Differentiation of human alloreactive CD8(+) T cells in vitro

Exosomal O-GlcNAc transferase from esophageal carcinoma stem cell promotes cancer immunosuppression through up-regulation of PD-1 in CD8+ T cells

Esophageal carcinoma stem cells (ECSCs) are responsible for the initiation and therapy-resistance of esophageal cancer. Nutrient sensor O-GlcNAc transferase (OGT) promoted the growth and metastasis of cancer cells. However, the contributions of OGT to the tumorigenesis of ECSCs remain largely uncover. In the present study, as compared to matched non-stem cancer cells, the expression of OGT was higher in ALDH⁺ ECSCs. Knock down of OGT by lentivirus system reduced the self-renewal capacities and tumorigenicity of ALDH⁺ ECSCs. In addition, OGT in exosome derived from ALDH⁺ ECSCs was taken up by neighboring CD8⁺ T cells and increased the expression of PD-1 in CD8⁺ T cells. Down-regulation of OGT increased the apoptosis of ALDH⁺ ECSCs induced by CD8⁺ T cells, which could be blocked by overexpression of PD-1 in CD8⁺ T cells. Together, OGT in exosome from ECSCs protects ECSCs from CD8⁺ T cells through up-regulation of PD-1.

Effect of asbestos exposure on differentiation and function of cytotoxic T lymphocytes

Asbestos exposure is known to cause malignant mesothelioma, which is associated with poor prognosis. We focused on and examined the effect of asbestos exposure on the differentiation and function of cytotoxic T lymphocytes (CTLs). CTLs have the ability to specifically attack tumor cells after being differentiated from naïve CD8⁺ T cells following antigen stimulation. Exposure to chrysotile B asbestos suppressed the differentiation of CTLs during the mixed lymphocyte reaction (MLR) and was associated with a decrease in proliferation of CD8⁺ T cells. Additionally, in an effort to investigate the mechanism associated with suppressed CTL differentiation upon exposure to asbestos, we focused on IL-2, a cytokine involved in T cell proliferation. Our findings indicated that insufficient levels of IL-2 are not the main cause for the suppressed induction of CTLs by asbestos exposure, although they suggest potential improvement in the suppressed CTL function. Furthermore, the functional properties of peripheral blood CD8⁺ lymphocytes from asbestos-exposed individuals with pleural plaque (PP) and patients with malignant mesothelioma (MM) were examined. MM patients showed lower perforin levels in CD8⁺ lymphocytes following stimulation compared with PP-positive individuals. The production capacity of IFN-γ in the MM group tended to be lower compared with healthy volunteers or PP-positive individuals. In an effort to determine whether chronic and direct asbestos exposure affected the function of CD8⁺ T cells, cultured human CD8⁺ T cells were employed as an in vitro model and subjected to long-term exposure to chrysotile (CH) asbestos. This resulted in decreased levels of intracellular perforin and secreted IFN-γ. Those findings underlie the possibility that impaired CD8⁺ lymphocyte function is caused by asbestos exposure, which fail to suppress the development of MM. Our studies therefore reveal novel effects of asbestos exposure on CTLs, which might contribute towards the development and implementation of an effective strategy for the prevention and cure of malignant mesothelioma.

Antigen-specific CD8+ T cell feedback activates NLRP3 inflammasome in antigen-presenting cells through perforin

The connection between innate and adaptive immunity is best exemplified by antigen presentation. Although antigen-presenting cells (APCs) are required for antigen receptor-mediated T-cell activation, how T-cells feedback to APCs to sustain an antigen-specific immune response is not completely clear. Here we show that CD8⁺ T-cell (also called cytotoxic T lymphocytes, CTL) feedback activates the NLRP3 inflammasome in APCs in an antigen-dependent manner to promote IL-1β maturation. Perforin from antigen-specific CTLs is required for NLRP3 inflammasome activation in APCs. Furthermore, such activation of NLRP3 inflammasome contributes to the induction of antigen-specific antitumour immunity and pathogenesis of graft-versus-host diseases. Our study reveals a positive feedback loop between antigen-specific CTLs and APC to amplify adaptive immunity.

Activation-induced CD137 is a fast assay for identification and multi-parameter flow cytometric analysis of alloreactive T cells

Detection and isolation of viable alloreactive T cells at the single-cell level requires a cell surface marker induced specifically upon T cell receptor activation. In this study, a member of the tumour necrosis factor receptor (TNFR)-family, CD137 (4-1BB) was investigated for its potential to identify the total pool of circulating alloreactive T cells. Optimal conditions for sensitive and specific detection of allogeneic-induced CD137 expression on circulating T cells were established. Thereafter, CD137(+) alloreactive T cells were phenotypically and functionally characterized by multi-parameter flow cytometry. Alloantigen-induced CD137 expression identified both alloreactive CD8(+) T cells (mean ± standard error of the mean: 0·21 ± 0·07%) and alloreactive CD4(+) T cells (0·21 ± 0·05%). CD137(+) alloreactive T cells were detected in different T cell subsets, including naive T cells, but were found preferentially in CD28(+) T cells and not in the terminally differentiated T cell subset. Upon allogeneic (re-)stimulation, the cytokine-producing as well as proliferative capacity of T cells resided mainly within the CD137-expressing fraction. About 10% of the CD137(+) alloreactive T cells produced any combination of interferon (IFN)-γ, interleukin (IL)-2 and TNF-α. Polyfunctional alloreactive T cells, defined by multiple cytokine expression, were observed infrequently. In conclusion, activation-induced CD137 expression is a fast assay allowing for detection and functional analysis of the total alloreactive T cell compartment at the single-cell level by multi-parameter flow cytometry.

Effect of asbestos exposure on differentiation of cytotoxic T lymphocytes in mixed lymphocyte reaction of human peripheral blood mononuclear cells

Asbestos fibers are associated with tumorigenicity, and are thought to cause mesothelioma. However, their effect on immune response remains unclear. We examined the effect of asbestos exposure on differentiation of cytotoxic T lymphocytes (CTLs) in mixed lymphocyte reactions (MLR) of human peripheral blood mononuclear cells (PBMCs) upon exposure to chrysotile B (CB) or crocidolite (CR) asbestos at 5 μg/ml for 7 days. Exposure to CB during MLR suppressed increases in the percentage and number of CD8⁺ T cells in response to allogenic cells. The cytotoxicity for allogenic targets decreased in PBMCs exposed to CB, but not CR, when compared with PBMCs without any exposure during MLR. Exposure to CB during MLR resulted in suppression of increases in granzyme B⁺ cells and IFN-γ⁺ cells. CB exposure also resulted in suppression of increases in CD45RO⁺ effector/memory cells and CD25⁺-activated cells in CD8⁺ lymphocytes, and a decrease in CD45RA⁺ cells. CB exposure suppressed the proliferation of CD8⁺ lymphocytes without an increase in annexin V⁺ apoptotic cells in CD8⁺ lymphocytes. Moreover, the production of IL-10, IFN-γ, and TNF-α, but not IL-2, decreased in the presence of CB. These results suggest that exposure to asbestos potentially suppresses the differentiation of cytotoxic T lymphocyte, accompanied by decreases in IFN-γ and TNF-α.

Selected allogeneic dendritic cells markedly enhance human tumour antigen-specific T cell response in vitro

BACKGROUND

Alloreaction is known to accumulate several theoretical advantages that can improve dendritic cell (DC)-based anti-infective or antitumour strategies. Allogeneic DC have already been tested in experimental and clinical studies, but their efficacy compared with their autologous counterparts was rarely investigated and conclusions diverge.

OBJECTIVE

This study compared antigen-specific T cell responses following priming with autologous versus allogeneic DC and examined the possibility of screening these responses in order to select allogeneic DC that lead to a great amplification.

RESULTS

Allogeneic DC obtained from donors matched with the single HLA-A2 allele were efficient in generating in vitro peptide-specific T cell responses. When randomly chosen, allogeneic DC generated a broad range of antigen-specific T cell responses in comparison with autologous DC. When screened and selected, allogeneic DC markedly enhanced peptide-specific T cell priming and allowed a more efficient boosting of resulting T cells. These selected allogeneic DC provided a favourable cytokinic and cellular environment that can help concurrent antigen-specific responses.

CONCLUSION

Ex vivo selected allogeneic DC provide adjuvant effects that lead to amplification of concomitant antigen-specific T cell responses.

The human alloreactive CD4+ T-cell repertoire is biased to a Th17 response and the frequency is inversely related to the number of HLA class II mismatches

Estimates of precursor frequency and assessment of functional characteristics of alloreactive CD4+ T cells are all biased by the need for long-term culture. In this study, direct visualization of human alloreactive CD4+ T cells on the single-cell level was achieved using cell surface expression of CD154 as a tool for identification. The average frequency of alloreactive CD154+CD4+ T cells among peripheral blood CD4+ T cells was 0.1%, with half of the cells displaying a naive phenotype. The proliferation capacity and expression of cytokines after allogeneic stimulation resided in these CD154+CD4+ T cells. The repertoire of alloreactive CD4+ T cells was biased to a Th17 response, and on average 24% of alloreactive CD154+CD4+ memory T cells produced interleukin-17 (IL-17) after polyclonal stimulation. Unexpectedly, mixed cell cultures from human leukocyte antigen (HLA)-identical donors also generated alloreactive CD154+CD4+ T cells and yielded the highest frequency compared with HLA-nonidentical combinations. Therefore, reactivity to minor histocompatibility antigens between HLA-identical subjects appears to be relatively common. Alloreactive HLA-identical T cells did not proliferate or express cytokines, but were driven to proliferation in the presence of exogenous IL-2.

Multiparameter Flow Cytometric Approach for Simultaneous Evaluation of Proliferation and Cytokine‐Secreting Activity in T Cells Responding to Allo‐stimulation

We report a method combining mixed lymphocyte reaction (MLR) using a carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeling technique, intracellular cytokine immunofluorescence staining (ICIS), and multiparameter flow cytometry for simultaneous determination of proliferation and cytokine-secreting activity in T cells responding to allo-stimulation. C57BL/6 (B6) mice and Balb/c mice were used in the experiments. CFSE-labeled responder splenocytes were cultured with irradiated stimulator splenocytes, followed by ICIS. In both the Balb/c stimulator-versus-B6 responder (Balb/c-vs.-B6) and the B6-vs.-Balb/c allogeneic combinations, interleukin (IL)-2 secreting cells and interferon (IFN)-gamma secreting cells were identified predominantly in proliferating CD4+ and CD8+ T cell fractions, respectively. The suitability of this method was proven by demonstrating a close relationship between the values of cytokines in culture supernatants (that were determined by Cytometric Bead Array assay) and indexes for cytokine-production (that were obtained by multiplying the percentage of cytokine-producing cells in T cells and mean fluorescence intensity of cytokine-staining determined by the combined MLR and ICIS).

Dynamics of the CD8 T-cell response following yellow fever virus 17D immunization

Management of yellow fever is focused on the prevention of illness by the use of the yellow fever virus (YFV) 17D vaccine. The role of neutralizing antibodies in protection is generally accepted with YFV-specific T cells likely contributing to the control of viral replication. We studied CD8(+) T-cell responses to four defined human leucocyte antigen-B35-restricted epitopes in YFV vaccine recipients as a model of the kinetics of cytotoxic T-lymphocyte responses to an acute human viral infection. Multiple features of these epitope-specific responses were analysed after vaccination including magnitude, cytokine production, phenotype and T-cell receptor repertoire. Peak peptide-specific interferon-gamma (IFN-gamma) responses of almost 1% of CD8(+) T cells were seen as early as 2 weeks post-vaccination; however, dominant responses varied between donors. Peptide-specific responses were still detectable at 54 months post-vaccination. Tetramer-positive cells, at high frequencies, were detected as early as 7-9 days, before detectable IFN-gamma-producing cells, suggesting a defect in the functional capacity of some antigen-specific cells early post-vaccination. The predominant memory phenotype of the tetramer-positive population was a differentiated effector (CD45RA(+) CCR7(-) CD62L(-)) phenotype. The T-cell receptor Vbeta analysis revealed a diverse oligoclonal repertoire in tetramer-positive T-cell populations in two individuals. These characteristics of the YFV-specific T-cell response could contribute to vaccine effectiveness.

CROSS-REACTIVITY OF CYTOMEGALOVIRUS-SPECIFIC CD8+ T CELLS TO ALLO-MAJOR HISTOCOMPATIBILITY COMPLEX CLASS I MOLECULES

BACKGROUND

In transplantation settings, cytomegalovirus (CMV) infection is a common complication. CMV infection is associated with a higher incidence of graft rejection in solid organ transplantation and graft-versus-host disease in bone marrow transplantation. The underlying mechanism of this association could be the generation of CMV-specific CD8 T cells capable of cross-reacting with alloantigens present on graft and host, respectively.

METHODS

Whereas as to date, no direct ex vivo analysis can be performed of the CD8 T-cell repertoire directed at allo-major histocompatibility complex (MHC) class I molecules, virus-specific cells can be readily enumerated by use of MHC-peptide tetrameric complexes. In this study, the authors used this technique to analyze potential overlapping CD8 T-cell repertoires between self-MHC-viral peptide and allo-MHC complexes by stimulating CMV-specific CD8 T cells with alloantigens. RESULTS.: The authors found that CMV-specific CD8 T cells are activated and proliferate on stimulation with alloantigens.

CONCLUSIONS

Although these cells are cytotoxic against CMV-peptide pulsed target cells, no cytotoxicity of CMV-specific cells to alloantigens could be detected, inferring that there are other mechanisms of graft damage by alloantigen-stimulated virus-specific CTL.