Byung-Seok Kim

IL-21-mediated reversal of NK cell exhaustion facilitates anti-tumour immunity in MHC class I-deficient tumours

During cancer immunoediting, loss of major histocompatibility complex class I (MHC-I) in neoplasm contributes to the evasion of tumours from host immune system. Recent studies have demonstrated that most natural killer (NK) cells that are found in advanced cancers are defective, releasing the malignant MHC-I-deficient tumours from NK-cell-dependent immune control. Here, we show that a natural killer T (NKT)-cell-ligand-loaded tumour-antigen expressing antigen-presenting cell (APC)-based vaccine effectively eradicates these advanced tumours. During this process, we find that the co-expression of Tim-3 and PD-1 marks functionally exhausted NK cells in advanced tumours and that MHC-I downregulation in tumours is closely associated with the induction of NK-cell exhaustion in both tumour-bearing mice and cancer patients. Furthermore, the recovery of NK-cell function by IL-21 is critical for the anti-tumour effects of the vaccine against advanced tumours. These results reveal the process involved in the induction of NK-cell dysfunction in advanced cancers and provide a guidance for the development of strategies for cancer immunotherapy.

Fibrinogen cleavage products and Toll-like receptor 4 promote the generation of programmed cell death 1 ligand 2–positive dendritic cells in allergic asthma

Background: Inhaled protease allergens preferentially trigger TH2‐mediated inflammation in allergic asthma. The role of dendritic cells (DCs) on induction of TH2 cell responses in allergic asthma has been well documented; however, the mechanism by which protease allergens induce TH2‐favorable DCs in the airway remains unclear. Objective: We sought to determine a subset of DCs responsible for TH2 cell responses in allergic asthma and the mechanism by which protease allergens induce the DC subset in the airway. Methods: Mice were challenged intranasally with protease allergens or fibrinogen cleavage products (FCPs) to induce allergic airway inflammation. DCs isolated from mediastinal lymph nodes were analyzed for surface phenotype and T‐cell stimulatory function. Anti‐Thy1.2 and Mas‐TRECK mice were used to deplete innate lymphoid cells and mast cells, respectively. Adoptive cell transfer, bone marrow DC culture, anti–IL‐13, and Toll‐like receptor (TLR) 4–deficient mice were used for further mechanistic studies. Results: Protease allergens induced a remarkable accumulation of TH2‐favorable programmed cell death 1 ligand 2 (PD‐L2)+ DCs in mediastinal lymph nodes, which was significantly abolished in mice depleted of mast cells and, to a lesser extent, innate lymphoid cells. Mechanistically, FCPs generated by protease allergens triggered IL‐13 production from wild‐type mast cells but not from TLR4‐deficient mast cells, which resulted in an increase in the number of PD‐L2+ DCs. Intranasal administration of FCPs induced an increase in numbers of PD‐L2+ DCs in the airway, which was significantly abolished in TLR4‐ and mast cell–deficient mice. Injection of IL‐13 restored the PD‐L2+ DC population in mice lacking mast cells. Conclusion: Our findings unveil the “protease–FCP–TLR4–mast cell–IL‐13” axis as a molecular mechanism for generation of TH2‐favorable PD‐L2+ DCs in allergic asthma and suggest that targeting the PD‐L2+ DC pathway might be effective in suppressing allergic T‐cell responses in the airway. Graphical abstract: Figure. No caption available.

IL21 Therapy Combined with PD-1 and Tim-3 Blockade Provides Enhanced NK Cell Antitumor Activity against MHC Class I–Deficient Tumors

Combination rIL21 and anti–PD-1/anti–Tim-3 additively enhanced NK cell responses in mice bearing MHCclass I–deficient tumors. This combination facilitated NK effector functions in cancer patients, highlighting its therapeutic potential for patients with MHC class I–deficient tumors. Increased expression of coinhibitory molecules such as PD-1 and Tim-3 on NK cells has been demonstrated in advanced cancer patients who harbor MHC class I–deficient tumors. However, even in preclinical models, the antitumor effects of checkpoint blockade on NK cells have not been clearly elucidated. Here, we show that anti–PD-1/anti–Tim-3 treatment suppressed tumor progression in mice bearing MHC class I–deficient tumors, and the suppression was further enhanced by recombinant IL21 (rIL21) treatments through an NK-cell–dependent mechanism. We also show that the intratumoral delivery of rIL21 attracted NK cells to the tumor site in a CXCR3-dependent fashion. A combination of IL21 and checkpoint blockade facilitated the effector function of exhausted NK cells in cancer patients. Given the effects of the checkpoint blockade and rIL21 combination on NK cells infiltrating into MHC class I–deficient tumors, we suggest that the efficacy of checkpoint blockade can be enhanced through the administration of IL21 for advanced cancer patients with MHC class I–low/deficient tumors. Cancer Immunol Res; 6(6); 685–95. ©2018 AACR.

Clonal Expansion of Allergen-specific CD4+ T Cell in the Lung in the Absence of Lymph Nodes

The expansion of allergen-specific CD4+ T cells is a critical step in inducing airway inflammation during allergic asthma. Such clonal expansion of T cells is initiated through the interaction between allergen-bearing dendritic cells and allergen-specific naïve T cells in the draining lymph nodes. Whether such T cell clonal expansion also occurs in the lung, the primary organ encountering inhaled allergens, remains unclear. Compared with wild-type mice, we found similar frequencies of CD4+ T cells in the lung of lymph node-deficient Rorgtgfp/gfp mice after repeated exposure to inhaled allergens. In addition, we observed an evident population of CD4+ T cells that underwent clonal expansion in the lung of allergen-challenged mice treated with an S1P antagonist FTY720 in an in vivo proliferation study with CFSE-labeled OT-II T cells. Moreover, the expansion of allergen-specific CD4+ T cells was significantly enhanced in the lungs of Rorgtgfp/gfp mice in comparison to that of wild-type mice. These results together demonstrate that the clonal expansion of allergen-specific CD4+ T cells occurs in the absence of the lymph nodes, indicating that the lung can act as a primary site of the clonal expansion of CD4+ T cells in response to inhaled allergens.

Activation of NKT Cells in an Anti-PD-1–Resistant Tumor Model Enhances Antitumor Immunity by Reinvigorating Exhausted CD8 T Cells

PD-1-based cancer immunotherapy is a successful example of immune checkpoint blockade that provides long-term durable therapeutic effects in patients with cancer across a wide spectrum of cancer types. Accumulating evidence suggests that anti-PD-1 therapy enhances antitumor immunity by reversing the function of exhausted T cells in the tumor environment. However, the responsiveness rate of patients with cancer to anti-PD-1 therapy remains low, providing an urgent need for optimization and improvement. In this study, we designed an anti-PD-1-resistant mouse tumor model and showed that unresponsiveness to anti-PD-1 is associated with a gradual increase in CD8 T-cell exhaustion. We also found that invariant natural killer T cell stimulation by the synthetic ligand α-galactosylceramide (αGC) can enhance the antitumor effect in anti-PD-1-resistant tumors by restoring the effector function of tumor antigen-specific exhausted CD8 T cells. IL2 and IL12 were among the cytokines produced by αGC stimulation critical for reinvigorating exhausted CD8 T cells in tumor-bearing mice and patients with cancer. Furthermore, we observed a synergistic increase in the antitumor effect between αGC-loaded antigen-presenting cells and PD-1 blockade in a therapeutic murine tumor model. Our study suggests NKT cell stimulation as a promising therapeutic strategy for the treatment of patients with anti-PD-1-resistant cancer.Significance: These findings provide mechanistic insights into the application of NKT cell stimulation as a potent adjuvant for immunotherapy against advanced cancer. Cancer Res; 78(18); 5315-26. ©2018 AACR.

Inhibition of autoimmune Th17 cell responses by pain killer ketamine

Ketamine is widely used in animals and humans as a systemic anesthetic. Although several immune-modulatory functions of ketamine have been reported, the effects of ketamine on the differentiation of Th17 cell are unknown. We found that ketamine significantly diminished the frequency of IL-17-producers among CD4+ T cells stimulated under Th17-skewing conditions. Mechanistic studies showed that ketamine had little effect on the production of Th17-inducing cytokines by dendritic cells and the proliferation of T cells in response to anti-CD3; however it significantly hampered IL-21 expression as well as STAT3 phosphorylation in T cells upon IL-6 stimulation. Moreover, MOG-reactive CD4+ T cells expanded in the presence of ketamine produced reduced amounts of Th17 cytokines, leading to diminished EAE severity when transferred into TCRβ-deficient mice in comparison to those treated with vehicle. These findings demonstrate that ketamine suppresses autoimmune Th17 cell responses by inhibiting the differentiation as well as the reactivation of Th17 cells.Ketamine is widely used in animals and humans as a systemic anesthetic. Although several immune-modulatory functions of ketamine have been reported, the effects of ketamine on the differentiation of Th17 cell are unknown. We found that ketamine significantly diminished the frequency of IL-17-producers among CD4+ T cells stimulated under Th17-skewing conditions. Mechanistic studies showed that ketamine had little effect on the production of Th17-inducing cytokines by dendritic cells and the proliferation of T cells in response to anti-CD3; however it significantly hampered IL-21 expression as well as STAT3 phosphorylation in T cells upon IL-6 stimulation. Moreover, MOG-reactive CD4+ T cells expanded in the presence of ketamine produced reduced amounts of Th17 cytokines, leading to diminished EAE severity when transferred into TCRβ-deficient mice in comparison to those treated with vehicle. These findings demonstrate that ketamine suppresses autoimmune Th17 cell responses by inhibiting the differentiation as well as the reactivation of Th17 cells.