Interleukin-21 Is Critically Required in Autoimmune and Allogeneic Responses to Islet Tissue in Murine Models

OBJECTIVE-Type 1 diabetes is an incurable chronic autoimmune disease. Although transplantation of pancreatic islets may serve as a surrogate source of insulin, recipients are subjected to a life of immunosuppression. Interleukin (IL)-21 is necessary for type 1 diabetes in NOD mice. We examined the efficacy of an IL-21-targeted therapy on prevention of diabetes in NOD mice, in combination with syngeneic islet transplantation. In addition, we assessed the role of IL-21 responsiveness in islet allograft rejection in mouse animal models. RESEARCH DESIGN AND METHODS-NOD mice were treated with IL-21R/Fc, an IL-21-neutralizing chimeric protein. This procedure was combined with syngeneic islet transplantation to treat diabetic NOD mice. Survival of allogeneic islet grafts in IL-21R-deficient mice was also assessed. RESULTS-Evidence is provided that IL-21 is continually required by the autoimmune infiltrate, such that insulitis was reduced and reversed and diabetes inhibited by neutralization of IL-21 at a late preclinical stage. Recovery from autoimmune diabetes was achieved by combining neutralization of IL-21 with islet transplantation. Furthermore, IL-21-responsiveness by CD8+ T-cells was sufficient to mediate islet allograft rejection. CONCLUSIONS-Neutralization of IL-21 in NOD mice can inhibit diabetes, and when paired with islet transplantation, this therapeutic approach restored normoglycemia. The influence of IL-21 on a graft-mounted immune response was robust, since the absence of IL-21 signaling prevented islet allograft rejection. These findings suggest that therapeutic manipulation of IL-21 may serve as a suitable treatment for patients with type 1 diabetes. Diabetes 60:867-875, 20111151sciescopu

IL-21 restricts T follicular regulatory T cell proliferation through Bcl-6 mediated inhibition of responsiveness to IL-2

T follicular regulatory (Tfr) cells control the magnitude and specificity of the germinal centre reaction, but how regulation is contained to ensure generation of high-affinity antibody is unknown. Here we show that this balance is maintained by the reciprocal influence of interleukin (IL)-2 and IL-21. The number of IL-2-dependent FoxP3+ regulatory T cells is increased in the peripheral blood of human patients with loss-of-function mutations in the IL-21 receptor (IL-21R). In mice, IL-21:IL-21R interactions influence the phenotype of T follicular cells, reducing the expression of CXCR4 and inhibiting the expansion of Tfr cells after T-cell-dependent immunization. The negative effect of IL-21 on Tfr cells in mice is cell intrinsic and associated with decreased expression of the high affinity IL-2 receptor (CD25). Bcl-6, expressed in abundance in Tfr cells, inhibits CD25 expression and IL-21-mediated inhibition of CD25 is Bcl-6 dependent. These findings identify a mechanism by which IL-21 reinforces humoral immunity by restricting Tfr cell proliferation

IL-21 restricts T follicular regulatory T cell proliferation through Bcl-6 mediated inhibition of responsiveness to IL-2

T follicular regulatory (Tfr) cells control the magnitude and specificity of the germinal centre reaction, but how regulation is contained to ensure generation of high-affinity antibody is unknown. Here we show that this balance is maintained by the reciprocal influence of interleukin (IL)-2 and IL-21. The number of IL-2-dependent FoxP3(+) regulatory T cells is increased in the peripheral blood of human patients with loss-of-function mutations in the IL-21 receptor (IL-21R). In mice, IL-21: IL-21R interactions influence the phenotype of T follicular cells, reducing the expression of CXCR4 and inhibiting the expansion of Tfr cells after T-cell-dependent immunization. The negative effect of IL-21 on Tfr cells in mice is cell intrinsic and associated with decreased expression of the high affinity IL-2 receptor (CD25). Bcl-6, expressed in abundance in Tfr cells, inhibits CD25 expression and IL-21-mediated inhibition of CD25 is Bcl-6 dependent. These findings identify a mechanism by which IL-21 reinforces humoral immunity by restricting Tfr cell proliferation.This work was supported by grants from the Diabetes Australia Research Trust and the National Health and Medical Research Council

B cell-derived GABA elicits IL-10⁺ macrophages to limit anti-tumour immunity

GABAを標的とする抗腫瘍免疫機構 --代謝産物を介した免疫細胞間制御の一端を解明--. 京都大学プレスリリース. 2021-11-10.Small, soluble metabolites not only are essential intermediates in intracellular biochemical processes, but can also influence neighbouring cells when released into the extracellular milieu1-3. Here we identify the metabolite and neurotransmitter GABA as a candidate signalling molecule synthesized and secreted by activated B cells and plasma cells. We show that B cell-derived GABA promotes monocyte differentiation into anti-inflammatory macrophages that secrete interleukin-10 and inhibit CD8⁺ T cell killer function. In mice, B cell deficiency or B cell-specific inactivation of the GABA-generating enzyme GAD67 enhances anti-tumour responses. Our study reveals that, in addition to cytokines and membrane proteins, small metabolites derived from B-lineage cells have immunoregulatory functions, which may be pharmaceutical targets allowing fine-tuning of immune responses

Interleukin 21 in immunity and autoimmunity

T cell help to B cells is a fundamental property of adaptive immunity, yet only recentlyhave many of the cellular and molecular mechanisms of T cell help emerged. T follicular helper (Tfh) cells are the CD4+ T helper cells that provide cognate help to B cells for high affinity antibody production in germinal centres (GC). This study has reveals a critical role of IL-21 in the upregulation of Tfh signature molecules. Expression of ICOS was found to be necessary for optimal production of IL-21; indicative of interplay between two Tfh expressed molecules. We also demonstrate that IL-21's costimulatory capacity for T helper differentiation operates at the level of the TCR through Vav1 signalling that controls T cell helper function and survival. Tfh cells express uniquely high levels of the IL-21 receptor relative to other T cell subsets, which reflects an IL-21-driven autocrine loop that is important for the generation and function of Tfh cells, which in turn were critical for supporting primary and secondary T dependent antibody responses. This study reveals a previously unappreciated role for Tfh cells in the formation of the GC through a CD4+ Tcell intrinsic requirement for responsiveness to IL-21.IL-2 and IL-21 are crucial growth factors for distinct T helper subsets with opposing regulatory and effector functions, respectively. Mice made genetically deficient in IL-2 or its high affinity receptor chain (CD25) suffer from a fatal autoimmune disease characterized by ulcerative colitis and haemolytic anaemia. The observed autoimmunity and associated splenomegally are thought to be caused, in part, by a loss of regulation of effector T cells due to a deficit in IL-2-dependent Foxp3 regulatory T cells. Since IL-21 is known to facilitate the development of a number of autoimmune diseases, the possible contribution of IL-21 to the autoimmune pathology observed in Il2-/- mice was investigated in this study. Our findings demonstrate that IL-21:IL-21R signalling contributes to the destruction of tissues attributed to autoimmunity in Il2-/- mice and suggests that IL-21-producing T cells are significant targets of immune system regulation

A Fundamental Role for Interleukin-21 in the Generation of T Follicular Helper Cells

SummaryT cell help to B cells is a fundamental property of adaptive immunity, yet only recently have many of the cellular and molecular mechanisms of T cell help emerged. T follicular helper (Tfh) cells are the CD4+ T helper cells that provide cognate help to B cells for high-affinity antibody production in germinal centers (GC). Tfh cells produce interleukin-21 (IL-21), and we show that IL-21 was necessary for GC formation. However, the central role of IL-21 in GC formation reflected its effects on Tfh cell generation rather than on B cells. Expression of the inducible costimulator (ICOS) was necessary for optimal production of IL-21, indicative of interplay between these two Tfh cell-expressed molecules. Finally, we demonstrate that IL-21's costimulatory capacity for T helper cell differentiation operated at the level of the T cell receptor signalosome through Vav1, a signaling molecule that controls T cell helper function. This study reveals a previously unappreciated role for Tfh cells in the formation of the GC and isotype switching through a CD4+ T cell-intrinsic requirement for IL-21

Mucosal BCG Vaccination Induces Protective Lung-Resident Memory T Cell Populations against Tuberculosis

Mycobacterium bovis Bacille Calmette-Guééérin (BCG) is the only licensed vaccine against tuberculosis (TB), yet its moderate efficacy against pulmonary TB calls for improved vaccination strategies. Mucosal BCG vaccination generates superior protection against TB in animal models; however, the mechanisms of protection remain elusive. Tissue-resident memory T (TRM) cells have been implicated in protective immune responses against viral infections, but the role of TRM cells following mycobacterial infection is unknown. Using a mouse model of TB, we compared protection and lung cellular infiltrates of parenteral and mucosal BCG vaccination. Adoptive transfer and gene expression analyses of lung airway cells were performed to determine the protective capacities and phenotypes of different memory T cell subsets. In comparison to subcutaneous vaccination, intratracheal and intranasal BCG vaccination generated T effector memory and TRM cells in the lung, as defined by surface marker phenotype. Adoptive mucosal transfer of these airway-resident memory T cells into naive mice mediated protection against TB. Whereas airway-resident memory CD4+ T cells displayed a mixture of effector and regulatory phenotype, airway-resident memory CD8+ T cells displayed prototypical TRM features. Our data demonstrate a key role for mucosal vaccination-induced airway-resident T cells in the host defense against pulmonary TB. These results have direct implications for the design of refined vaccination strategies

Generation and validation of BCG Δ<i>ureC</i>::<i>hly</i>_<i>hIL7</i> and BCG Δ<i>ureC</i>::<i>hly</i>_<i>hIL18</i>.

<p><b>A</b>. Organisation of the cytokine expression cassette for stable transformation of BCG Δ<i>ureC</i>::<i>hly</i>. <b>B</b>. Confirmation of hIL-7 and hIL-18 gene presence (gDNA as template) and transcription (cDNA as template) in BCG Δ<i>ureC:hly_hIL7</i> or BCG Δ<i>ureC:hly_hIL18</i>, respectively using PCR or RT-PCR. <b>C</b>. Confirmation of hIL-18 and hIL-7 protein expression by the respective strains using ELISA. Experiments were performed twice with similar outcome.</p