Emerging Roles on Immunological Effect of Indoleamine 2,3-Dioxygenase in Liver Injuries

Indoleamine 2,3-dioxygenase (IDO) is one of the initial rate-limiting enzymes of the kynurenine pathway (KP), which causes immune suppression and induction of T cell anergy. It is associated with the imbalance of immune homeostasis in numerous diseases including cancer, chronic viral infection, allergy, and autoimmune diseases. Recently, IDO has extended its role to liver field. In this review, we summarize the dysregulation and potentials of IDO in the emerging field of liver injuries, as well as current challenges for IDO targets. In particular, we discuss unexpected conclusions against previous work published. IDO is induced by pro-inflammatory cytokines in liver dysfunction and exerts an immunosuppressive effect, whereas the improvement of liver injury may require consideration of multiple factors besides IDO.

Superantigen Recognition and Interactions: Functions, Mechanisms and Applications

Superantigens are unconventional antigens which recognise immune receptors outside their usual recognition sites e.g. complementary determining regions (CDRs), to elicit a response within the target cell. T-cell superantigens crosslink T-cell receptors and MHC Class II molecules on antigen-presenting cells, leading to lymphocyte recruitment, induction of cytokine storms and T-cell anergy or apoptosis among many other effects. B-cell superantigens, on the other hand, bind immunoglobulins on B-cells, affecting opsonisation, IgG-mediated phagocytosis, and driving apoptosis. Here, through a review of the structural basis for recognition of immune receptors by superantigens, we show that their binding interfaces share specific physicochemical characteristics when compared with other protein-protein interaction complexes. Given that antibody-binding superantigens have been exploited extensively in industrial antibody purification, these observations could facilitate further protein engineering to optimize the use of superantigens in this and other areas of biotechnology.

Identification and Characterization of a Germline Mutation in CARD11 From a Chinese Case of B Cell Expansion With NF-κB and T Cell Anergy

B cell expansion with NF-κB and T cell anergy (BENTA) is a rare primary immunodeficiency disorder caused by gain-of-function (GOF) mutations in the CARD11 gene. Affected patients present with persistent B cell lymphocytosis in early childhood paired with lymphadenopathy and splenomegaly. Until now only six activating mutations from 14 patients have been reported in CARD11. Here we report a patient from China with polyclonal B cell lymphocytosis and frequent infections in early life. A heterozygous mutation (c.377G>A, G126D) in exon 5 of CARD11 gene (NM_032415) was identified by whole exome sequencing. In vitro functional studies showed that the G126D mutation is associated with increased expression of CARD11 and NF-κB activation in Hela cells. Flow cytometry analysis indicated NK cell activity and CD107a degranulation of the patient were decreased. RNA sequencing analysis showed that a number of genes in NF-κB pathway increased while those involved in NK cell activity and degranulation were down-regulated. In summary, our work identified a de novo germline GOF mutation in CARD11 with functional evidence of BENTA.

Superantigen Recognition and Interactions: Functions, Mechanisms and Applications

Superantigens are unconventional antigens which recognise immune receptors outside the usual binding sites e.g. complementary determining regions (CDRs), to elicit a response within the target cell. T-cell superantigens crosslink T-cell receptors and MHC Class II molecules on antigen-presenting cells, leading to lymphocyte recruitment, induction of cytokine storms and T-cell anergy or apoptosis among many other effects. B-cell superantigens, on the other hand, bind immunoglobulin receptors on B-cells affecting opsonisation, IgG-mediated phagocytosis, and drive B-cells into apoptosis. Here, through a review of the structural basis for recognition of immune receptors by superantigens, we show that their binding interfaces share specific physicochemical characteristics when compared with other protein-protein interaction complexes. Given that antibody-binding superantigens have been exploited extensively in industrial antibody purification, these observations could facilitate further protein engineering to optimize the use of superantigens in this and other areas of biotechnology.

Cbl-b deficiency prevents functional but not phenotypic T cell anergy

T cell anergy is an important peripheral tolerance mechanism. We studied how T cell anergy is established using an anergy model in which the Zap70 hypermorphic mutant W131A is coexpressed with the OTII TCR transgene (W131AOTII). Anergy was established in the periphery, not in the thymus. Contrary to enriched tolerance gene signatures and impaired TCR signaling in mature peripheral CD4 T cells, CD4SP thymocytes exhibited normal TCR signaling in W131AOTII mice. Importantly, the maintenance of T cell anergy in W131AOTII mice required antigen presentation via MHC-II. We investigated the functional importance of the inhibitory receptor PD-1 and the E3 ubiquitin ligases Cbl-b and Grail in this model. Deletion of each did not affect expression of phenotypic markers of anergic T cells or T reg numbers. However, deletion of Cbl-b, but not Grail or PD-1, in W131AOTII mice restored T cell responsiveness and signaling. Thus, Cbl-b plays an essential role in the establishment and/or maintenance of unresponsiveness in T cell anergy.

Abstract 16582: Costimulation Blockade With Anti Cd80 and Cd86 Monoclonal Antibodies Prolonged Graft Survival in Allogeneic Ips Cell-Derived Cardiomyocyte Patch Transplantation

Introduction: How to avoid immune rejection after transplantation should be elucidated for confirmed efficacy in clinical application of allogenic induced pluripotent stem cell derived cardiomyocyte patch. The blockade of CD28-CD80/86 costimulation is known to induce T cell anergy and immune tolerance by the recruitment of regulatory T cells (T reg) and prolong graft survival in organ transplantation. Hypothesis: We hypothesized that the blockade of CD28-CD80/CD86 costimulatory pathway by anti-CD80/CD86 monoclonal antibodies (mAbs) induces T cell anergy in vivo and suppresses immune rejection in allogeneic iPSC-CMs subcutaneous transplantation mice model. Methods: T cell anergy was induced in vitro by co-culture of Balb/c and 25Gy irradiated C57BL/6 splenocytes with anti-CD80/86 mAbs for 5 days. The inhibitory effect of anergic cells was evaluated by mixed lymphocyte reaction (MLR) in C57BL/6 and Balb/c splenocytes with anergic cells. IFN-g in MLR supernatants was measured by ELISAs to assess immune response. C57BL/6 iPSC-CMs expressing luciferase were subcutaneously transplanted into Balb/c. Anti-CD80/CD86 mAbs were injected intraperitoneally 250μg/dose on day 0, 1, and 2 (treated mice, n=6). In control mice (n=6), equivalent volume of saline was injected. To evaluate iPSC-CMs graft survival, photon counts of iPSC-CMs were measured by bioluminescence imaging system (BLI). Cells of harvested grafts were analyzed by immunofluorescence staining (IF). Results: On ELISAs, IFN-g in MLR supernatants co-cultured with anergic cells was significantly lower as compared with those without anergic cells (12.3±14.4 vs. 251±80.2 pg/ml, p=0.007). The ability to suppress the alloresponses was dose-dependent. BLI showed that photon counts on day 14 in treated mice were significantly higher than in control mice (7397±2651 vs. 2703±1271, p=0.003). IF showed a siginificantly higher ratio of CD4 and Foxp3 double positive cells to CD4-postive cells in the grafts on day 7 in treated mice as compared with in control mice (23±3% vs. 9±3%, p=0.009) Conclusions: The blockade of CD28-CD80/CD86 costimulatory pathway might suppress immune rejection in allogeneic iPSC-CMs transplantation mice model and T reg might involve this immune tolerance.

Self and microbiota-derived epitopes induce CD4+ T cell anergy and conversion into CD4+Foxp3+ regulatory cells

The physiological role of T cell anergy induction as a key mechanism supporting self-tolerance remains undefined, and natural antigens that induce anergy are largely unknown. In this report, we used TCR sequencing to show that the recruitment of CD4+CD44+Foxp3−CD73+FR4+ anergic (Tan) cells expands the CD4+Foxp3+ (Tregs) repertoire. Next, we report that blockade in peripherally-induced Tregs (pTregs) formation due to mutation in CNS1 region of Foxp3 or chronic exposure to a selecting self-peptide result in an accumulation of Tan cells. Finally, we show that microbial antigens from Akkermansia muciniphila commensal bacteria can induce anergy and drive conversion of naive CD4+CD44-Foxp3− T (Tn) cells to the Treg lineage. Overall, data presented here suggest that Tan induction helps the Treg repertoire to become optimally balanced to provide tolerance toward ubiquitous and microbiome-derived epitopes, improving host ability to avert systemic autoimmunity and intestinal inflammation.