in tumor development and we conclude that there should be three important focuses of future research in cancer patients in relation with NKT cells: (1) expansion of the NKT cell population, (2) prevention and breaking of NKT cell anergy, and (3) skewing of NKT cells toward T_H1-like subsets with antitumor activity.

Isolation and Functional Use of Human NKT Cells

This unit details methods for the isolation, in vitro expansion, and functional characterization of human iNKT cells. The term 'iNKT' derives from the fact that a large fraction of murine and some human NK marker+ T cells ('NKT') recognize the MHC class I-like CD1d protein and use an identical 'invariant' TCRα chain, which is generated in humans by precise Vα24 and Jα18 rearrangements with either no N-region diversity or subsequent trimming to identical or nearly identical amino acid sequence (hence, 'iNKT' cells). iNKT are mostly CD4+ or CD4-CD8- ('double negative'), although a few CD8+ iNKT can be found in some humans. Basic Protocol 1 and Alternate Protocol 1 use multi-color FACS analysis to identify and quantitate rare iNKT cells from human samples. Basic Protocol 2 describes iNKT cell purification. Alternate Protocol 2 describes a method for high-speed FACS sorting of iNKT cells. Basic Protocol 3 explains functional analysis of iNKT. Alternate Protocol 3 employs a cell sorting approach to isolate iNKT cell clones. A support protocol for secondary stimulation and rapid expansion of iNKT cells is also included. © 2017 by John Wiley & Sons, Inc.

Subpopulations of natural killer-T-like cells before and after surgical treatment of laryngeal cancer

Introduction

Tumours connected with head and neck comprise about 5% of all tumours. The most frequent histological type of laryngeal carcinoma is squamous cell carcinoma. Different research projects suggest that the role of T lymphocytes might be significant in tumour development. iNKT cells are a new subpopulation of T cells and show cytotoxic activity against tumours. iNKT cells participate in modulating the function of other cells which have anti-tumour properties and secrete cytokines, which have pro-inflammatory and anti-inflammatory effects. In animal models the significance of iNKT cells in various diseases including cancer was shown.

Aim of the study

The aim of this study was to determine the percentages of iNKT cells, CD161+ cells, CD161– cells, iNKT CD4+ cells, and iNKT CD8+ cells, NK cells, NKT-like cells, and T cells subsets present in peripheral blood of patients with laryngeal cancer before and two months after the tumour resection, in comparison to healthy volunteers.

Materials and methods

This study included material from laryngeal patients who were treated at the Department of Otolaryngology and Laryngological Oncology (Medical University of Lublin) between 2012 and 2013. A total of 50 patients (40 men and 10 women) aged between 45 and 77 years (median age: 60 years) were enrolled. Based on the TNM classification, the patients were classified as having stage I-IV laryngeal cancer. The control group was composed of 15 healthy volunteers (12 men and three women) aged between 43 and 82 years (median age: 61 years). The protocol of the study was approved by the Local Bioethical Committee at the Medical University of Lublin.

Peripheral blood samples (15 ml) from the basilic vein were collected by venipuncture using sterile, sodium heparin-treated tubes (20 units per ml of blood) and used for cytometric analyses.

Results

iNKT cells were analysed among T CD3+ cells. The percentage of CD3+ and CD3+CD4+ T cells before tumour resection was higher than in the control group, but the increase of CD3+ T cells was not significant. The T CD3+CD4+ / T CD3+CD8+ cell ratio was significantly higher than in healthy donors. After tumour resection a decreased percentage of CD3+CD4+ T cells but an increased percentage of CD8+CD3+T cells was noted. The T CD3+CD4+ / T CD3+CD8+ cell ratio was significantly higher in patients before and after the surgery than in the control group. The amount of NKT-like cells increased after resection and was significantly higher than in the control group.

Conclusions

Our study exhibited the change in percentage of iNKT, NK, NKT-like cells, and T lymphocytes after tumour resection in patients with laryngeal cancer. The research explains the contribution of those cells in immunological response against tumour.

Invariant NKT cells increase drug-induced osteosarcoma cell death

BACKGROUND AND PURPOSE

In osteosarcoma (OS) patients, only a limited number of drugs are active and the regimens currently in use include a combination of at least two of these drugs: doxorubicin, cisplatin, methotrexate and ifosfamide. Today, 30-40% of patients still die of OS highlighting the urgent need for new treatments. Invariant NKT (iNKT) cells are a lymphocyte lineage with features of both T and NK cells, playing important roles in tumour suppression. Our aim was to test whether the cytoxicity induced by cisplatin, doxorubicin and methotrexate against OS cells can be enhanced by iNKT cell treatment.

EXPERIMENTAL APPROACH

iNKT cells were purified from human peripheral blood mononuclear cells by cell sorting (Vα24Vβ11(+) cells) and used as effector cells against OS cells (U2-OS, HOS, MG-63). Cell death (calcein-AM method), perforin/granzyme B and Fas/FasL expressions were determined by flow cytometry. CD1d expression was analysed at both the gene and protein level.

KEY RESULTS

iNKT cells were cytotoxic against OS cells through a CD1d-dependent mechanism. This activity was specific for tumour cells, because human CD1d(+) mesenchymal stem cells and CD1d(-) osteoblasts were not affected. iNKT cell treatment enhanced drug-induced OS cell death in a concentration-dependent manner and this effect was reduced in CD1d-silenced OS cells.

CONCLUSION AND IMPLICATIONS

iNKT cells kill malignant, but not non-malignant, cells. iNKT cell treatment enhances the cytotoxicity of anti-neoplastic drugs against OS cells in a CD1d-dependent manner. The present data encourage further studies on the use of iNKT cells in OS therapy.

Increased frequency of circulating invariant natural killer T cells in malignant pleural mesothelioma patients

Invariant natural killer T (iNKT) cells are a distinct subset of human T cells, which expresses an invariant T cell receptor Vα24 Jα18 and recognizes glycolipid antigens in the context of CD1d molecules. iNKT cells exert pivotal regulatory roles in many immune responses, including antitumor immune responses. Alterations in iNKT cell frequency, phenotype, and activation state have been reported in cancer patients. No data are available on the iNKT cells in malignant pleural mesothelioma (MPM), a rare, but very aggressive, malignancy of the pleura with a very poor prognosis. Here, we studied the frequency, phenotype, and cytokine profile of circulating iNKT cells in MPM patients, and correlated results with tumor histological types (epithelioid, sarcomatoid, biphasic) and clinical stages (I-III). We found that the iNKT cell frequency was significantly increased in MPM patients with epithelioid and sarcomatoid types in comparison with healthy volunteers (HV); only three biphasic mesotheliomas were available in this study, thus no conclusions can be drawn for this MPM type. The increased frequency significantly correlates with the clinical stage of tumor with the highest value at the stage III in both epithelioid and sarcomatoid subtypes. According to the histological types, we measured changes in the frequencies of CD4⁺ CD8⁺ (DP) and CD4⁻CD8⁻ (DN), but not in the cytokine profiles (IFN-γ/IL-4 expression). These results demonstrate that the frequency of iNKT cells is increased in MPM patients and that this increase correlates with MPM type and stage.

Altered peripheral invariant natural killer T cells in atopic dermatitis

BACKGROUND

Conflicting data exist on the number of invariant NKT (iNKT) cells in atopic dermatitis (AD); furthermore, no data have been published on their functional capacity.

METHODS

The frequency and number of circulating CD3+6B11+ iNKT cells and their CD4+ and CD4- subpopulations were evaluated in peripheral blood obtained from 41 patients with AD by four-color flow cytometry. Likewise, functional properties of iNKT cells were measured by five-color intracellular cytokine staining.

RESULTS

The number and percentage of total iNKT cells and their CD4/CD8 subpopulations were significantly lower than the controls. Of further importance, the CD4-CD8- (double negative, DN) iNKT subgroup showed the strongest positive correlation with total iNKT cells. In addition, the DN subgroup exhibited the most pronounced functional alteration with significantly decreased levels of intracellular IFNγ and significantly increased levels of intracellular IL-4 in AD patients compared with the controls.

CONCLUSION

The significantly altered number and cytokine production of iNKT cells from AD patients suggests that these cells may play an important role in the pathogenesis of AD.

Isolation and functional use of human NKT cells

This unit details methods for the isolation, in vitro expansion, and functional characterization of human iNKT cells. The term iNKT derives from the fact that a large fraction of murine NKT cells recognize the MHC class I-like CD1d protein, are CD4+ or CD4-CD8- (double negative), and use an identical "invariant" TCRalpha chain, which is generated by precise Valpha14 and Jalpha281 (now renamed Jalpha18) rearrangements with either no N-region diversity or subsequent trimming to nearly identical amino-acid sequence (hence, 'iNKT'). Basic Protocol 1 and Alternate Protocol 1 use multi-color FACS analysis to identify and quantitate rare iNKT cells from human samples. Basic Protocol 2 describes iNKT cell purification. Alternate Protocol 2 describes a method for high-speed FACS sorting of iNKT cells. Alternate Protocol 3 employs a cell sorting approach to isolate iNKT cell clones. A Support Protocol for secondary stimulation and rapid expansion of iNKT cells is also included. Basic Protocol 3 explains functional analysis of iNKT.

Development and application of a multiplexable flow cytometry-based assay to quantify cell-mediated cytolysis

Although target cell cytolysis has been widely employed to describe effector function of cells, cytolysis assays as commonly employed do not generate quantitative data. In this report we describe the development and application of a statistically supported flow cytometry-based assay to quantify cell-mediated cytolysis. The assay depends on the use of the fluorescent dye CFSE to distinguish target from effector cells, the DNA intercalating dye 7AAD to distinguish dead from live cell events, and on the establishment of a cytolysis curve that allows for the derivation of statistically robust data. We demonstrate that the cytolysis curve is well described by a four parameter logistic regression model provided that (i) the range of effector to target (E:T) ratios studied allows for full description of the logistic curve, and (ii) an adequate number of data points are collected to estimate the model parameters. We show that the assay is highly reproducible and accurate, and comparable in sensitivity with the standard (51)Cr assay. We report on the potential for this assay to generate quantitative data on the cytolytic activity of both CD8 T and NK cells; describe a relationship between the efficiency of effector cell degranulation and target cell cytolysis throughout a range of E:T ratios, and demonstrate the potential to multiplex with other platforms to obtain broader datasets for the effector phenotype of cells. Appropriate use of this assay will enhance the ability to derive quantitative and integrated correlative datasets from basic, translational, and clinical studies.

Thymic stromal lymphopoietin-activated invariant natural killer T cells trigger an innate allergic immune response in atopic dermatitis

BACKGROUND

Although invariant natural killer T (iNKT) cells have been shown to play a critical role in the pathogenesis of asthma, the role of iNKT cells in atopic dermatitis (AD) has not been well evaluated.

OBJECTIVE

We investigated whether iNKT cells in patients with AD increased and whether iNKT cells were activated by thymic stromal lymphopoietin (TSLP), which is highly expressed in keratinocytes of AD.

METHODS

We assessed the population of iNKT cells in PBMCs of patients with AD and healthy controls (HCs) using flow cytometry. Immunohistochemistry was used to evaluate iNKT cells and TSLP expression in AD and HC skin. We also evaluated whether iNKT cells expressed the TSLP receptor, the effects of TSLP on iNKT cells, and iNKT cell-dendritic cell interactions in a TSLP-rich environment.

RESULTS

There were more iNKT cells among PBMCs of patients with moderate to severe AD than mild AD (P < .05) and HC (P < .001). The number of iNKT cells was significantly larger in severe AD skin lesions than in mild (P < .001) or moderate AD skin lesions (P < .05). TSLP expression increased in lesional skin (P < .001) but not in the sera of patients with AD (P = .729) compared with HC. iNKT cells expressed TSLP receptor protein and mRNA. TSLP directly activated iNKT cells to secrete IL-4 and IL-13, and the concurrent addition of dendritic cells further activated IFN-gamma expression.

CONCLUSION

Increased iNKT cells activated by TSLP, especially in patients with severe AD, might play an essential role in the innate allergic immune response in AD.

Novel cancer vaccine based on genes of Salmonella pathogenicity island 2

Although tumors express potentially immunogenic tumor-associated antigens (TAAs), cancer vaccines often fail because of inadequate antigen delivery and/or insufficient activation of innate immunity. Engineering nonpathogenic bacterial vectors to deliver TAAs of choice may provide an efficient way of presenting TAAs in an immunogenic form. In this study, we used genes of Salmonella pathogenicity island 2 (SPI2) to construct a novel cancer vaccine in which a TAA, survivin, was fused to SseF effector protein and placed under control of SsrB, the central regulator of SPI2 gene expression. This construct uses the type III secretion system (T3SS) of Salmonella and allows preferential delivery of tumor antigen into the cytosol of antigen-presenting cells for optimal immunogenicity. In a screen of a panel of attenuated strains of Salmonella, we found that a double attenuated strain of Salmonella typhimurium, MvP728 (purD/htrA), was not toxic to mice and effectively expressed and translocated survivin protein inside the cytosol of murine macrophages. We also found that a ligand for CD1d-reactive natural killer T (NKT) cells, alpha-glucuronosylceramide (GSL1), enhanced MvP728-induced interleukin-12 production in human dendritic cells and that in vivo coadministration of a NKT ligand with MvP728-Llo or MvP728-survivin enhanced effector-memory cytotoxic T lymphocyte (CTL) responses. Furthermore, combined use of MvP728-survivin with GSL1 produced antitumor activity in mouse models of CT26 colon carcinoma and orthotopic DBT glioblastoma. Therefore, the use of TAA delivery via SPI-2-regulated T3SS of Salmonella and NKT ligands as adjuvants may provide a foundation for new cancer vaccines.

Valpha24-invariant NKT cells mediate antitumor activity via killing of tumor-associated macrophages

Tumor infiltration with Valpha24-invariant NKT cells (NKTs) associates with favorable outcome in neuroblastoma and other cancers. Although NKTs can be directly cytotoxic against CD1d+ cells, the majority of human tumors are CD1d-. Therefore, the role of NKTs in cancer remains largely unknown. Here, we demonstrate that CD68+ tumor-associated monocytes/macrophages (TAMs) represented the majority of CD1d-expressing cells in primary human neuroblastomas. TAMs stimulated neuroblastoma growth in human cell lines and their xenografts in NOD/SCID mice via IL-6 production. Indeed, TAMs produced IL-6 in primary tumors and in the BM of patients with metastatic neuroblastoma. Gene expression analysis using TaqMan low-density arrays of 129 primary human neuroblastomas without MYCN amplification revealed that high-level expression of TAM-specific genes (CD14, CD16, IL6, IL6R, and TGFB1) was associated with poor 5-year event-free survival. While NKTs were not cytotoxic against neuroblastoma cells, they effectively killed monocytes pulsed with tumor cell lysate. The killing of monocytes was CD1d restricted because it was inhibited by a CD1d-specific mAb. Cotransfer of human monocytes and NKTs to tumor-bearing NOD/SCID mice decreased monocyte number at the tumor site and suppressed tumor growth compared with mice transferred with monocytes alone. Thus, killing of TAMs reveals what we believe to be a novel mechanism of NKT antitumor activity that relates to the disease outcome.

Effect of allergen challenge on the percentage of natural killer T cells in patients with atopic asthma

BACKGROUND

Invariant natural killer T (iNKT) cells produce cytokines that can influence the immune response to infection or allergen. Controversy surrounds their role in exacerbations of human atopic asthma.

OBJECTIVES

To determine the effect of allergen challenge on iNKT cells' mobilization to the airways and blood and to establish the relationship between airway iNKT cells and bronchial sensitivity to methacholine and allergen in patients with atopic asthma.

METHODS

We performed flow cytometry analysis for the iNKT cell receptor Va24 and V311 on bronchoalveolar lavage (BAL) cells at baseline and 24 hours after segmental antigen challenge (SAC) (n = 8) and on peripheral blood mononuclear cells (PBMCs) at baseline and 6 to 7 hours after inhaled allergen (n = 10). Challenges were performed using standardized protein allergens to which the participants were sensitive.

RESULTS

The number of BAL eosinophils increased 24 hours after SAC. The low mean (SEM) baseline percentage of iNKT cells in the population of BAL CD4' T cells remained unchanged 24 hours after SAC (0.035% [0.01%] vs 0.049% [0.02%]; n = 8; P = .50). Likewise, the mean (SEM) percentage of iNKT cells in PBMCs was unchanged after inhaled allergen provocation (0.068% [0.033%] vs 0.057% [0.026%]; n = 10; P = .10). No correlation was found between iNKT cells in BAL and the sensitivity to inhaled methacholine or allergen.

CONCLUSIONS

The percentages of both BAL and peripheral blood iNKT cells did not increase during allergen provoked asthmatic responses. Determination of iNKT cells in airway biopsy specimens would allow conclusively ruling against mobilization of iNKT cells in allergen-induced asthma exacerbation in humans.

Frequency and function of circulating invariant NKT cells in autoimmune diabetes mellitus and thyroid diseases in Colombian patients

The frequency and functionality of peripheral blood invariant (iNKT) cells and their subsets, as well as other regulatory T-cell subsets, were evaluated in patients with type 1A diabetes mellitus (DM1), Hashimoto's disease, and Graves' disease. In addition to healthy individuals (HC), patients with type 2 diabetes mellitus (DM2) were included as controls because this disease has a different physiopathology. A similar frequency of total iNKT cells, as well as their subsets, existed among HC and the different study groups. Similar results were reported when we compared the frequency of CD4(+)/CD25(high) T cells, CD8(+)/CD28(negative) T cells, and gamma-delta T cells among HC and study groups, whereas patients with DM2 exhibited a higher frequency of CD8(+)/CD28(negative) T cells compared with HC and DM1. Also, patients with DM2 exhibited a lower frequency of CD4(negative) and CD4(+) iNKT cells expressing tumor necrosis factor-alpha (TNF-alpha) than HC. We did not observe significant differences in the frequency of iNKT cells expressing interleukin-4 or interferon-gamma among study groups and controls. Our findings support a normal frequency and function of peripheral blood iNKT cells in different endocrine autoimmune diseases, but an abnormal expression of TNF-alpha by circulating iNKT cells from patients with DM2.

Identification of distinct human invariant natural killer T-cell response phenotypes to alpha-galactosylceramide

Background

Human CD1d-restricted, invariant natural killer T cells (iNKT) are a unique class of T lymphocytes that recognise glycolipid antigens such as α-galactosylceramide (αGalCer) and upon T cell receptor (TCR) activation produce both Th1 and Th2 cytokines. iNKT cells expand when cultured in-vitro with αGalCer and interleukin 2 (IL-2) in a CD1d-restricted manner. However, the expansion ratio of human iNKT cells varies between individuals and this has implications for attempts to manipulate this pathway therapeutically. We have studied a panel of twenty five healthy human donors to assess the variability in their in-vitro iNKT cell expansion responses to stimulation with CD1d ligands and investigated some of the factors that may influence this phenomenon.

Results

Although all donors had comparable numbers of circulating iNKT cells their growth rates in-vitro over 14 days in response to a range of CD1d ligands and IL-2 were highly donor-dependent. Two reproducible donor response patterns of iNKT expansion were seen which we have called 'strong' or 'poor' iNKT responders. Donor response phenotype did not correlate with age, gender, frequency of circulating iNKT, or with the CD1d ligand utilised. Addition of exogenous recombinant human interleukin 4 (IL-4) to 'poor' responder donor cultures significantly increased their iNKT proliferative capacity, but not to levels equivalent to that of 'strong' responder donors. However in 'strong' responder donors, addition of IL-4 to their cultures did not significantly alter the frequency of iNKT cells in the expanded CD3⁺ population.

Conclusion

(i) in-vitro expansion of human iNKT cells in response to CD1d ligand activation is highly donor variable, (ii) two reproducible patterns of donor iNKT expansion were observed, which could be classified into 'strong' and 'poor' responder phenotypes, (iii) donor iNKT response phenotypes did not correlate with age, gender, frequency of circulating iNKT cells, or with the CD1d ligand utilised, (iv) addition of IL-4 to 'poor' but not 'strong' responder donor cultures significantly increased their in-vitro iNKT cell expansion to αGalCer.

Human natural killer T cells infiltrate into the skin at elicitation sites of allergic contact dermatitis

The purpose of this study is to identify invariant natural killer T cells (NKT cells) in cellular infiltrate of human allergic contact dermatitis (ACD) skin challenge sites. Skin biopsy specimens were taken from positive patch test reactions from 10 different patients (9 different allergens) and studied by immunochemistry, real-time PCR, nested PCR, and in situ hybridization to identify NKT cells and the cytokines associated with this cell type. Invariant NKT cells were identified in all the 10 skin biopsy specimens studied, ranging from 1.72 to 33% of the cellular infiltrate. These NKT cells were activated in all cases, as they expressed cytokine transcripts for IFN-gamma and IL-4. Invariant NKT cells are present in ACD, regardless of the allergen that triggers the reaction, and are in an activated state. We conclude that innate immunity plays a role in late phases of type IV hypersensitivity reactions and may be responding to self-lipids released during allergic inflammation. These data complement the previous work by other investigators that suggest that NKT cells are important in the early cellular response during primary immune responses to allergens. Herein, it is demonstrated that NKT cells are constantly present during the late elicitation phase of human type IV hypersensitivity reactions.

Oncogene MYCN regulates localization of NKT cells to the site of disease in neuroblastoma

Valpha24-invariant natural killer T (NKT) cells are potentially important for antitumor immunity. We and others have previously demonstrated positive associations between NKT cell presence in primary tumors and long-term survival in distinct human cancers. However, the mechanism by which aggressive tumors avoid infiltration with NKT and other T cells remains poorly understood. Here, we report that the v-myc myelocytomatosis viral related oncogene, neuroblastoma derived (MYCN), the hallmark of aggressive neuroblastoma, repressed expression of monocyte chemoattractant protein-1/CC chemokine ligand 2 (MCP-1/CCL2), a chemokine required for NKT cell chemoattraction. MYCN knockdown in MYCN-amplified neuroblastoma cell lines restored CCL2 production and NKT cell chemoattraction. Unlike other oncogenes, MYCN repressed chemokine expression in a STAT3-independent manner, requiring an E-box element in the CCL2 promoter to mediate transcriptional repression. MYCN overexpression in neuroblastoma xenografts in NOD/SCID mice severely inhibited their ability to attract human NKT cells, T cells, and monocytes. Patients with MYCN-amplified neuroblastoma metastatic to bone marrow had 4-fold fewer NKT cells in their bone marrow than did their nonamplified counterparts, indicating that the MYCN-mediated immune escape mechanism, which we believe to be novel, is operative in metastatic cancer and should be considered in tumor immunobiology and for the development of new therapeutic strategies.

Expansion of Pulmonary CD8+CD56+ Natural Killer T-Cells in Hypersensitivity Pneumonitis

BACKGROUND

Natural killer T (NKT) cells, a newly identified subgroup of T cells with immunoregulatory function, may be implicated in the pathogenesis of interstitial lung disease (ILD).

METHODS

We used multiparameter flow cytometry with antibodies to CD3, CD4, CD8, CD14, CD19, CD45, CD16/56, CD56, CD161, and Valpha24 invariant T-cell receptor (TCR) in BAL fluid (BALF) to examine the frequency and distribution of pulmonary NKT cells in several cases of ILD. We included 57 patients with sarcoidosis and 17 patients with hypersensitivity pneumonitis.

RESULTS

We found significantly higher frequencies of pulmonary NKT cells in patients with hypersensitivity pneumonitis in comparison to the other study patients with ILD (median proportion of NKT cells, 11%; range, 3 to 38%; vs 3%; range, 0 to 16%; p < 0.0001). In contrast, there was no difference in the proportion of conventional natural killer cells. We found that a major subset of NKT cells in the BALF of patients with hypersensitivity pneumonitis was a CD8+CD56+ population that did not express the invariant TCR.

CONCLUSIONS

These results suggest the involvement of NKT cells in the pathogenesis of hypersensitivity pneumonitis.

Association of the frequency of peripheral natural killer T cells with nonalcoholic fatty liver disease

AIM: To investigate whether changes in the frequency of peripheral natural killer T (NKT) cells were correlated with liver disease in patients who had metabolic predispositions to nonalcoholic fatty liver disease (NAFLD).

METHODS: Peripheral blood samples were obtained from 60 Chinese NAFLD patients and 60 age and gender matched healthy controls. The frequency of peripheral NKT cells was detected by flow cytometry. Clinical and laboratory data were collected for further analysis.

RESULTS: NAFLD patients had a lower frequency of peripheral NKT cells than healthy controls (1.21% ± 0.06% vs 1.62% ± 0.07%, P < 0.001). Further analysis revealed that the frequency of peripheral NKT cells was negatively correlated with body mass index, waist circumference and serum levels of alanine aminotransferase. Logistic regression analysis revealed that elevated body mass index [hazard ratio (HR): 2.991], aspartate aminotransferase levels (HR: 1.148) and fasting blood sugar (HR: 3.133) increased the risk of NAFLD, whereas an elevated frequency of peripheral NKT cells (HR: 0.107) decreased the risk.

CONCLUSION: Changes in the frequency of peripheral NKT cells were correlated with NAFLD and a decreased frequency of peripheral NKT cells was a risk factor for NAFLD.

Characterization of human invariant natural killer T subsets in health and disease using a novel invariant natural killer T cell-clonotypic monoclonal antibody, 6B11

Identification of human CD1d-restricted T-cell receptor (TCR)-invariant natural killer T (iNKT) cells has been dependent on utilizing combinations of monoclonal antibodies or CD1d tetramers, which do not allow for the most specific analysis of this T-cell subpopulation. A novel monoclonal antibody (clone 6B11), specific for the invariant CDR3 loop of human canonical Valpha24Jalpha18 TCR alpha chain, was developed and used to specifically characterize iNKT cells. In healthy individuals studied for up to 1 year, a wide but stable frequency of circulating iNKT cells (range: 0.01-0.92%) was observed, with no differences in frequency by gender. Four stable iNKT cell subsets were characterized in peripheral blood based on the expression of CD4 and CD8, with CD8(+) iNKT cells being a phenotypic and functionally different subset from CD4(+) and double negative iNKT cells; in particular, LAG-3 was preferentially expressed on CD8(+) iNKT cells. In addition, a strong negative linear correlation between the frequency of total iNKT cells and percentage of the CD4(+) subset was observed. In terms of their potential association with disease, patients at risk for type 1 diabetes had significantly expanded frequencies of double negative iNKT cells when compared to matched controls and first-degree relatives. Moreover, peripheral blood CD4(+) iNKT cells were the highest producers of interleukin-4, while the production of interferon-gamma and tumour necrosis factor-alpha was similar amongst all iNKT cell subsets. These differences in iNKT cell subsets suggest that in humans the relative ratio of iNKT cell subsets may influence susceptibility vs. resistance to immune-mediated diseases.

Invariant natural killer T cells in asthma and chronic obstructive pulmonary disease

BACKGROUND

The number of type 2 helper CD4+ T cells is increased in the airways of persons with asthma. Whether the majority of these cells are class II major-histocompatibility-complex-restricted cells or are among the recently identified CD1d-restricted invariant natural killer T cells is a matter of controversy. We studied the frequency of invariant natural killer T cells in the airways of subjects with mild or moderately severe asthma to investigate the possibility of an association between the number of invariant natural killer T cells in the airway and disease severity. We also studied whether an increased number of these cells is a feature of chronic obstructive pulmonary disease (COPD).

METHODS

We enumerated invariant natural killer T cells by flow cytometry with the use of CD1d tetramers loaded with alpha-galactosylceramide and antibodies specific to the invariant natural killer T-cell receptor in samples of bronchoalveolar-lavage fluid, induced sputum, and bronchial-biopsy specimens obtained from subjects with mild or moderately severe asthma, subjects with COPD, and healthy control subjects. Real-time polymerase-chain-reaction analysis was performed on bronchoalveolar-lavage cells for evidence of gene expression of the invariant natural killer T-cell receptor.

RESULTS

Fewer than 2% of the T cells obtained from all subjects on airway biopsy, bronchoalveolar lavage, and sputum induction were invariant natural killer T cells, with no significant differences among the three groups of subjects. No expression of messenger RNA for the invariant natural killer T-cell-receptor domains Valpha24 and Vbeta11 was detected in bronchoalveolar-lavage cells from subjects with asthma.

CONCLUSIONS

Invariant natural killer T cells are found in low numbers in the airways of subjects with asthma, subjects with COPD, and controls.

A high-throughput method for detection of DNA in chloroplasts using flow cytometry

BACKGROUND

The amount of DNA in the chloroplasts of some plant species has been shown recently to decline dramatically during leaf development. A high-throughput method of DNA detection in chloroplasts is now needed in order to facilitate the further investigation of this process using large numbers of tissue samples.

RESULTS

The DNA-binding fluorophores 4',6-diamidino-2-phenylindole (DAPI), SYBR Green I (SG), SYTO 42, and SYTO 45 were assessed for their utility in flow cytometric analysis of DNA in Arabidopsis chloroplasts. Fluorescence microscopy and real-time quantitative PCR (qPCR) were used to validate flow cytometry data. We found neither DAPI nor SYTO 45 suitable for flow cytometric analysis of chloroplast DNA (cpDNA) content, but did find changes in cpDNA content during development by flow cytometry using SG and SYTO 42. The latter dye provided more sensitive detection, and the results were similar to those from the fluorescence microscopic analysis. Differences in SYTO 42 fluorescence were found to correlate with differences in cpDNA content as determined by qPCR using three primer sets widely spaced across the chloroplast genome, suggesting that the whole genome undergoes copy number reduction during development, rather than selective reduction/degradation of subgenomic regions.

CONCLUSION

Flow cytometric analysis of chloroplasts stained with SYTO 42 is a high-throughput method suitable for determining changes in cpDNA content during development and for sorting chloroplasts on the basis of DNA content.

Synthesis and evaluation of an alpha-C-galactosylceramide analogue that induces Th1-biased responses in human natural killer T cells

An alpha-galactosylceramide (alphaGalCer, 1) and its isosteric C-glycoside analogue (2) were found to possess promising immunostimulatory activity because of their ability to activate natural killer T (NKT) cells. We report the synthesis of compound 3, a truncated nonisosteric C-alphaGalCer analogue, that like 2 is not enzymatically labile at the glycosidic linkage, but has the anomeric carbon directly bonded to the C1 of the phytoceramide backbone. We compared the biological activity of the three ligands using an in vitro system with human dendritic cells as the antigen-presenting cells and human NKT cells as the responding cells. Although 3 was a less potent agonist for NKT cells than 1 and 2, it induced cytokine production with the highest IFN-gamma:IL-4 and IFN-gamma:IL-13 ratios. Therefore, our data suggest that the new mimetic of alphaGalCer might preferentially promote Th1-immune responses and serve as a potent adjuvant in the immunotherapy of cancer and infectious diseases.

Increased Frequency of CD4+ Cells Expressing CD161 in Cancer Patients

PURPOSE

Although the function of natural killer receptors on T cells infiltrating tumors and their potential effect on antitumor immunity has been investigated, little is known about T cells expressing NKR-P1A (CD161) in cancer patients. In the present study, we examined T cells expressing CD161 in the peripheral blood, the tumor tissue and in malignant effusions of patients with several types of malignancies.

EXPERIMENTAL DESIGN

Expression of CD161 in CD4(+) or CD8(+) (lacking CD56) T cells isolated from peripheral blood (n = 61), tumor specimens (n = 8), and malignant effusions (n = 37) of cancer patients was examined using four-color flow cytometry. Proliferative capacity and cytokine production of purified CD4(+)CD161(+)CD56(-) cells were studied after weak or strong stimulation, with or without costimulation, in the presence or absence of interleukin 2. The possible regulatory function of activated CD4(+)CD161(+)CD56(-) cells on T-cell alloresponses was also investigated.

RESULTS

CD4(+) cells expressing CD161 were increased in cancer patients, compared with healthy individuals. This increase in the peripheral blood of cancer patients positively correlated with disease stage and was augmented at the tumor site. Phenotypic analysis revealed that CD4(+)CD161(+) cells are memory T cells, with low expression of activation markers. CD4(+)CD161(+) cells play an immunoregulatory role through cytokine production, because upon receiving costimulatory signals via CD28, they exert suppressive activity on autologous peripheral blood mononuclear cell alloresponses.

CONCLUSIONS

CD4(+)CD161(+)CD56(-) cells represent a distinct memory T-cell population significantly increased in cancer patients. Depending on the type of signals provided by the tumor microenvironment, CD4(+)CD161(+) cells may regulate the immune response.

Implementation of the EGFP-K562 flow cytometric NK test: Determination of NK cytotoxic activity in healthy elderly volunteers before and after feeding

BACKGROUND

Natural Killer (NK) cells are key actors of innate immunity that supervise the organism's cells, and fight against viral infections and cancer development through their cytotoxic activity. This cytotoxic activity is modulated by cytokines and hormones and could be influenced by physiological or pathological conditions. New techniques for measuring NK cytotoxic activity by flow-cytometry have recently been developed, and they correlated strongly with the standard chromium ((51)Cr) release assay. Our aim was to implement a previously published enhanced green fluorescent protein (EGFP)-K562 flow cytometric method and use it to evaluate NK cytotoxic activity under different nutritional conditions.

METHODS

NK effector cells were isolated from peripheral blood mononuclear cells, and a K562 cell line stably transfected by EGFP was used as target cells. Different analytical parameters, including cell ratios and incubation times, were studied to improve the EGFP-K562 flow cytometric NK test conditions.

RESULTS

The optimized test was then used to determine the effect of fasting and refeeding on NK cell numbers and activity in a physiological situation. NK cytotoxic activity in fasted conditions (30.4 +/- 4.4%) increased by a factor 1.7 +/- 0.2 (P = 0.0025) in nourished conditions (45.0 +/- 4.6%) in healthy elderly people.

CONCLUSION

Therefore, this method provides a reliable, reproducible and rapid test for analyzing NK cytotoxicity under various conditions.

Granulysin, a Cytolytic Molecule, Is Also a Chemoattractant and Proinflammatory Activator

Granulysin, a cationic protein produced by activated human CTL and NK cells, is cytolytic against microbial and tumor targets. In this study we show that granulysin also functions as a chemoattractant and activates monocytes to produce cytokines/chemokines. Although granulysin-mediated cytotoxicity occurs at micromolar concentrations, chemoattraction occurs in the nanomolar range, and immune activation occurs over a wide range of concentrations (nanomolar to micromolar). Granulysin causes a 2- to 7-fold increase in chemotaxis of monocytes, CD4(+), and CD8(+) memory (CD45RO) but not naive (CD45RA) T cells, NK cells, and mature, but not immature, monocyte-derived dendritic cells. Pertussis toxin treatment abrogates chemoattraction by granulysin, indicating involvement of G-protein-coupled receptor(s). At low concentrations (10 nM), granulysin promotes a 3- to 10-fold increase in MCP-1 and RANTES produced by monocytes and U937 cells, while a 2-fold increase in TNF-alpha production by LPS-stimulated monocytes requires higher concentrations of granulysin (micromolar). Taken together, these data indicate that the local concentration of granulysin is critical for the biologic activity, with high concentrations resulting in cytotoxicity while lower concentrations, presumably further from the site of granulysin release, actively recruit immune cells to sites of inflammation.