Publications by authors named "Stephen R Daley"

23 Publications

  • Page 1 of 1

c-Rel employs multiple mechanisms to promote the thymic development and peripheral function of regulatory T cells in mice.

Eur J Immunol 2021 May 7. Epub 2021 May 7.

Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia.

The NF-κB transcription factor c-Rel is a critical regulator of Treg ontogeny, controlling multiple points of the stepwise developmental pathway. Here, we found that the thymic Treg defect in c-Rel-deficient (cRel ) mice is quantitative, not qualitative, based on analyses of TCR repertoire and TCR signaling strength. However, these parameters are altered in the thymic Treg-precursor population, which is also markedly diminished in cRel mice. Moreover, c-Rel governs the transcriptional programme of both thymic and peripheral Tregs, controlling a core of genes involved with immune signaling, and separately in the periphery, cell cycle progression. Last, the immune suppressive function of peripheral cRel tTregs is diminished in a lymphopenic model of T cell proliferation and is associated with decreased stability of Foxp3 expression. Collectively, we show that c-Rel is a transcriptional regulator that controls multiple aspects of Treg development, differentiation, and function via distinct mechanisms.
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http://dx.doi.org/10.1002/eji.202048900DOI Listing
May 2021

SASH3 variants cause a novel form of X-linked combined immunodeficiency with immune dysregulation.

Blood 2021 Apr 19. Epub 2021 Apr 19.

Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States.

SAM and SH3 domain-containing 3 (SASH3), also called SH3-containing Lymphocyte Protein (SLY1) is a putative adaptor protein that is postulated to play an important role in the organization of signaling complexes and propagation of signal transduction cascades in lymphocytes. The SASH3 gene is located on the X-chromosome. Here, we identified three novel SASH3 deleterious variants in four unrelated male patients with a history of combined immunodeficiency and immune dysregulation manifesting as recurrent sinopulmonary, cutaneous and mucosal infections, and refractory autoimmune cytopenias. Patients exhibited CD4+ T cell lymphopenia, decreased T cell proliferation and cell cycle progression, and increased T cell apoptosis in response to mitogens. In vitro T-cell differentiation of CD34+ cells and molecular signatures of rearrangements at the T-cell receptor alpha (TRA) locus were indicative of impaired thymocyte survival. These patients also manifested neutropenia and B and NK cell lymphopenia. Lentivirus-mediated transfer of the SASH3 cDNA corrected protein expression, in vitro proliferation and signaling in SASH3-deficient Jurkat and patient-derived T cells. These findings define a new type of X-linked combined immunodeficiency in humans that recapitulates many of the abnormalities reported in Sly1-/- and Sly1D/Dmutant mice, highlighting an important role of SASH3 in human lymphocyte function and survival.
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http://dx.doi.org/10.1182/blood.2020008629DOI Listing
April 2021

DOCK8 deficiency diminishes thymic T-regulatory cell development but not thymic deletion.

Clin Transl Immunology 2021 7;10(1):e1236. Epub 2021 Jan 7.

Infection and Immunity Program Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology Monash University Melbourne VIC Australia.

Objective: To define the effect of DOCK8 deficiency on thymic tolerance in mice.

Methods: Thymocytes from wild-type ( ) and DOCK8-deficient ( ) mice were examined by flow cytometry. Some mice had transgenic expression of the BCL2 anti-apoptotic protein in haemopoietic cells. Some mice expressed the transgenic 3A9 T-cell receptor (TCR), which triggers thymocyte deletion in mice also expressing hen egg lysozyme under the insulin promoter.

Results: In mice, the proportion of thymocytes induced to acquire tolerance at the immature CCR7 stage was normal. Deletion of strongly self-reactive CD4 thymocytes occurred efficiently in mice in a TCR-transgenic model that requires self-antigen transfer from epithelial cells to bone marrow (BM)-derived antigen-presenting cells. Thymic Foxp3 T-regulatory cells (T) and Helios Foxp3 T precursors were decreased in mice, including when apoptosis was inhibited by BCL2 transgene expression. thymic T expressed CD25 and CTLA-4 at normal levels. The results suggest that DOCK8 deficiency does not affect the function of BM-derived antigen-presenting cells in the thymus, the TCR self-reactivity threshold that activates tolerance mechanisms in thymocytes or the apoptotic deletion of these thymocytes. However, DOCK8 is required to prevent a subset of developing T cells from undergoing cell death via a mechanism that is distinct from apoptosis.

Conclusion: DOCK8 deficiency diminishes T development in the thymus without compromising thymocyte deletion.
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http://dx.doi.org/10.1002/cti2.1236DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7790591PMC
January 2021

Nfkb2 variants reveal a p100-degradation threshold that defines autoimmune susceptibility.

J Exp Med 2021 Feb;218(2)

Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, Australia.

NF-κB2/p100 (p100) is an inhibitor of κB (IκB) protein that is partially degraded to produce the NF-κB2/p52 (p52) transcription factor. Heterozygous NFKB2 mutations cause a human syndrome of immunodeficiency and autoimmunity, but whether autoimmunity arises from insufficiency of p52 or IκB function of mutated p100 is unclear. Here, we studied mice bearing mutations in the p100 degron, a domain that harbors most of the clinically recognized mutations and is required for signal-dependent p100 degradation. Distinct mutations caused graded increases in p100-degradation resistance. Severe p100-degradation resistance, due to inheritance of one highly degradation-resistant allele or two subclinical alleles, caused thymic medullary hypoplasia and autoimmune disease, whereas the absence of p100 and p52 did not. We inferred a similar mechanism occurs in humans, as the T cell receptor repertoires of affected humans and mice contained a hydrophobic signature of increased self-reactivity. Autoimmunity in autosomal dominant NFKB2 syndrome arises largely from defects in nonhematopoietic cells caused by the IκB function of degradation-resistant p100.
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http://dx.doi.org/10.1084/jem.20200476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595743PMC
February 2021

The Impact of MHC Class I Dose on Development and Maintenance of the Polyclonal Naive CD8 T Cell Repertoire.

J Immunol 2020 06 27;204(12):3108-3116. Epub 2020 Apr 27.

Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia;

Naive CD8 T cell survival in the periphery is critically dependent on tonic TCR signaling through peptide + MHC class I (MHCI) recognition; however, little is known about how natural variation in MHCI levels impacts the naive CD8 T cell repertoire. Using mice that are hemizygous or homozygous for a single MHCI allele, we showed that despite a reduction in peripheral CD8 T cell numbers of ∼50% in MHCI hemizygous mice, MHCI levels had no notable impact on the rate of thymic generation or emigration of CD8 single-positive T cells. Moreover, the peripheral T cell repertoire in hemizygous mice showed selective retention of T cell clonotypes with a greater competitive advantage as evidenced by increased expression of CD5 and IL-7Rα. The qualitative superiority of CD8 T cells retained in hemizygous mice was also seen during influenza A virus infection, in which epitope-specific CD8 T cells from hemizygous mice had a higher avidity for pMHCI and increased cytokine polyfunctionality, despite a reduced response magnitude. Collectively, this study suggests that natural variation in MHCI expression levels has a notable and biologically relevant impact on the maintenance, but not generation, of the naive CD8 T cell repertoire.
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http://dx.doi.org/10.4049/jimmunol.2000081DOI Listing
June 2020

Denisovan, modern human and mouse TNFAIP3 alleles tune A20 phosphorylation and immunity.

Nat Immunol 2019 10 18;20(10):1299-1310. Epub 2019 Sep 18.

Research School of Chemistry, The Australian National University, Canberra, Australian Capital Territory, Australia.

Resisting and tolerating microbes are alternative strategies to survive infection, but little is known about the evolutionary mechanisms controlling this balance. Here genomic analyses of anatomically modern humans, extinct Denisovan hominins and mice revealed a TNFAIP3 allelic series with alterations in the encoded immune response inhibitor A20. Each TNFAIP3 allele encoded substitutions at non-catalytic residues of the ubiquitin protease OTU domain that diminished IκB kinase-dependent phosphorylation and activation of A20. Two TNFAIP3 alleles encoding A20 proteins with partial phosphorylation deficits seemed to be beneficial by increasing immunity without causing spontaneous inflammatory disease: A20 T108A;I207L, originating in Denisovans and introgressed in modern humans throughout Oceania, and A20 I325N, from an N-ethyl-N-nitrosourea (ENU)-mutagenized mouse strain. By contrast, a rare human TNFAIP3 allele encoding an A20 protein with 95% loss of phosphorylation, C243Y, caused spontaneous inflammatory disease in humans and mice. Analysis of the partial-phosphorylation A20 I325N allele in mice revealed diminished tolerance of bacterial lipopolysaccharide and poxvirus inoculation as tradeoffs for enhanced immunity.
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http://dx.doi.org/10.1038/s41590-019-0492-0DOI Listing
October 2019

Deletion of self-reactive CCR7- thymocytes in the absence of MHC expression on thymic epithelial cells.

Cell Death Differ 2019 12 24;26(12):2727-2739. Epub 2019 Apr 24.

Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, Australia.

The selection of αβ T cells in the thymus is punctuated by checkpoints at which thymocytes differentiate or undergo apoptosis. Wave 1 deletion is defined as apoptosis within nascent αβ T-cell antigen receptor (TCR)-signalled thymocytes that lack CCR7 expression. The antigen-presenting cell (APC) types that mediate wave 1 deletion are unclear. To measure wave 1 deletion, we compared the frequencies of TCRβ + CD5 + Helios + CCR7- cells in nascent thymocyte cohorts in mice with normal or defective apoptosis. This thymocyte population is small in mice lacking major histocompatibility complex (MHC) expression. The scale of wave 1 deletion was increased by transgenic expression of the self-reactive Yae62 TCRβ chain, was almost halved when haemopoietic APCs lacked MHC expression and, surprisingly, was unchanged when epithelial cells lacked MHC expression. These findings demonstrate efficiency, and some redundancy, in the APC types that mediate wave 1 deletion in the normal mouse thymus.
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http://dx.doi.org/10.1038/s41418-019-0331-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224288PMC
December 2019

αβ T-cell receptors with a central CDR3 cysteine are enriched in CD8αα intraepithelial lymphocytes and their thymic precursors.

Immunol Cell Biol 2018 07 3;96(6):553-561. Epub 2018 May 3.

Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia.

The thymus plays a crucial role in immune tolerance by exposing developing T cells (thymocytes) to a myriad of self-antigens. Strong T-cell receptor (TCR) engagement induces tolerance in self-reactive thymocytes by stimulating apoptosis or selection into specialized T-cell lineages, including intestinal TCRαβ CD8αα intraepithelial lymphocytes (IEL). TCR-intrinsic amino acid motifs that can be used to predict whether a TCR will be strongly self-reactive remain elusive. Here, a novel TCR sequence alignment approach revealed that T-cell lineages in C57BL/6 mice had divergent usage of cysteine within two positions of the amino acid at the apex of the complementarity-determining region 3 (CDR3) of the TCRα or TCRβ chain. Compared to pre-selection thymocytes, central CDR3 cysteine usage was increased in IEL and Type A IEL precursors (IELp) and markedly decreased in Foxp3 regulatory T cells (T-reg) and naïve T cells. These findings reveal a TCR-intrinsic motif that distinguishes Type A IELp and IEL from T-reg and naïve T cells.
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http://dx.doi.org/10.1111/imcb.12047DOI Listing
July 2018

Understanding the drivers of MHC restriction of T cell receptors.

Nat Rev Immunol 2018 07;18(7):467-478

Infection and Immunity Program and Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia.

T cell discrimination of self and non-self is predicated on αβ T cell receptor (TCR) co-recognition of peptides presented by MHC molecules. Over the past 20 years, structurally focused investigations into this MHC-restricted response have provided profound insights into T cell function. Simultaneously, two models of TCR recognition have emerged, centred on whether the TCR has, through evolution, acquired an intrinsic germline-encoded capacity for MHC recognition or whether MHC reactivity is conferred by developmental selection of TCRs. Here, we review the structural and functional data that pertain to these theories of TCR recognition, which indicate that it will be necessary to assimilate features of both models to fully account for the molecular drivers of this evolutionarily ancient interaction between the TCR and MHC molecules.
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http://dx.doi.org/10.1038/s41577-018-0007-5DOI Listing
July 2018

Indirect presentation in the thymus limits naive and regulatory T-cell differentiation by promoting deletion of self-reactive thymocytes.

Immunology 2018 07 27;154(3):522-532. Epub 2018 Feb 27.

Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia.

Acquisition of T-cell central tolerance involves distinct pathways of self-antigen presentation to thymocytes. One pathway termed indirect presentation requires a self-antigen transfer step from thymic epithelial cells (TECs) to bone marrow-derived cells before the self-antigen is presented to thymocytes. The role of indirect presentation in central tolerance is context-dependent, potentially due to variation in self-antigen expression, processing and presentation in the thymus. Here, we report experiments in mice in which TECs expressed a membrane-bound transgenic self-antigen, hen egg lysozyme (HEL), from either the insulin (insHEL) or thyroglobulin (thyroHEL) promoter. Intrathymic HEL expression was less abundant and more confined to the medulla in insHEL mice compared with thyroHEL mice. When indirect presentation was impaired by generating mice lacking MHC class II expression in bone marrow-derived antigen-presenting cells, insHEL-mediated thymocyte deletion was abolished, whereas thyroHEL-mediated deletion occurred at a later stage of thymocyte development and Foxp3 regulatory T-cell differentiation increased. Indirect presentation increased the strength of T-cell receptor signalling that both self-antigens induced in thymocytes, as assessed by Helios expression. Hence, indirect presentation limits the differentiation of naive and regulatory T cells by promoting deletion of self-reactive thymocytes.
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http://dx.doi.org/10.1111/imm.12904DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6002238PMC
July 2018

Ocular antigen does not cause disease unless presented in the context of inflammation.

Sci Rep 2017 10 27;7(1):14226. Epub 2017 Oct 27.

Immunology and Virology Program, Centre for Ophthalmology and Visual Science, The University of Western Australia, Crawley, Western Australia, Australia.

Ocular antigens are sequestered behind the blood-retina barrier and the ocular environment protects ocular tissues from autoimmune attack. The signals required to activate autoreactive T cells and allow them to cause disease in the eye remain in part unclear. In particular, the consequences of peripheral presentation of ocular antigens are not fully understood. We examined peripheral expression and presentation of ocular neo-self-antigen in transgenic mice expressing hen egg lysozyme (HEL) under a retina-specific promoter. High levels of HEL were expressed in the eye compared to low expression throughout the lymphoid system. Adoptively transferred naïve HEL-specific CD4 T cells proliferated in the eye draining lymph nodes, but did not induce uveitis. By contrast, systemic infection with a murine cytomegalovirus (MCMV) engineered to express HEL induced extensive proliferation of transferred naïve CD4 T cells, and significant uveoretinitis. In this model, wild-type MCMV, lacking HEL, did not induce overt uveitis, suggesting that disease is mediated by antigen-specific peripherally activated CD4 T cells that infiltrate the retina. Our results demonstrate that retinal antigen is presented to T cells in the periphery under physiological conditions. However, when the same antigen is presented during viral infection, antigen-specific T cells access the retina and autoimmune uveitis ensues.
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http://dx.doi.org/10.1038/s41598-017-14618-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5660195PMC
October 2017

Cell death and thymic tolerance.

Immunol Rev 2017 05;277(1):9-20

The Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia.

The differentiation of hematopoietic precursors into the many functionally distinct T-cell types produced by the thymus is a complex process. It proceeds through a series of stages orchestrated by a variety of thymic microenvironments that shape the T-cell developmental processes. Numerous cytokine and cell surface receptors direct thymocyte differentiation but the primary determinant of cell fate is the engagement of the T-cell antigen receptor (TCR). The strength of the TCR signal and the maturation stage of the thymocyte receiving it can direct the various differentiation programs or, alternatively, end the process by inducing cell death. The regulation of thymocyte death is critical for the efficiency of thymic T-cell differentiation and the preservation of immune tolerance. A detailed knowledge of mechanisms that eliminate thymocytes from the T-cell repertoire is essential to understand the "logic" of T-cell selection in the thymus. This review focuses on the central role of the BCL-2 family of proteins in the apoptotic checkpoints that punctuate thymocyte differentiation and the consequences of defects in these processes.
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http://dx.doi.org/10.1111/imr.12532DOI Listing
May 2017

IL-2 prevents deletion of developing T-regulatory cells in the thymus.

Cell Death Differ 2017 06 12;24(6):1007-1016. Epub 2017 May 12.

Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra 0200, Australia.

In the thymus, strongly self-reactive T cells may undergo apoptotic deletion or differentiate into Foxp3+ T-regulatory (T-reg) cells. Mechanisms that partition T cells into these two fates are unclear. Here, we show that IL-2 signalling is required to prevent deletion of CD4+ CD8- CCR7+ Helios+ thymocytes poised to upregulate Foxp3. The deletion prevented by IL-2 signalling is Foxp3 independent and occurs later in thymocyte development than the deletion that is prevented by Card11 signalling. Our results distinguish two bottlenecks at which strongly self-reactive thymocytes undergo deletion or progress to the next stage of T-reg differentiation; Card11 regulates the first bottleneck and IL-2 regulates the second.
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http://dx.doi.org/10.1038/cdd.2017.38DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5442470PMC
June 2017

A timeline demarcating two waves of clonal deletion and Foxp3 upregulation during thymocyte development.

Immunol Cell Biol 2016 Apr 29;94(4):357-66. Epub 2015 Oct 29.

Immunology Department, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.

Thymocytes that bind strongly to self-antigens are prevented from becoming naive T cells by several mechanisms. They undergo clonal deletion at two stages of development; wave 1 in immature thymocytes lacking the medulla-homing chemokine receptor, CCR7, or wave 2 in more mature CCR7(+) thymocytes. Alternatively, self-reactive thymocytes upregulate Foxp3 to become T-regulatory cells. Here, we describe the differential timing of the two waves of deletion and Foxp3 upregulation relative to the immature proliferating stage. Proliferating thymocytes were pulse-labeled in normal C57BL/6 mice with 5-ethynyl-2'-deoxyuridine (EdU). Thymocytes progressed into wave 1 (CCR7(-)) and wave 2 (CCR7(+)) of clonal deletion ~2 and 5 days after proliferation, respectively. Foxp3 upregulation occurred between 4 and 8 days after proliferation, predominantly in thymocytes with a Helios(+) CCR7(+) phenotype. These findings establish a timeline that suggests that wave 1 of clonal deletion occurs in the thymic cortex, whereas wave 2 and Foxp3 upregulation both occur in the thymic medulla.
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http://dx.doi.org/10.1038/icb.2015.95DOI Listing
April 2016

MHCI and CD8 lineage commitment. Prolonged access to thymic epithelial MHCI seals CD8⁺ lineage commitment.

Authors:
Stephen R Daley

Immunol Cell Biol 2015 Apr 10;93(4):326-7. Epub 2015 Mar 10.

Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.

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http://dx.doi.org/10.1038/icb.2015.28DOI Listing
April 2015

Quantitative reduction of the TCR adapter protein SLP-76 unbalances immunity and immune regulation.

J Immunol 2015 Mar 6;194(6):2587-95. Epub 2015 Feb 6.

Department of Immunology, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia;

Gene variants that disrupt TCR signaling can cause severe immune deficiency, yet less disruptive variants are sometimes associated with immune pathology. Null mutations of the gene encoding the scaffold protein Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76), for example, cause an arrest of T cell positive selection, whereas a synthetic membrane-targeted allele allows limited positive selection but is associated with proinflammatory cytokine production and autoantibodies. Whether these and other enigmatic outcomes are due to a biochemical uncoupling of tolerogenic signaling, or simply a quantitative reduction of protein activity, remains to be determined. In this study we describe a splice variant of Lcp2 that reduced the amount of wild-type SLP-76 protein by ~90%, disrupting immunogenic and tolerogenic pathways to different degrees. Mutant mice produced excessive amounts of proinflammatory cytokines, autoantibodies, and IgE, revealing that simple quantitative reductions of SLP-76 were sufficient to trigger immune dysregulation. This allele reveals a dose-sensitive threshold for SLP-76 in the balance of immunity and immune dysregulation, a common disturbance of atypical clinical immune deficiencies.
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http://dx.doi.org/10.4049/jimmunol.1400326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4355390PMC
March 2015

Ndfip1 mediates peripheral tolerance to self and exogenous antigen by inducing cell cycle exit in responding CD4+ T cells.

Proc Natl Acad Sci U S A 2014 Feb 13;111(6):2067-74. Epub 2014 Jan 13.

John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia.

The NDFIP1 (neural precursor cell expressed, developmentally down-regulated protein 4 family-interacting protein 1) adapter for the ubiquitin ligase ITCH is genetically linked to human allergic and autoimmune disease, but the cellular mechanism by which these proteins enable foreign and self-antigens to be tolerated is unresolved. Here, we use two unique mouse strains--an Ndfip1-YFP reporter and an Ndfip1-deficient strain--to show that Ndfip1 is progressively induced during T-cell differentiation and activation in vivo and that its deficiency causes a cell-autonomous, Forkhead box P3-independent failure of peripheral CD4(+) T-cell tolerance to self and exogenous antigen. In small cohorts of antigen-specific CD4(+) cells responding in vivo, Ndfip1 was necessary for tolerogen-reactive T cells to exit cell cycle after one to five divisions and to abort Th2 effector differentiation, defining a step in peripheral tolerance that provides insights into the phenomenon of T-cell anergy in vivo and is distinct from the better understood process of Bcl2-interacting mediator of cell death-mediated apoptosis. Ndfip1 deficiency precipitated autoimmune pancreatic destruction and diabetes; however, this depended on a further accumulation of nontolerant anti-self T cells from strong stimulation by exogenous tolerogen. These findings illuminate a peripheral tolerance checkpoint that aborts T-cell clonal expansion against allergens and autoantigens and demonstrate how hypersensitive responses to environmental antigens may trigger autoimmunity.
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http://dx.doi.org/10.1073/pnas.1322739111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3926078PMC
February 2014

Rasgrp1 mutation increases naive T-cell CD44 expression and drives mTOR-dependent accumulation of Helios⁺ T cells and autoantibodies.

Elife 2013 Dec 12;2:e01020. Epub 2013 Dec 12.

Department of Immunology, John Curtin School of Medical Research, The Australian National University, Canberra, Australia.

Missense variants are a major source of human genetic variation. Here we analyze a new mouse missense variant, Rasgrp1(Anaef), with an ENU-mutated EF hand in the Rasgrp1 Ras guanine nucleotide exchange factor. Rasgrp1(Anaef) mice exhibit anti-nuclear autoantibodies and gradually accumulate a CD44(hi) Helios(+) PD-1(+) CD4(+) T cell population that is dependent on B cells. Despite reduced Rasgrp1-Ras-ERK activation in vitro, thymocyte selection in Rasgrp1(Anaef) is mostly normal in vivo, although CD44 is overexpressed on naïve thymocytes and T cells in a T-cell-autonomous manner. We identify CD44 expression as a sensitive reporter of tonic mTOR-S6 kinase signaling through a novel mouse strain, chino, with a reduction-of-function mutation in Mtor. Elevated tonic mTOR-S6 signaling occurs in Rasgrp1(Anaef) naïve CD4(+) T cells. CD44 expression, CD4(+) T cell subset ratios and serum autoantibodies all returned to normal in Rasgrp1(Anaef)Mtor(chino) double-mutant mice, demonstrating that increased mTOR activity is essential for the Rasgrp1(Anaef) T cell dysregulation. DOI: http://dx.doi.org/10.7554/eLife.01020.001.
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http://dx.doi.org/10.7554/eLife.01020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3858598PMC
December 2013

Helios marks strongly autoreactive CD4+ T cells in two major waves of thymic deletion distinguished by induction of PD-1 or NF-κB.

J Exp Med 2013 Feb 21;210(2):269-85. Epub 2013 Jan 21.

Department of Immunology, The John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory 0200, Australia.

Acquisition of self-tolerance in the thymus requires T cells to discriminate strong versus weak T cell receptor binding by self-peptide-MHC complexes. We find this discrimination is reported by expression of the transcription factor Helios, which is induced during negative selection but decreases during positive selection. Helios and the proapoptotic protein Bim were coinduced in 55% of nascent CCR7(-) CD4(+) CD69(+) thymocytes. These were short-lived cells that up-regulated PD-1 and down-regulated CD4 and CD8 during Bim-dependent apoptosis. Helios and Bim were also coinduced at the subsequent CCR7(+) CD4(+) CD69(+) CD8(-) stage, and this second wave of Bim-dependent negative selection involved 20% of nascent cells. Unlike CCR7(-) counterparts, Helios(+) CCR7(+) CD4(+) cells mount a concurrent Card11- and c-Rel-dependent activation response that opposes Bim-mediated apoptosis. This "hollow" activation response consists of many NF-κB target genes but lacks key growth mediators like IL-2 and Myc, and the thymocytes were not induced to proliferate. These findings identify Helios as the first marker known to diverge during positive and negative selection of thymocytes and reveal the extent, stage, and molecular nature of two distinct waves of clonal deletion in the normal thymus.
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http://dx.doi.org/10.1084/jem.20121458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3570102PMC
February 2013

Anti-islet autoantibodies trigger autoimmune diabetes in the presence of an increased frequency of islet-reactive CD4 T cells.

Diabetes 2011 Aug;60(8):2102-11

Department of Immunology, John Curtin School of Medical Research, Australian National University, Canberra, Australia.

Objective: To define cellular mechanisms by which B cells promote type 1 diabetes.

Research Design And Methods: The study measured islet-specific CD4 T cell regulation in T-cell receptor transgenic mice with elevated frequencies of CD4 T cells recognizing hen egg lysozyme (HEL) autoantigen expressed in islet β-cells and thymic epithelium under control of the insulin-gene promoter. The effects of a mutation in Roquin that dysregulates T follicular helper (Tfh) cells to promote B-cell activation and anti-islet autoantibodies were studied, as were the effects of HEL antigen-presenting B cells and passively transferred or maternally transmitted anti-islet HEL antibodies.

Results: Mouse anti-islet IgG antibodies-either formed as a consequence of excessive Tfh activity, maternally transmitted, or passively transferred-caused a breakdown of tolerance in islet-reactive CD4(+) cells and fast progression to diabetes. Progression to diabetes was ameliorated in the absence of B cells or when the B cells could not secrete islet-specific IgG. Anti-islet antibodies increased the survival of proliferating islet-reactive CD4(+) T cells. FcγR blockade delayed and reduced the incidence of autoimmune diabetes.

Conclusions: B cells can promote type 1 diabetes by secreting anti-islet autoantibodies that act in an FcγR-mediated manner to enhance the expansion of islet-reactive CD4 T cells and cooperate with inherited defects in thymic and peripheral CD4 T-cell tolerance. Cooperation between inherited variants affecting CD4 T-cell tolerance and anti-islet autoantibodies should be examined in epidemiological studies and in studies examining the efficacy of B-cell depletion.
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http://dx.doi.org/10.2337/db10-1344DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142068PMC
August 2011

T-cell regulation by casitas B-lineage lymphoma (Cblb) is a critical failsafe against autoimmune disease due to autoimmune regulator (Aire) deficiency.

Proc Natl Acad Sci U S A 2010 Aug 28;107(33):14709-14. Epub 2010 Jul 28.

Immune Tolerance and Signalling Laboratory, Department of Immunology, John Curtin School of Medical Research, Australian National University, Canberra 0200, Australia.

Autoimmune polyendocrinopathy syndrome type 1 (APS1) results from homozygous Aire mutations that cripple thymic deletion of organ-specific T cells. The clinical course in man and mouse is characterized by high variability both in the latent period before onset of autoimmune disease and in the specific organs affected, but the reasons for this are unknown. Here we test the hypothesis that the latent period reflects the failsafe action of discrete postthymic mechanisms for imposing self-tolerance in peripheral T cells. Aire-deficient mice were crossed with mice of a uniform major histocompatibility complex (MHC) haplotype and genetic background carrying specific genetic defects in one of four distinct peripheral tolerance mechanisms: activation-induced cell death (Fasl(gld/gld)), anergy and requirement for CD28 costimulation (Cblb(-/-)), inhibition of ICOS and T(FH) cells (Rc3h1(san/san)), or decreased numbers of Foxp3(+) T regulatory cells (Card11(unm/unm)). Cblb-deficiency was unique among these four in precipitating rapid clinical autoimmune disease when combined with Aire-deficiency, resulting in autoimmune exocrine pancreatitis with median age of survival of only 25 d. Massive lymphocytic infiltration selectively destroyed most of the exocrine acinar cells of the pancreas and submandibular salivary gland, and CD4(+) and CD8(+) subsets were necessary and sufficient to transfer the disease. Intrinsic regulation of peripheral T cells by CBL-B thus serves a uniquely critical role as a failsafe against clinical onset of autoimmune disease in AIRE deficiency, and multiple peripheral tolerance mechanisms may need to fail before onset of clinical autoimmunity to many organs.
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http://dx.doi.org/10.1073/pnas.1009209107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2930471PMC
August 2010

A key role for TGF-beta signaling to T cells in the long-term acceptance of allografts.

J Immunol 2007 Sep;179(6):3648-54

Therapeutic Immunology Group, Sir William Dunn School of Pathology, Oxford, United Kingdom.

TGF-beta is a key immunoregulatory cytokine which supports self-tolerance by signaling to T cells. In this report, we show a crucial role for TGF-beta signaling to T cells in enabling the long-term acceptance of allografts, whether natural or induced therapeutically by coreceptor and costimulation blockade. The requirement for TGF-beta appears most pronounced during the initial exposure to alloantigens. We demonstrate the ability of TGF-beta to direct the development in vitro of regulatory cells that suppress graft rejection in vivo. Such suppression was not affected by anti-TGF-beta treatment of the recipient mice. Despite this, TGF-beta may still have a role in CD4+ cell-mediated suppression of antiallograft responses in vivo, since its neutralization can, in some cases, abrogate suppression. These results show that TGF-beta signaling to T cells is dispensable for mounting destructive responses against skin allografts while appearing to be an essential intermediary in establishing long-term tolerance.
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http://dx.doi.org/10.4049/jimmunol.179.6.3648DOI Listing
September 2007