Mechanisms Of Immune Tolerance Research Articles

Gut Microbiota as a Target for Preventive and Therapeutic Intervention against Food Allergy.

The gut microbiota plays a pivotal role in immune system development and function. Modification in the gut microbiota composition (dysbiosis) early in life is a critical factor affecting the development of food allergy. Many environmental factors including caesarean delivery, lack of breast milk, drugs, antiseptic agents, and a low-fiber/high-fat diet can induce gut microbiota dysbiosis, and have been associated with the occurrence of food allergy. New technologies and experimental tools have provided information regarding the importance of select bacteria on immune tolerance mechanisms. Short-chain fatty acids are crucial metabolic products of gut microbiota responsible for many protective effects against food allergy. These compounds are involved in epigenetic regulation of the immune system. These evidences provide a foundation for developing innovative strategies to prevent and treat food allergy. Here, we present an overview on the potential role of gut microbiota as the target of intervention against food allergy.

Immune Tolerance Effect in Mesenteric Lymph Node Lymphocytes of Geniposide on Adjuvant Arthritis Rats.

Rheumatoid arthritis (RA) is a systemic, Th1 cytokine-predominant autoimmune disease result in a chronic and inflammatory disorder. Geniposide (GE), an iridoid glycoside compound that is purified from Gardenia jasminoides Ellis, has antiinflammatory and other immunoregulatory effects, but its exact mechanism of actions on RA is unknown. The aim of this study was to elucidate antiinflammation effects of GE on adjuvant arthritis (AA) rats and its possible immune tolerance mechanisms. Male Sprague-Dawley rats were administered with GE (30, 60, and 120mg/kg) orally from day 17 to 24 after immunization. Lymphocyte proliferation was assessed by MTT. Levels of interleukin-2 (IL-2), IL-4, and transforming growth factor-β1 were tested by ELISA. The expression of β2-AR, GRK2, and β-arrestin-1 and β-arrestin-2 was detected by western blot. Geniposide was found to relieve the secondary hind paw swelling and arthritis scores, along with attenuating histopathologic changes and decreasing IL-2 and increasing IL-4, transforming growth factor-β1 in mesenteric lymph node (MLN) lymphocytes of AA rats. In addition, GE in vivo increased the expression of β2-AR and decreased the expression of GRK2, β-arrestin-1 and β-arrestin-2, and level of cyclic adenosine monophosphate of MLN lymphocytes in AA rats. From these results, we can infer that GE on immune tolerance effects, β2-AR desensitization, and β2-AR-AC-cyclic adenosine monophosphate transmembrane signal transduction of MLN lymphocytes plays crucial roles in antiinflammatory and immunoregulatory pathogeneses of RA. Copyright © 2017 John Wiley & Sons, Ltd.

Immune Tolerance of Mesenchymal Stem Cells and Induction of Skin Allograft Tolerance.

Mesenchymal stem cells not only possess reparative properties, but also have immunomodulatory effect. Owing to the properties, they have been proposed to be hopeful candidates for cell therapy in the process of organ transplantation. In the preclinical researches, it shows that MSCs is capable of prolonging graft survival and inducing tolerance in some cases. Various mechanisms of immune tolerance were reported before, such as tolerogenic dendritic cells, induction of apoptosis, regulatory T cells, mixed chimerism, soluble factors and anergy. Furthermore, the induction of immune tolerance may be influenced by the dose, route and optimal timing of MSCs administration. Allograft of skin can provisionally restore the function of skin barrier and offer a good environment to expand micro-skin auto-graft; however, at the same time, it can cause strong immune rejection, which leads to the failure of skin graft. The review aims at analyzing the mechanisms of immunosuppression mediated by MSCs, and the induction of tolerance of skin graft by MSCs. Mesenchymal stem cells are hopeful candidates for cell therapy in the process of organ transplantation, and can induce immune tolerance of skin graft to some extent.

Increased levels of soluble HLA-G molecules in Tunisian patients with chronic hepatitis B infection.

Hepatitis B virus (HBV) infection is a global health problem. The mechanisms of immune tolerance in HBV infection are still unclear. The host immune response plays a critical role in determining the outcome of HBV infection. Human leucocyte antigen-G (HLA-G) is involved in immunotolerogenic process and infectious diseases. This study aimed to explore the implication of soluble HLA-G (sHLA-G) and its isoforms in HBV infection. Total sHLA-G (including shedding HLA-G1 and HLA-G5) was analysed by ELISA in 95 chronic HBV patients, 83 spontaneously resolvers and 100 healthy controls (HC). To explore the presence of sHLA-G dimers, we performed an immunoprecipitation and a Western blot analysis on positive samples for sHLA-G in ELISA. The serum levels of sHLA-G were significantly increased in patients with chronic HBV patients compared to spontaneously resolvers and HC (P<.0001). Interestingly, we found an increased level of sHLA-G1 in chronic HBV patients than in spontaneously resolvers and HC (P<.001). In addition, the expression of HLA-G5 seems to be higher in the sera of chronic HBV patients than spontaneously resolvers (P=.026). The analysis of HLA-G dimers showed the presence of homodimers in 93% of chronic HBV patients, 67% in spontaneously resolvers and 60% in HC. These results provide evidence that sHLA-G may have a crucial role in the outcome of HBV infection and could be proposed as a biomarker for infection outcome. Based on its tolerogenic function, HLA-G might be considered as a new promising immunotherapeutic approach to treat the chronic infection with HBV.

Brief report: Decreased expression of CD244 (SLAMF4) on monocytes and platelets in patients with systemic lupus erythematosus

The signalling lymphocyte activation molecule (SLAM) family receptors play important roles in modulating immune responses. Previous studies in murine models and patients have suggested an association of the SLAM family (SLAMF) members with the development of autoimmunity, particularly systemic lupus erythematosus (SLE). Since previous investigations on CD244 expression have focussed on NK and T cells, the aim of this study was to evaluate the surface expression of major SLAMF members across monocytes and polymorphonuclear cells in an Asian SLE cohort and explore their potential associations with SLE-related disease activity and autoantibodies. Thirty-nine SLE patients and twenty-nine healthy controls (HC) were evaluated for the expression of CD150, CD84, CD229, CD48, CD244, CD352 and CD319. We determined a significantly lower expression of CD244 on monocytes in SLE patients compared to HC. Furthermore, monocyte CD244 expression was negatively associated with several serum autoantibody titres. Our findings suggest that this molecule plays an important role in immune tolerance mechanisms and should be investigated further.

Mechanisms of tolerance and potential therapeutic interventions in Alopecia Areata.

This review aims to address the mechanisms of compromised immune tolerance contributing to the development and maintenance of Alopecia Areata (AA). Our goal is to also highlight future treatment opportunities and therapeutics that will safely and efficiently restore hair growth and maintain patients in remission. AA is a presumptive autoimmune disorder that coincides and genetically clusters to several other autoimmune diseases. In this review, we pay attention to the learnings from the mechanistic research and drug development in these other autoimmune conditions. Interestingly, most of these diseases have been linked to compromised central and peripheral tolerance, and increased intestinal inflammation with enhanced gut permeability. Break of tolerance and priming of the autoreactive T-cells to attack antigenic epitopes in the hair follicle most likely requires several steps which include escape from negative selection and compromised peripheral tolerance. Local skin-related changes are also of importance due to the patchy manifestation of the skin areas with loss of hair, particularly in the early disease. Here, we discuss the defective mechanisms of tolerance, both central and peripheral, and hypothesize that the disease is driven by areas of tolerance break, and that these could be targeted for successful therapeutic interventions.

Clonal Deletion and Anergy Play Dominant Role To Achieve Immune Tolerance After Reduced Intensity Unrelated Donor Cord Blood Transplantation (UCBT)

Abstract The mechanism of immune tolerance after successful hematopoietic stem cell transplantation is not fully understood. Both central (clonal deletion) and peripheral (anergy, Treg, Tr1) mechanisms are conceivable and may even coexist. In this study, we set up serial experiments to test for the presence and relative contribution of these mechanisms after HLA-mismatched UCBT in the GvH direction. Nine patients (age 1m to 9y) were transplanted and enrolled on a clinical trial (NCT01852370). Five immunocompetent patients were off immunosuppression therapy (IST) with no GVHD, while 4 had either limited or recently resolved GvHD and were still on IST when studied. Donor T cell chimerism was a median 97%. Purified T cells responses to host APCs were measured by MLR (3HTdR) and CTL reaction (Europium assay), along with cytokine secretion profiling (Bioplex). Host-reactive T cell clones were tracked with TCRVβ repertoire by ImmunoSEQ® (Adaptive Biotech). In tolerant patients, there was no significant MLR or CTL response towards host APC. Similarly, cytokine profiles revealed non-responsiveness while T cells responded vigorously to 3rd party APC by all assays. Recipient-specific T cell clones that were identified from infused UCB stimulated by host APC pre-UCBT became undetectable. There was no indication of Treg or Tr1 cell involvement in sustaining tolerance as deletion by IL-2 immunotoxin or IL-10R blockade was unable to “break” tolerance. However, low dose IL-2 (5U/mL) was able to restore some proliferation (S.I.=19; p=0.05) and IL-13, IFNγ, TNFα secretion, but in lesser degree in comparison to 3rd party responses (S.I.=112). In summary, clonal deletion and anergy contribute to immune tolerance after UCBT with deletion being dominant.

Liver sinusoidal endothelial cells regulate adaptive immune tolerance in the liver

Liver sinusoidal endothelial cells are a major group of nonparenchymal cells in the liver and are involved in immunological surveillance of the liver through the expression of various scavenger receptors and pattern recognition receptors. However, in case of several physiological states, viral infections, and tumor environment, liver sinusoidal endothelial cells maintain immune tolerance in the liver through various mechanisms and cause persistent viral infection and tumor metastasis. This article reviews the mechanisms of immune tolerance of CD4 + T cells and CD8 + T cells in the liver induced by liver sinusoidal endothelial cells.

The Linkage Between Inflammation and Immune Tolerance: Interfering with Inflammation in Cancer.

It is widely accepted that chronic inflammation critically contributes to cancer. Immune tolerance in cancer mediates tumor escape from the immune system. The mechanisms of relations between inflammation and immune tolerance are still not fully elucidated. The main mechanisms that link inflammation and tolerance are considered. Drug targets that are in use to interfere with inflammation in cancer are discussed. Inflammation mediates tumor-induced tolerance. The induction and the maintenance of the chronic inflammatory response is a universal mechanism of immune tolerance.

The Balance between CD8+ T Cell-Mediated Clearance of AAV-Encoded Antigen in the Liver and Tolerance Is Dependent on the Vector Dose

The liver continuously receives antigens from circulation and the gastrointestinal tract. A complex immune regulatory system has evolved in order to both limit inflammation and promote tolerance in the liver. Although insitu immune tolerance mechanisms enable successful gene therapy and liver transplantation, at the same time they facilitate chronic infections by pathogens such as hepatitis viruses. It is, however, poorly understood why hepatocytes infected with hepatitis viruses or transduced with adeno-associated virus (AAV)-based vectors may be rejected by CD8+ Tcells several months later. We found that hepatic transfer of limited doses of an AAV-ovalbumin vector rapidly induced antigen-specific CD8+ Tcells that only became functionally competent after >2months. At this time, CD8+ Tcells had downregulated negative checkpoint markers, e.g., the programmed death 1 [PD-1] receptor, and upregulated expression of relevant cytokines. At further reduced vector dose, only intrahepatic rather than systemic CD8+ Tcell responses occurred, showing identical delay in antigen clearance. In contrast, PD-1-deficient mice rapidly cleared ovalbumin. Interestingly, higher vector dose directed sustained transgene expression without CD8+ Tcell responses. Regulatory Tcells, IL-10 expression, and Fas-L contributed to high-dose tolerance. Thus, viral vector doses profoundly impact CD8+ Tcell responses.

The study of bone mesenchymal stem cells combined with interleukin-6 monoclonal antibody induce immune tolerance of rat heart transplantation

Objective To search for the effect and mechanism of immune tolerance that bone mesenchymal stem cells (MSCs) and Interleukin-6 monoclonal antibody (IL-6 mAb) affect rat heart transplantation. Methods Donor (SD rats) and receptor (Wistar rats) of 20 were randomly divided into four groups, GroupⅠ: The heart from SD rat was transplanted into the abdomen of Wistar rat. GroupⅡ: receptors of Wistar rats were injected normal saline daily 0.2 ml before surgery for five consecutive days and after heart transplantation for 3 days via jugular vein. Group Ⅲ: receptor was injected mesenchymal stem cells 1×106/0.2 ml before surgery for five consecutive days and after heart transplantation for 3 days via jugular vein. Group Ⅳ: receptor Wistar rat were injected MSCs and IL-6 mAb [100 μg/(kg·d)] before surgery for five consecutive days and after heart transplantation for 3 days via jugular vein. Testing Items: cardiac allograft survival time, donor heart pathological changes, receptor of CD4+ CD25+ regulatory T (Treg)cell change, T helper cell 17 (Th17) ’ s change, the expression of forkhead box P3 (FoxP3) protein in the Treg cells and serum transforming growth factor-beta1 (TGF-β1), Interleukin-10 (IL-10), Interleukin-2 (IL-2), Interleukin-6 (IL-6), Interleukin-17 (IL-17) change. Results The average survival time of group Ⅳ [(40.800±8.815) d] was longer than other groups [Ⅰ: (7.600±1.140) d; Ⅱ: (8.600±1.817) d; Ⅲ: (21.800±1.304) d]; The peripheral blood CD4+ CD25+ Treg [Ⅰ: (4.70±0.15)%; Ⅱ: (4.90±0.40)%; Ⅲ: (11.22±0.28)%; Ⅳ: (21.40±0.62))%], FoxP3 protein expression rate [Ⅰ: (71.21±1.05)%; Ⅱ: (71.07±1.41)%; Ⅲ: (72.69±3.84)%; Ⅳ: (96.24±1.42)%], TGF-β1 [Ⅰ: (165.52±8.68) pg/ml; Ⅱ: (169.73±3.45) pg/ml; Ⅲ: (339.38±13.40) pg/ml; Ⅳ: (475.79±10.11) pg/ml], IL-10 [Ⅰ: (29.03±1.05) pg/ml; Ⅱ: (30.40±1.63) pg/ml; Ⅲ: (88.65±1.84) pg/ml; Ⅳ: (136.14±2.32) pg/ml] of Group Ⅲ and group Ⅳwere significantly higher than groupⅠand group Ⅱ and Group Ⅳ was higher than group Ⅲ; The peripheral blood th17 cell ratio [Ⅰ: (7.18±0.48)%; Ⅱ: (6.98±0.61)%; Ⅲ: (4.16±0.23)%; Ⅳ: (1.28±0.19)%], IL-2 [Ⅰ: (112.94±3.52) pg/ml; Ⅱ: (111.48±2.71) pg/ml; Ⅲ: (66.96±1.04) pg/ml; Ⅳ: (33.31±1.41) pg/ml], IL-6 [Ⅰ: (70.96±1.20) pg/ml; Ⅱ: (70.06±2.10) pg/ml; Ⅲ: (42.94±2.14) pg/ml; Ⅳ: (16.57±1.05) pg/ml], IL-17 [Ⅰ: (96.86±1.15) pg/ml; Ⅱ: (92.72±4.91) pg/ml; Ⅲ: (49.49±1.63) pg/ml; Ⅳ: (21.22±0.82) pg/ml] of Group Ⅲ and group Ⅳwere significantly lower than groupⅠand group Ⅱ and group IV is lower than group Ⅲ. Conclusion Bone mesenchymal stem cells and IL-6 mAb can significantly increase the receptors’ proportion of CD4+ CD25+ FoxP3+ Treg cells, reduce the proportion of Th17 cells, lower down IL-2, IL-17, IL-10, increase the expression of of TGF-β1 immune factors. So they can significantly extend the survival time of rats heart of transplantation. Key words: Mesenchymal stem cells; Interleukin-6 monoclonal antibody; Cardiac transplantation; Immunotolerance

Dendritic cell expression of the signaling molecule TRAF6 is required for immune tolerance in the lung.

Immune tolerance in the lung is important for preventing hypersensitivity, such as allergic asthma. Maintenance of tolerance in the lung is established by coordinated activities of poorly understood cellular and molecular mechanisms, including participation of dendritic cells (DCs). We have previously identified DC expression of the signaling molecule TRAF6 as a non-redundant requirement for the maintenance of immune tolerance in the small intestine of mice. Because mucosal tissues share similarities in how they interact with exogenous antigens, we examined the role of DC-expressed TRAF6 in the lung. As with the intestine, we found that the absence TRAF6 expression by DCs led to spontaneous generation of Th2-associated immune responses and increased susceptibility to model antigen-induced asthma. To examine the role of commensal microbiota, mice deficient in TRAF6 in DCs were treated with broad-spectrum antibiotics and/or re-derived on a germ-free (GF) background. Interestingly, we found that antibiotics-treated specific pathogen-free, but not GF, mice showed restored immune tolerance in the absence of DC-expressed TRAF6. We further found that antibiotics mediate microbiota-independent effects on lung T cells to promote immune tolerance in the lung. This work provides both a novel tool for studying immune tolerance in the lung and an advance in our conceptual understanding of potentially common molecular mechanisms of immune tolerance in both the intestine and the lung.

Effect of a synbiotic containing Lactobacillus rhamnosus GG and fructooligosaccharides on the dynamics of the level of fecal calprotectin in children of first year of life

Rationale: As clinical efficacy of probiotics and prebiotics is determined by their joint effects both on the mechanism of immune tolerance, gut inflammation and intestinal wall permeability, one of the objective methods to assess efficacy of probiotic strain-containing agents could be based on measurement of fecal calprotectin levels. Aim: To evaluate changes in fecal calprotectin as an efficacy parameter of treatment with the Lactobacillus rhamnosus GG – fructooligosacсharide complex for prevention of atopic dermatitis in infants. Materials and methods: Sixty healthy newborns from the risk group for allergic disorders were randomized (envelope randomization) into two groups: the infants from the control group (n = 31) were given widely used recommendations to prevent atopic dermatitis, whereas the infants from the study group (n = 29) were additionally administered a synbiotic containing Lactobacillus rhamnosus GG with fructooligosaccharides. The efficacy of the synbiotic therapy was assessed by measurement of fecal calprotectin levels at 3 and 6 months of the follow-up. Results: The first measurement of fecal calprotectin levels at 3 months showed its significant increase in all infants (mean 276.9 ± 128.8 mcg/G), compared to the normal range (below 50 mcg/G). The second measurement at 6 months demonstrated a decrease in fecal calprotectin in infants from both groups (mean 75.8 ± 55.3 mcg/G). However, mean levels of fecal calprotectin in the infants from the study group who had been administered the synbiotic, was significantly lower than that in the control group (48.6 ± 38.5 and 99.7 ± 57.4 mcg/G, respectively; р &lt; 0.05). Conclusion: The observed changes in fecal calprotectin levels support the positive role of synbiotics and lyophilized complex of Lactobacillus rhamnosus GG with fructooligosaccharides in the growth of gut microbiota in infants and in the reduction of inflammation, all of this being an important prerequisite for development of the oral tolerance mechanisms.

Immune Tolerance of Human Dental Pulp-Derived Mesenchymal Stem Cells Mediated by CD4⁺CD25⁺FoxP3⁺ Regulatory T-Cells and Induced by TGF-β1 and IL-10.

PurposeMost studies on immune tolerance of mesenchymal stem cells (MSCs) have been performed using MSCs derived from bone marrow, cord blood, or adipose tissue. MSCs also exist in the craniofacial area, specifically in teeth. The purpose of this study was to evaluate the mechanisms of immune tolerance of dental pulp-derived MSC (DP-MSC) in vitro and in vivo.Materials and MethodsWe isolated DP-MSCs from human dental pulp and co-cultured them with CD4+ T-cells. To evaluate the role of cytokines, we blocked TGF-β and IL-10, separately and together, in co-cultured DP-MSCs and CD4+ T-cells. We analyzed CD25 and FoxP3 to identify regulatory T-cells (Tregs) by fluorescence-activated cell sorting (FACS) and real-time PCR. We performed alloskin grafts with and without DP-MSC injection in mice. We performed mixed lymphocyte reactions (MLRs) to check immune tolerance.ResultsCo-culture of CD4+ T-cells with DP-MSCs increased the number of CD4+CD25+FoxP3+ Tregs (p<0.01). TGF-β or/and IL-10 blocking suppressed Treg induction in co-cultured cells (p<0.05). TGF-β1 mRNA levels were higher in co-cultured DP-MSCs and in co-cultured CD4+ T-cells than in the respective monocultured cells. However, IL-10 mRNA levels were not different. There was no difference in alloskin graft survival rate and area between the DP-MSC injection group and the non-injection group. Nonetheless, MLR was reduced in the DP-MSC injected group (p<0.05).ConclusionDP-MSCs can modulate immune tolerance by increasing CD4+CD25+FoxP3+ Tregs. TGF-β1 and IL-10 are factors in the immune-tolerance mechanism. Pure DP-MSC therapy may not be an effective treatment for rejection, although it may module immune tolerance in vivo.

Tryptophan Catabolism and Cancer Immunotherapy Targeting IDO Mediated Immune Suppression.

Over the last decade, tryptophan catabolism has been firmly established as a powerful mechanism of innate and adaptive immune tolerance. The catabolism of tryptophan is a central pathway maintaining homeostasis by preventing autoimmunity or immunopathology that would result from uncontrolled and overreacting immune responses. This is driven by the key and rate-limiting enzymes indoleamine-2,3-dioxygenase 1 (IDO1) and tryptophan-2,3-dioxygenase 2 (TDO), resulting in local depletion of tryptophan, while tryptophan catabolites accumulate, including kynurenine and its derivatives, depending on the presence of downstream enzymes in the kynurenine pathway. These metabolic modifications result in a local microenvironment that is profoundly immunosuppressive, as a result of various mechanisms whose respective role remains incompletely characterized. Drugs targeting this pathway, specifically IDO1, are already in clinical trials with the aim at reverting cancer-induced immunosuppression. Recent studies have demonstrated favorable pharmacokinetics profiles for first-generation (Indoximod NLG8189) and second-generation IDO1 inhibitors (INCB024360 and NLG919). Targeting tryptophan catabolism in combination with additional methods of therapy may improve efficacy of cancer immunotherapy. These methods include, but are not limited to vaccination, adoptive cellular therapy, checkpoint inhibitor blockade, and cyclooxygenase-2 (COX2) inhibition. Over the last decade, there has been a considerable increase in our understanding of the regulation and downstream mediators of tryptophan metabolism. This detailed understanding will expand opportunities to interfere with the pathway therapeutically on multiple levels. The object of this chapter is to highlight current and past key findings that implicate tryptophan catabolism as an important mediator of cancer immunity and discuss the development of multiple therapeutic targets.

Childhood food allergies: An evolutionary mismatch hypothesis.

For hominins living in the Paleolithic era, early food antigen exposures—in utero and throughout infancy—closely matched later exposures, and therefore immune system tolerance mechanisms evolved under the expectation of this condition being met. This predicts that the degree of mismatch between early and downstream food antigen exposures is a key variable underlying the development of childhood food allergies. Three historical periods are identified in which the degree of mismatch climbs from near zero to substantial, as we transition from one period to another. The first encompasses our long history as foragers; the second begins with the advent of farming and the third spans only the most recent two or three decades, and manifests from social changes driven largely by an explosion in access to information. Testable predictions are generated and evaluated in light of available evidence, and an approach for primary prevention of childhood food allergies is proposed.

Human Ig knockin mice to study the development and regulation of HIV-1 broadly neutralizing antibodies.

A major challenge for HIV-1 vaccine research is developing a successful immunization approach for inducing broadly neutralizing antibodies (bnAbs). A key shortcoming in meeting this challenge has been the lack of animal models capable of identifying impediments limiting bnAb induction and ranking vaccine strategies for their ability to promote bnAb development. Since 2010, immunoglobulin knockin (KI) technology, involving inserting functional rearranged human variable exons into the mouse IgH and IgL loci has been used to express bnAbs in mice. This approach has allowed immune tolerance mechanisms limiting bnAb production to be elucidated and strategies to overcome such limitations to be evaluated. From these studies, along with the wealth of knowledge afforded by analyses of recombinant Ig-based bnAb structures, it became apparent that key functional features of bnAbs often are problematic for their elicitation in mice by classic vaccine paradigms, necessitating more iterative testing of new vaccine concepts. In this regard, bnAb KI models expressing deduced precursor V(D)J rearrangements of mature bnAbs or unrearranged germline V, D, J segments (that can be assembled into variable region exons that encode bnAb precursors), have been engineered to evaluate novel immunogens/regimens for effectiveness in driving bnAb responses. One promising approach emerging from such studies is the ability of sequentially administered, modified immunogens (designed to bind progressively more mature bnAb precursors) to initiate affinity maturation. Here, we review insights gained from bnAb KI studies regarding the regulation and induction of bnAbs, and discuss new Ig KI methodologies to manipulate the production and/or expression of bnAbs in vivo, to further facilitate vaccine-guided bnAb induction studies.

LPS-treated bone marrow-derived dendritic cells induce immune tolerance through modulating differentiation of CD4+ regulatory T cell subpopulations mediated by 3G11 and CD127.

Intravenous transfer of LPS-treated bone marrow-derived dendritic cells blocks development of autoimmunity induced by CD4+ T cells in vivo. However, cellular mechanisms of dendritic cell-mediated immune tolerance have not yet been fully elucidated. Here, we report that there are two new subpopulations of CD4+CD25+FoxP3+GITR+ regulatory T cells (CD127+3G11+ and CD127+3G11- cells). LPS-treated dendritic cells facilitate development of CD4+CD127+3G11- regulatory T cells but inhibit that of CD4+CD127+3G11+ regulatory T cells. LPS-induced tolerogenic dendritic cells may cause immune tolerance through modulating balance of different subsets of CD4+ regulatory T cells mediated by CD127 and 3G11. Our results imply a new potential cellular mechanism of dendritic cell-mediated immune tolerance.

Circulating CD2 Negative T Cells in Pediatric Acute Leukemia

Introduction: Leukemia cells are able to escape from immunosurveillance using immune tolerance mechanisms as the majority of leukemia antigens are either shared or aberrantly expressed self-proteins. T cells reactive to these antigens are purged during thymic selection. CD2, a pan-T-cell antigen, is expressed early during T cell developments in thymus and is found on all subsets of mature T cells. Recent studies show that there are low levels of extrathymic CD2 negative (CD2-) T cells, which show immature T cell features and can be induced to differentiate into mature helper and cytotoxic T cells in vitro. Since circulating CD2- T cells could represent pre-selection immature T cells, they may play an important role in tumor immunity.Methods: 81 pediatric B-cell acute lymphoblastic leukemia (B-ALL) patients, 22 pediatric acute myeloid leukemia (AML) patients and 22 normal controls were included in this study. B-ALL group included 45 NCI-standard risk (SR) patients and 36 NCI-high risk patients. All the leukemia patients were diagnosed at Children's Mercy Hospital in the past ten years with a diagnostic peripheral blood (PB) specimen. The PB specimens were studied by four-color multiparameter flow cytometry with antibodies for T cell markers (CD2, CD3, CD4, CD5, CD7 and CD8) and CD45, and analyzed by BD FACSDiva 8.0.1. CD2- and CD3+ T cells were recorded as % of total T cells. Student's t-test was used to compare results.Results: The percentages of CD2- T cells in AML (mean ± STD: 1.31% ± 1.41%) and B-ALL (0.84% ± 0.67%) were significantly higher than that seen in control group (0.51% ± 0.52%, p<0.05). No significant difference was found between AML and B-ALL. There was no significant difference between HR B-ALL (0.96% ± 0.81%) and SR B-ALL (0.74% ± 0.52%). Interestingly, CD2- T cells in 4/5 B-ALLs with 11q23 (KMT2A) rearrangement were undetectable. All 3 therapy-related AML patients studied had KMT2A gene rearrangement, and had no detectable CD2- T cells with poor clinical outcome (overall survival less than 1 year). The 3 AMLs associated with Down syndrome, a prognostically favorable AML group, showed relative high levels (≥ 1.49%) of CD2- T cells.Conclusions: Circulating CD2- T cells are increased in peripheral blood in pediatric AML and B-ALL patients. KMT2A gene rearrangement, an unfavorable cytogenetic abnormality, is associated with a decrease in CD2- T cells. The relationship of KMT2A gene rearrangement and decrease in circulating CD2- T-cells as well as the relationship of CD2- T cells to clinical outcome should be evaluated in future studies. The role of CD2- T cells in tumor specific immunomodulation should be explored, and may impact future studies of cell-based cancer immunotherapeutics. DisclosuresNo relevant conflicts of interest to declare.

CD8αα+MHC Class II+ Cell with the Capacity To Terminate Autoimmune Inflammation Is a Novel Antigen-Presenting NK-like Cell in Rats.

Discovery of immune tolerance mechanisms, which inhibit pre-existing autoimmune inflammation, may provide us with new strategies for treating autoimmune diseases. We have identified a CD8αα+MHC class II+ cell with professional APC capacity during our investigation on spontaneous recovery from autoimmune glomerulonephritis in a rat model. This cell actively invades inflamed target tissue and further terminates an ongoing autoimmune inflammation by selective killing of effector autoreactive T cells. In this study, we show that this cell used a cytotoxic machinery of Ly49s+ NK cells in killing of target T cells. Thus, this CD8αα+MHC class II+ cell was a dually functional Ag-presenting NK-like (AP-NK) cell. Following its coupling with target T cells through Ag presentation, killing stimulatory receptor Ly49s6 and coreceptor CD8αα on this cell used rat nonclassic MHC class I C/E16 on the target T cells as a ligand to initiate killing. Thus, activated effector T cells with elevated expression of rat nonclassic MHC class I C/E16 were highly susceptible to the killing by the CD8αα+ AP-NK cell. Granule cytolytic perforin/granzyme C from this cell subsequently mediated cytotoxicity. Thus, inhibition of granzyme C effectively attenuated the killing. As it can recognize and eliminate effector autoreactive T cells in the inflamed target tissue, the CD8αα+ AP-NK cell not only represents a new type of immune cell involved in immune tolerance, but it also is a potential candidate for developing a cell-based therapy for pre-existing autoimmune diseases.