CD1d-dependent immune suppression mediated by regulatory B cells through modulations of iNKT cells

IL-10-producing regulatory B cells exhibit functional defects and play a protective role in severe endotoxic shock

Dysregulated host immune homeostasis in sepsis is life-threatening even after a successfully treated bacterial infection. Lipopolysaccharide (LPS) is an endotoxin that is a major contributor to the aberrant immune responses and endotoxic shock in gram-negative bacterial sepsis. However, the current knowledge of the role of B cells in endotoxic shock is limited. Here, we report that CD1d expression in B cells and the percentage of CD5⁺CD1d^hi regulatory B (Breg) cells decreased in a mouse model of endotoxic shock. Interestingly, IL-10 but not FasL expression in CD5⁺CD1d^hi Breg cells in response to endotoxin was dramatically reduced in severe septic shock mice, and the regulatory function of CD5⁺CD1d^hi Breg cells in vitro to control the Th1 response was also diminished. Adoptive transfer of CD5⁺CD1d^hi Breg cells from healthy WT mice but not IL-10 deficient mice downregulated the IFN-γ secretion in CD4⁺ T cells and conferred protection against severe endotoxic shock in vivo. Our findings demonstrate the change and notable therapeutic potential of IL-10-producing Breg cells in endotoxic shock.

In silico analysis for development of epitopes-based peptide vaccine against Alkhurma hemorrhagic fever virus

Alkhurma hemorrhagic fever virus (ALKV) causes a fatal clinical disease in human beings of different tropical and sub-tropical regions. Recently, the ALKV epidemics have raised a great public health concern with the room for improvement in the essential therapeutic interventions. Despite increased realistic clinical cases of ALKV infection, the efficient vaccine or immunotherapy is not yet available to-date. Therefore, the current study aimed to analyze the envelope glycoprotein of ALKV for the development of B-cells and T-cells epitope-based peptide vaccine using the computational in silico method. Utilizing various immunoinformatics approaches, a total of 5 B-cells and 25 T-cells (MHC-I = 17, MHC-II = 8) epitope-based peptides were predicted in the current study. All predicted peptides had highest antigenicity and immunogenicity scores along with high binding affinity to human leukocyte antigen (HLA) class II alleles. Among 25T-cell epitopes, three peptides were found alike to have affinity to bind both MHC-I and MHC-II alleles. These outcomes suggested that these predicted epitopes could potentially be used in the development of an efficient vaccine against ALKV, which may enable to elicit both humoral and cell-mediated immunity. Although, these predicted peptides could be useful in designing a candidate vaccine for the prevention of ALKV; however, it's in vitro and in vivo assessments are prerequisite.Communicated by Ramaswamy H. Sarma.

Natural killer T cell activation increases iNOS+CD206- M1 macrophage and controls the growth of solid tumor

Background

NKT cells play an important role in anti-tumor immunity. Alpha-galactosylceramide (α-GalCer), a synthetic glycolipid is presented to natural killer T (NKT) cells by most antigen-presenting cells through CD1d molecules leading to activation of NKT cells. However, the precise mechanisms of how α-GalCer-activated NKT regulate the polarization of the macrophages and effector T cells in the solid tumor are not studied adequately.

Methods

We induced solid tumor in C57BL/6 mice by subcutaneous injection of B16F10 cell line (1 X 10⁶ cells) and monitored the tumor growth. Animals were given an intraperitoneal injection of α-GalCer (2 μg/injection) in 200 μl PBS on day + 1, + 5, + 10, + 15, and + 20 (with respect to tumor cell injection). Immune cells were characterized using flow cytometry and immunofluorescence staining. NK cells, Gr1⁺ cells, and F4/80⁺ macrophages in the mice were depleted by intravenous injection of cell-specific antibodies. Statistical analysis was performed using Student’s t-test or one-way ANOVA.

Results

Our results showed that intratumoral NKT cells have a lower frequency of CD69, CD25, CD122, and IFN-γR expression; produced less inflammatory cytokines such as IFN-γ, TNF-α, and GM-CSF; higher frequency CD62L⁺ NKT cells; and also showed reduced proliferation as compared to the splenic NKT cells. Mice treated with α-GalCer showed a significantly increased frequency of IFN-γ-producing NKT cells, CD8⁺ T cells, and effector Th1 cells. Depletion of NK cells in α-GalCer-treated mice showed a lower frequency of IFN-γ-producing CD4⁺ and CD8⁺ T cells in the tumor and prevented the α-GalCer-induced tumor growth. NKT cell activation with α-GalCer treatment significantly increased the iNOS⁺CD206⁻ M1-macrophages and reduced the iNOS⁻CD206⁺ M2-macrophages in the spleen and tumor, and depletion of F4/80⁺ macrophages prevented the α-GalCer-induced reduction in the tumor growth.

Conclusions

We showed that activation of NKT cell with α-GalCer modulates the frequency of M1-macrophages and effector Th1 cells in the secondary lymphoid tissues and tumor microenvironment and inhibit tumor growth. The finding suggests that activation of NKT cells with α-GalCer may provide an effective anti-cancer outcome.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0697-7) contains supplementary material, which is available to authorized users.

Alterations of the iNKT cell compartment in brain-injured patients

BACKGROUND

Brain injury (BI) induces a state of immunodepression leading to pneumonia. We investigated the invariant natural killer T (iNKT) cell compartment.

METHODS

This is an observational study in two surgical intensive care units (ICUs) of a single institution and a research laboratory. Clinical data and samples from a prospective cohort were extracted. Severe brain-injured patients (n = 33) and sex- and age-matched healthy donors (n = 40) were studied.

RESULTS

We observed the presence of IL-10 in serum, a loss of IFN-γ and IL-13 production by peripheral blood mononuclear cells (PBMCs) following IL-2 stimulation, and downregulation of HLA-DR expression on both monocytes and B cells early after BI. Inversely, CD1d, the HLA class I-like molecule involved in antigen presentation to iNKT cells, was over-expressed on patients' monocytes and B cells. The antigen-presenting activity to iNKT cells of PBMCs was increased in the patients who developed pneumonia, but not in those who remained free of infection. Frequencies of iNKT cells among PBMCs were dramatically decreased in patients regardless of their infection status. Following amplification, an increased frequency of CD4+ iNKT cells producing IL-4 was noticed in the group of patients free of infection compared with those who became infected and with healthy donors. Finally, serum from BI patients inhibited the iNKT cells' specific response as well as the non-specific IL-2 stimulation of PBMCs, and the expression of the beta-2 adrenergic receptor was elevated at the surface of patients T lymphocytes.

CONCLUSIONS

We observed severe alterations of the iNKT cell compartment, including the presence of inhibitory serum factors. We demonstrate for the first time that the decreased capacity to present antigens is not a generalized phenomenon because whereas the expression of HLA-DR molecules is decreased, the capacity for presenting glycolipids through CD1d expression is higher in patients.

Non-Antibody-Secreting Functions of B Cells and Their Contribution to Autoimmune Disease

B cells play multiple important roles in the pathophysiology of autoimmune disease. Beyond producing pathogenic autoantibodies, B cells can act as antigen-presenting cells and producers of cytokines, including both proinflammatory and anti-inflammatory cytokines. Here we review our current understanding of the non-antibody-secreting roles that B cells may play during development of autoimmunity, as learned primarily from reductionist preclinical models. Attention is also given to concepts emerging from clinical studies using B cell depletion therapy, which shed light on the roles of these mechanisms in human autoimmune disease.

A Threshold Model for T-Cell Activation in the Era of Checkpoint Blockade Immunotherapy

Continued discoveries of negative regulators of inflammatory signaling provide detailed molecular insights into peripheral tolerance and anti-tumor immunity. Accumulating evidence indicates that peripheral tolerance is maintained at multiple levels of immune responses by negative regulators of proinflammatory signaling, soluble anti-inflammatory factors, inhibitory surface receptors & ligands, and regulatory cell subsets. This review provides a global overview of these regulatory machineries that work in concert to maintain peripheral tolerance at cellular and host levels, focusing on the direct and indirect regulation of T cells. The recent success of checkpoint blockade immunotherapy (CBI) has initiated a dramatic shift in the paradigm of cancer treatment. Unprecedented responses to CBI have highlighted the central role of T cells in both anti-tumor immunity and peripheral tolerance and underscored the importance of T cell exhaustion in cancer. We discuss the therapeutic implications of modulating the negative regulators of T cell function for tumor immunotherapy with an emphasis on inhibitory surface receptors & ligands—central players in T cell exhaustion and targets of checkpoint blockade immunotherapies. We then introduce a Threshold Model for Immune Activation—the concept that these regulatory mechanisms contribute to defining a set threshold of immunogenic (proinflammatory) signaling required to elicit an anti-tumor or autoimmune response. We demonstrate the value of the Threshold Model in understanding clinical responses and immune related adverse events in the context of peripheral tolerance, tumor immunity, and the era of Checkpoint Blockade Immunotherapy.

CD1d highly expressed on DCs reduces lung tumor burden by enhancing antitumor immunity

Dendritic cells (DCs), as professional antigen-presenting cells are essential for the initial activation of adaptive antitumor immunity. CD1d is considered to present phospholipid and glycosphingolipid antigens to NKT cells. However, it is currently unknown whether CD1d expression on DCs is capable of enhancing antitumor immunity, particularly T-cell related immunity. We observed that CD1d was predominantly expressed on DCs in 3LL tumor-bearing mice, whilst a deficiency of CD1d promoted tumor growth. Notably, CD1d expression on DCs was not only required for presenting antigen to NKT cells, but also markedly promoted CD4⁺T and CD8⁺T cell activation, particularly cytotoxic T cells. All the T cells (NKT, CD4⁺T and CD8⁺T cells) upregulated CD69, CD107a and IFN-γ after the adoptive transfer of CD1d-positive DCs (CD1d⁺DCs) and tumor growth was suppressed. With regard to the mechanism, we revealed that CD1d⁺DCs were concomitant with a higher expression of costimulatory molecules (CD40, CD80 and CD86) and MHCI/II, which are essential for DCs to present antigens to T cells. Consistently, CD1d⁺DCs displayed stronger activation-associated-ERK1/2 and NF-κB signals; whereas JAK2-STAT3/6 signaling was required for maintaining a high level of CD1d on DCs. In lung cancer patients, the antitumor activities of all the T cells were enhanced with the increase of CD1d⁺DCs. Analysis of TCGA data revealed that high levels of CD1d indicated better outcomes for patients. Collectively, CD1d enhanced DC-based antitumor immunity, not only by targeting NKT, but also by activating CD4⁺T and CD8⁺T cells. CD1d⁺DCs may be superior to the bulk population of DCs in cancer immunotherapy.

Levels of regulatory T cells and invariant natural killer cells and their associations with regulatory B cells in patients with non-Hodgkin lymphoma

Due to their immunoregulatory properties, several specialized cell subsets, including regulatory T (Treg), invariant natural killer T (iNKT) and regulatory B (Breg) cells, are involved in the pathogenesis of non-Hodgkin lymphoma (NHL). However, the interaction between various cells remains to be elucidated. The aim of the present study was to evaluate the levels of Treg, iNKT and Breg cell subsets and their interrelationships in the peripheral blood (PB) and bone marrow (BM) of patients with B-cell NHL who received rituximab-based regimens and achieved a complete remission. A total of 20 patients and 20 healthy age- and sex-matched controls were prospectively enrolled for investigation of Treg, iNKT and Breg cell subsets in PB and BM by flow cytometry and cell culture. Prior to administration of combination chemotherapy with rituximab, the patients had lower levels of Breg cells and, to a lesser degree, Treg cells, but not iNKT cells, in PB compared with controls. Compartmental differences in the levels of Treg and Breg cell subsets, but not iNKT cells, were observed between PB and BM, suggesting an increase in trafficking through the blood of these regulatory cell subsets to the marrow. Following complete remission, the levels of circulating Treg, iNKT and Breg cell subsets increased. The levels of Treg cells were not significantly associated with iNKT and Breg cell subsets, although negative correlations were observed. Taken together, these results may provide new insights into the potential role of regulatory cell subsets in patients with B-cell NHL. However, whether the observed differences between PB and BM may affect clinical outcomes requires further investigation.

A new perspective: Exploring future therapeutic strategies for cancer by understanding the dual role of B lymphocytes in tumor immunity

Our previous understanding of the role of B lymphocytes in tumor immunity is its antitumor effects. However, further evidence indicates B lymphocytes can also promote tumorigenesis by modulating immune responses. Therefore, the increasingly complex role of B lymphocytes in tumor immunity may become an important factor in tumor immunotherapy. In this review, we describe the development of B cells in tumor microenvironments. We then focus on the most controversial issues of the biological functions of B lymphocytes. Finally, we nominate B cells as therapeutic targets, which should open broad perspectives for the development of their clinical applications.

The Multifaceted B Cell Response in Allergen Immunotherapy

While allergen immunotherapy (AIT) for IgE-mediated diseases holds curative potential, the considerable heterogeneity in clinical outcomes may relate to the complex mechanisms of tolerance. The regulation of humoral immunity by AIT contributes to the suppression of allergic responses. Recent findings have revealed novel roles for IgA and IgG antibodies in the induction of tolerance. These mechanisms synergize with their ability to block allergen-IgE binding and mediate inhibitory signaling of effector cells of the allergic response. In addition, the regulatory activity of B cells in AIT extends beyond IL-10 secretion and induction of IgG₄. Here, we review the evolution of the B cell response during AIT with special emphasis on the novel protective mechanisms entailing humoral immunity.

Altered thymic differentiation and modulation of arthritis by invariant NKT cells expressing mutant ZAP70

Various subsets of invariant natural killer T (iNKT) cells with different cytokine productions develop in the mouse thymus, but the factors driving their differentiation remain unclear. Here we show that hypomorphic alleles of Zap70 or chemical inhibition of Zap70 catalysis leads to an increase of IFN-γ-producing iNKT cells (NKT1 cells), suggesting that NKT1 cells may require a lower TCR signal threshold. Zap70 mutant mice develop IL-17-dependent arthritis. In a mouse experimental arthritis model, NKT17 cells are increased as the disease progresses, while NKT1 numbers negatively correlates with disease severity, with this protective effect of NKT1 linked to their IFN-γ expression. NKT1 cells are also present in the synovial fluid of arthritis patients. Our data therefore suggest that TCR signal strength during thymic differentiation may influence not only IFN-γ production, but also the protective function of iNKT cells in arthritis.

Invariant natural killer T (iNKT) cells can be subsetted based on their cytokine productions. Here the authors show, using Zap70 mutant mice, that interferon-γ secreting (IFN-γ) iNKT cells may be induced by hampered T cell receptor signallings to help ameliorate interleukin-17-mediated joint inflammation.