Notch Is a Novel Critical Signaling Pathway Regulating Responses of T Cell and Antigen Presenting Cells in Multiple Murine aGVHD Models

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5418-5418
Author(s):  
Xiaodan Luo ◽  
Pengfei Qin ◽  
Chunyan Wang ◽  
Zhenqian Huang ◽  
Huo Tan
Keyword(s):  
T Cells ◽  
Body Weight ◽  
T Cell ◽  
Signaling Pathway ◽  
Antigen Presenting Cells ◽  
Hematopoietic Stem ◽  
Secretase Inhibitor ◽  
Donor T Cells ◽  
Antigen Presenting

Abstract Introduction: Acute graft-versus-host disease (aGVHD) is a potentially life-threatening complication mediated by both host-derived antigen presenting cells (APCs) and donor T cells after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Despite prophylaxis and treatments, aGVHD stell occurs in many allo-HSCT patients. The role of Notch1 signal inhibition becomes more and more important in aGVHD study. This study is to investigate the role of Notch1 inhibition by γ-secretase inhibitor DAPT in murine aGVHD model. Methods: We established a C57BL/6 BALB/c murine aGVHD model. γ-secretase inhibitor-DAPT is used to inhibit Notch1 signal in vivo and in vitro before transplantation. The degree of clinical and histopathologic GVHD is assessed by aGVHD scores and body weight. The functions of host-derived APCs and donor T cells are analyzed by flow cytometry, ELISA and PCR. Results: All mice survived at least 14 days after transplantation and all of them developed aGVHD (n=20). The expression of Hes-1, as one of the target genes of Notch1 signal pathway, decreased significantly after DAPT inhibition. Body weight of mice in control groups decreased significantly compared to mice with Notch1 inhibition by DAPT after transplantation. Notch1 inhibited recipients produced markedly decreased amounts of the pro-inflammatory cytokines IFN-γ. The expressions of CD4 and Foxp3 increased while CD11c, CD80 and CD86 decreased after Notch1 inhibition. Conclusions: These results indicate that Notch is a novel critical signaling pathway regulating responses of T cell and antigen presenting cells in multiple murine aGVHD models. Notch signaling inhibition appears to limit the harmful effects of aGVHD. Disclosures No relevant conflicts of interest to declare.

Graft-Versus-Host-Disease Recruits Both Monocyte and Pre-Conventional Dendritic Cell-Derived Tissue Antigen Presenting Cells Independent Of CCR2 and CCR6

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4463-4463
Author(s):  
Sarah Morin-Zorman ◽  
Christian Wysocki ◽  
Catherine Matte-Martone ◽  
Kathryn W Juchem ◽  
Hung Sheng Tan ◽  
...  
Keyword(s):  
T Cells ◽  
Graft Versus Host Disease ◽  
Antigen Presenting Cells ◽  
Blood Monocytes ◽  
Hematopoietic Stem ◽  
Host Disease ◽  
Graft Versus Host ◽  
Donor T Cells ◽  
Antigen Presenting

Graft-versus-host disease (GVHD) limits the broader application of allogeneic hematopoietic stem cell transplantation. In prior studies we defined roles for both host and donor-derived antigen presenting cells (APCs) in the activation of alloreactive donor T cells and in promotion of GVHD. While initial T cell activation in GVHD occurs predominantly in secondary lymphoid organs, we have consistently observed MHCII+ donor-derived APCs, including dendritic cells (DCs), in histopathologic GVHD lesions, frequently adjacent to infiltrating T cells, suggesting they have a role in local GVHD reactions. Donor-derived tissue APCs (t-APCs), including tissue-DCs (t-DCs) could activate donor T cells through indirect or cross-presentation of host antigens, produce chemokines that recruit other effectors, and elaborate inflammatory mediators or suppressors of inflammation. We first characterized t-DC subsets in the skin and bowel of GVHD-affected mice. 129 (H-2b) hosts were irradiated and reconstituted with B6 (H-2b) BM with or without CD4+ and CD8+ T cells to induce GVHD and analyzed mononuclear cells from skin and bowel approximately 4 weeks post transplant. In skin, both main dermal DC populations (CD11b+ and CD103+) were significantly increased in GVHD mice as compared to BM alone controls, though the ratios of CD11b+: CD103+ DCs were similar. In the bowel lamina propria, the ratios of CD11b+CD103- to CD11b+CD103+ were increased in GVHD mice in the colon but were similar to that in BM alone controls in the small bowel. We next studied the roles of CCR6 and CCR2 in the recruitment of donor-derived APCs to skin and bowel. We transplanted mice with CCR6-/- BM in competition with wild type (wt) BM and found that the contribution of each to skin and bowel APCs matched their contributions to myeloid hematopoiesis in BM, spleen and blood, indicating that CCR6 is not required. To study the role of CCR2 we first compared mice transplanted with either wt or CCR2-/- BM with wt T cells. Despite having a profound reduction in blood monocytes, all skin and bowel t-APC subsets were present in CCR2-/- recipients, indicating that CCR2 is not required for t-APC recruitment in contrast to its role in many other models of inflammation. However, CD103+ DCs were more prevalent relative to CD11b+ DCs, consistent with a pre-cDC origin. Despite monocytopenia, recipients of CCR2-/- BM developed clinical GVHD; histology data is being analyzed and will be presented. To better define the contributions of CCR2 to t-APC recruitment and to determine monocyte versus pre-cDC origin of t-DCs, we transplanted mice with CCR2-/- BM in competition with wt BM and compared ratios of BM and blood precursors (pre-cDCs and monocytes) to t-DC ratios. For CD103+ DCs, wt/KO ratios matched the ratios of general myeloid hematopoiesis and pre-cDCs, indicating a pre-cDC origin. For CD11b+CD103- DCs, the ratio of wt/KO matched that in blood monocytes. We further subsetted CD11b+ t-DCs based on the expression of Ly6C, MAR1, CD64 and CD24, used to differentiate pre-cDC from mono-derived DCs in other organs, and did not identify any population with wt/KO ratios that did not match that of the general CD11b+ DC population, suggesting that most if not all CD11b+ t-DCs are of monocyte origin. Experiments are underway examining the role of CX3CR1 in t-APC recruitment and these data will be presented. Disclosures: No relevant conflicts of interest to declare.

Abstract 252: Interleukin-27 Signaling Regulates Myeloid Cells Activation in Atherosclerosis

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Iuliia Peshkova ◽  
Aliia Fatkhullina ◽  
Ekaterina Koltsova
Keyword(s):  
T Cells ◽  
T Cell ◽  
Inflammatory Cytokines ◽  
Antigen Presenting Cells ◽  
Atherosclerotic Lesions ◽  
Mediators Of Inflammation ◽  
Antigen Presenting ◽  
Deficient Mice ◽  
Pro Inflammatory Cytokines

Atherosclerosis is a lipid-driven inflammatory disease characterized by the progressive plaque growth in the vessels. Cytokines are important mediators of inflammation and atherosclerosis. While pro-inflammatory cytokines were extensively investigated, little is known about the role of anti-inflammatory cytokines as to their ability to control vascular inflammation. We tested whether immunoregulatory IL-27R signaling is important to control inflammation in mouse models of atherosclerosis. We found that atherosclerosis-prone mice with hematopoietic deficiency of IL-27R ( Ldlr -/- mice reconstituted with bone marrow from Il27ra -/- ) or global deficiency ( Il27ra -/- x Apoe -/- ) developed significantly larger atherosclerotic lesions compared to controls. Atherosclerotic lesions in IL-27R deficient mice contained more CD45 + leukocytes and CD4 + T cells, which produced pro-atherogenic cytokines IL-17A and TNF-α. These cytokines normally suppressed by IL-27, regulated the expression of CCL2 and other chemokines, which in turn led to accumulation of myeloid CD11b + and CD11c + cells in atherosclerotic aortas. Using two-photon microscopy, we found enhanced interactions between antigen presenting cells and T cells in the aortas of IL-27R deficient mice accompanied by enhanced CD4 T cell proliferation. Moreover, macrophages in Il27ra -/- aortas also demonstrated enhanced ability to produce pro-inflammatory cytokines, including IL-1. The blockade of IL-1R signaling, however, strongly suppressed atherosclerosis progression in IL-27R deficient but not control mice, suggesting an important role of IL-27 in the regulation of IL-1 production in atherosclerosis. Overall, our data demonstrate that IL-27R signaling in atherosclerosis is required to control function of antigen presenting cells modulating subsequent T cell activation in the aortas. Moreover, it controls macrophage activation and pro-inflammatory myeloid cell-derived cytokine production. These mechanisms altogether curb pathogenic T cell lineage differentiation and, thus, atherosclerosis, suggesting potent anti-atherogenic role of IL-27.

A Crucial Role for Antigen Presenting Cells in Donor CD4+CD25+ Regulatory T Cell Mediated Suppression of Experimental Gvhd.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 688-688
Author(s):  
Isao Tawara ◽  
Tomomi Toubai ◽  
Chelsea Malter ◽  
Yaping Sun ◽  
Evelyn Nieves ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Conflicts Of Interest ◽  
Antigen Presenting Cells ◽  
Class Ii ◽  
Indoleamine 2 ◽  
Effector Phase ◽  
Antigen Presenting

Abstract Abstract 688 Several lines of evidence show that donor derived mature CD4+CD25+Foxp3+ regulatory T cells (Tregs) suppress experimental GVHD. The mechanism of GVHD suppression by donor Tregs is, however, not well understood. Recent observations have brought in a renewed focus on the role of professional antigen presenting cells (APCs) in the induction and maintenance of GVHD by alloreactive T cell effectors (Teffs). But the role of APCs in modulating the responses of Tregs after allogeneic BMT is not known. We first tested the requirement of host APCs in Treg mediated regulation of GVHD. We utilized a clinically relevant CD8+ T cell dependent MHC matched but miHA disparate C3H.SW (H-2b) → wild type (wt) or Class II deficient Abb (II-/-) B6 (H-2b) model of GVHD because host APCs and target tissues from the Abb animals do not express class II and as such donor CD4+CD25+ Tregs will not directly interact with the host tissues while alloreactive CD8+ T cells could still respond to miHA allo-antigens presented by the intact class I on host APCs. The recipient Abb (II-/-) and wt B6 animals were lethally irradiated and transplanted with 2 × 105 CD8+ T cells along with or without CD4+CD25+ Tregs at 1:2 ratio from either syngeneic B6 or allogeneic C3H.SW animals. The wt recipients that received Tregs showed significantly better survival compared with the wt animals that did not receive any Tregs (P< 0.01) while the class II-/- animals showed similar GVHD mortality regardless of Treg infusion (P>0.8). To confirm whether the lack of Treg mediated protection was only due to the absence of interaction with host type APCs and also to exclude the possibility of development of Tregs from the infused BM we thymectomized wt B6 animals and then generated [B6 B6] controls and the [Abb B6] chimeras. These chimeric animals were used as recipients in a second BMT and transplanted with CD8+ Teffs and Tregs from allogeneic C3H.SW mice. Tregs reduced GVHD mortality in the [B6 B6] (P<0.01) but not in the [Abb B6] animals (P>0.7). We next evaluated whether host APC expression of allo-antigens alone was sufficient for Treg mediated GVHD protection in the absence of class II expression on target tissues by generating [B6 B6] and [B6 Abb] chimeras and found that Tregs demonstrated equivalent GVHD protection even when the class II allo-antigens were expressed only on the host APCs. Mechanistic studies demonstrated that Tregs significantly inhibited the expansion of CD8+ Teffs on days +10 and 17 after BMT in the spleens of the WT recipients (P<0.05) but not in the class II-/- animals. However, infused Tregs demonstrated reduced expansion in the class II-/- animals only early after BMT (on day +10) but was equivalent at later time-point (days 17 and 29) to the WT recipients. We further determined the mechanisms by which host APCs might contribute to Treg mediated protection. To this end we used IL-10-/-, indoleamine 2, 3 dioxygenase (IDO)-/- deficient animals and generated [IL-10-/- B6] and [IDO-/- B6] animals as recipients. Tregs mitigated GVHD mortality regardless of the ability of the host APCs to express IL-10 or IDO. We next determined whether Tregs suppressed Teffs in their activation phase at the level of their interaction with host APCs or in the effector phase. C3H.SW CD8+ T cells were primed (both in vivo and ex vivo with B6 allo-antigens) and then infused into the [β2mg-/- B6] animals such that pre-activated CD8 Teffs would still be able to initiate GVHD without the need for host APCs for their activation. Infusion of donor Tregs into [β2mg-/- B6] animals that were transplanted with the pre-activated Teffs mitigated GVHD severity demonstrating that Tregs, once activated by host APCs, were capable of suppressing Teff cells in their effector phase. Collectively our data show (a) host APCs are critical (b) expression of allo-antigens on host target tissues is not obligatory (c) host derived IL-10 and IDO are not critical for Treg mediated GVHD protection and (d) Tregs can mitigate GVHD by suppressing alloreactive Teffs in the effector phase even after they have been activated. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Gas6 deficiency in recipient mice of allogeneic transplantation alleviates hepatic graft-versus-host disease

Blood ◽  
2010 ◽  
Vol 115 (16) ◽  
pp. 3390-3397 ◽  
Author(s):  
Laurent Burnier ◽  
François Saller ◽  
Linda Kadi ◽  
Anne C. Brisset ◽  
Rocco Sugamele ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Graft Versus Host Disease ◽  
Antigen Presenting Cells ◽  
Allogeneic Bone ◽  
Hematopoietic Stem ◽  
Host Disease ◽  
Graft Versus Host ◽  
Antigen Presenting

Abstract Growth arrest-specific gene 6 (Gas6) is expressed in antigen-presenting cells and endothelial cells (ECs) but not in T cells. When wild-type (WT) or Gas6−/− mice received allogeneic non–T cell–depleted bone marrow cells, hepatic graft-versus-host disease (GVHD) was alleviated in Gas6−/− recipients regardless of donor genotype, but not in WT recipients. T-cell infiltration was more prominent and diffuse in WT than in Gas6−/− recipients' liver. When mice received 0.5 × 106 allogeneic T cells with T cell–depleted allogeneic bone marrow, clinical signs indicated that GVHD was less severe in Gas6−/− than in WT recipients, as shown by a significant improvement of the survival and reduced liver GVHD. These data demonstrate that donor cells were not involved in the protection mechanism. In addition, lack of Gas6 in antigen-presenting cells did not affect WT or Gas6−/− T-cell proliferation. We therefore assessed the response of WT or Gas6−/− ECs to tumor necrosis factor-α. Lymphocyte transmigration was less extensive through Gas6−/− than WT ECs and was not accompanied by increases in adhesion molecule levels. Thus, the lack of Gas6 in ECs impaired donor T-cell transmigration into the liver, providing a rationale for considering Gas6 pathway as a potential nonimmunosuppressive target to minimize GVHD in patients receiving allogeneic hematopoietic stem cell transplantation.

scholarly journals Decay-accelerating factor regulates T-cell immunity in the context of inflammation by influencing costimulatory molecule expression on antigen-presenting cells

Blood ◽  
2011 ◽  
Vol 118 (4) ◽  
pp. 1008-1014 ◽  
Author(s):  
Chongyun Fang ◽  
Takashi Miwa ◽  
Wen-Chao Song
Keyword(s):  
T Cells ◽  
T Cell ◽  
Knockout Mice ◽  
Antigen Presenting Cells ◽  
T Cell Immunity ◽  
Decay Accelerating Factor ◽  
Cell Immunity ◽  
Complement Regulator ◽  
Antigen Presenting

Abstract Recent studies have indicated a role of complement in regulating T-cell immunity but the mechanism of action of complement in this process remains to be clarified. Here we studied mice deficient in decay-accelerating factor (DAF), a key membrane complement regulator whose deficiency led to increased complement-dependent T-cell immune responses in vivo. By crossing OT-II and OT-I T-cell receptor transgenic mice with DAF-knockout mice, we found that lack of DAF on T cells did not affect their responses to antigen stimulation. Similarly, lack of DAF on antigen-presenting cells (APCs) of naive mice did not alter their T-cell stimulating activity. In contrast, APCs from DAF-knockout mice treated with inflammatory stimuli were found to be more potent T-cell stimulators than cells from similarly treated wild-type mice. Acquisition of higher T-cell stimulating activity by APCs in challenged DAF-knockout mice required C3 and C5aR and was correlated with decreased surface PD-L1 and/or increased CD40 expression. These findings implied that DAF suppressed T-cell immunity as a complement regulator in the context of inflammation but did not play an intrinsic role on T cells or APCs. Collectively, our data suggest a systemic and indirect role of complement in T-cell immunity.

T-Bet Is Critical for the Development of Acute Graft-Versus-Host Disease By Regulating Hematopoietic Antigen Presenting Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 846-846
Author(s):  
Jianing Fu ◽  
Yongxia Wu ◽  
Hung Nguyen ◽  
Jessica Lauren Heinrichs ◽  
Steven Schutt ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Apoptosis ◽  
Cell Activation ◽  
T Cell Apoptosis ◽  
Donor T Cells ◽  
Ifn Γ ◽  
Antigen Presenting

Abstract Graft-versus-host disease (GVHD) remains to be a major obstacle for the efficacy and continuing success of allogeneic hematopoietic stem cell transplantation in the treatment of various malignant and non-malignant diseases. Activation of antigen presenting cells (APCs), both host and donor origin, plays a crucial role in priming alloreactive donor T cells to induce and intensify acute GVHD (aGVHD). Beyond its critical effects on T cells, the T-box transcription factor T-bet also regulates activity of APCs, including dendritic cells (DCs) and B cells. However, the effect and mechanism of T-bet in regulating APCs in the development of aGVHD has not been investigated. To evaluate the role of T-bet in modulating APC function and aGVHD development, we compared the severity of aGVHD in WT versus T-bet-/- recipients using several well-defined, clinically relevant murine models of allogeneic bone marrow transplantation (allo-BMT). We observed that T-bet-/- recipients developed much milder aGVHD than their WT counterparts, reflected by significantly higher rate of survival, lower clinical scores, and better donor BM-derived B- and T-cell reconstitution. In T-bet-/- recipients, donor T cells significantly reduced IFN-γ production, proliferation and migration, and caused less damage in aGVHD target organs, such as liver and gut. By using various BM chimeras as the recipients, we further observed that T-bet expressed on recipient hematopoietic APCs was primarily responsible for donor T-cell response and pathogenicity in causing aGVHD. Additionally, we evaluated the role of T-bet in donor APCs by transplanting WT or T-bet-/- BM together with WT T cells into lethally irradiated allogeneic recipients. We observed that recipients of T-bet-/- BM developed attenuated aGVHD compared with those of WT BM, suggesting that T-bet also contributes to the function of donor APCs in the induction of GVHD. Given DCs are the most potent hematopoietic APCs, we subsequently focused on recipient DCs. DCs in T-bet-/- recipient produced less IFN-γ, expressed higher levels of Trail, but not FasL or TNF, to induce significantly higher levels of apoptosis on donor T cells prior to their massive proliferation. To test whether Trail/DR5 interaction is responsible for the induction of donor T cell apoptosis and subsequent reduction of aGVHD in T-bet-/- recipients, we compared the ability of WT or DR5-/- T cells in inducing aGVHD in WT versus T-bet-/- recipients after allo-BMT. While WT T cells induced severe aGVHD in WT recipients, they failed to do in T-bet-/- recipients. In contrast, DR5-/- donor T cells were capable to induce severe aGVHD in the recipients regardless of T-bet expression. These data suggests that Trail/DR5 interaction is a major signaling pathway responsible for donor T-cell apoptosis induced by T-bet-/- APCs, through which alleviates the development of aGVHD. In conclusion, we demonstrate that T-bet up-regulates IFN-γ production and down-regulates Trail expression on recipient DCs, which promotes donor T-cell activation and mitigates T-cell apoptosis, respectively. Thus, T-bet plays a critical role in the development of aGVHD by regulating the activity of hematopoietic APCs, particularly DCs. Taken together with our previous findings, we propose that T-bet is a potential therapeutic target for the control of aGVHD through regulating T-cell activation and differentiation as well as APC functions. Disclosures No relevant conflicts of interest to declare.

A Panel of Artificial Antigen-Presenting Cells (AAPC) Expressing Prevalent HLA Alleles Permits Generation of Cytotoxic T Cells Specific for Both Subdominant and Dominant Viral Epitopes for Adoptive Therapy.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2589-2589 ◽  
Author(s):  
Aisha Hasan ◽  
Wouter J. Kollen ◽  
A. Selvakumar ◽  
D. Trivedi ◽  
M. Sadelain ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Peptide Pool ◽  
Antigen Presenting Cells ◽  
Cytotoxic T Cell ◽  
Cell Transplant ◽  
Adoptive Therapy ◽  
Hematopoietic Stem ◽  
Hla Alleles ◽  
Antigen Presenting

Abstract Adoptive transfer of antigen specific T cells can be effective in treating viral infections complicating allogeneic hematopoietic stem cell transplant (HSCT) recipients. However, in practice, generation of T cells is often limited by insufficient supply of autologous antigen presenting cells; therapeutic activity in HLA disparate patients may also be impaired if the immuno- dominant T cells generated are restricted by HLA alleles not shared by the host. AAPCs have theoretical advantages for T cell therapies in terms of sustained supply and capacity to selectively stimulate T cells restricted by HLA alleles shared by donor and host. However, to date, only AAPC systems expressing HLA A*0201 have been characterized. Accordingly, we established a panel of AAPC consisting of NIH 3T3 mouse fibroblast cells, each transduced to express β2- microglobulin and a prevalent HLA class-I allele, specifically HLA A*0201, A*0301, A*2402, B*0702, B*0801 or C*0401, as well as the human co-stimulatory molecules B7.1, LFA-3 and ICAM-1. Novel promotor sequences were introduced to secure stable high expression of the allele on the AAPCs. Sensitization of T cells from seropositive donors with AAPCs expressing each of these alleles (4-8 donors/allele), either loaded with overlapping 15-mer peptides spanning the CMVpp65 sequence or transduced to express the CMV pp65 protein, resulted in 12-35 fold expansions of CD8 + T cells exhibiting CMV pp65 epitope-specific, HLA restricted activity, as quantitated by peptide -HLA tetramer binding, epitope specific production of interferon gamma, and cytotoxic activity against peptide loaded or CMV infected targets. Although both peptide pool loaded and transduced AAPCs induce CMV pp65 epitope specific T cells, yields were higher when transduced AAPCs were employed. In studies of T-cells from 5 donors when sensitized with either peptide pool loaded autologous dendritic cells (DC) or HLA sharing AAPCs, sensitization with DC selectively induced T-cells specific for 1-2 immunodominant CMV pp65 epitopes. In contrast, while sensitization with a panel of peptide loaded or transduced AAPCs expressing shared HLA alleles elicited responses to the same dominant epitopes, we could also regularly generate comparable cytotoxic T cell responses to subdominant epitopes which were either not produced or only present at low frequencies in T cells sensitized with autologous DC. Thus, this panel of AAPCs stably expressing a series of HLA alleles which, in aggregate, are detected in 70% of the patients referred for HSCT, can be employed for rapid generation of CMV-pp65 specific T cells of desired HLA restriction for adoptive therapy.

A Novel Role of Histone Deacetylase 11 (HDAC11) in the Regulation of IL-10 Production and Immune Tolerance Mediated by Antigen-Presenting Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1330-1330
Author(s):  
Hongwei Wang ◽  
Fengdong Cheng ◽  
D. Nguyen ◽  
I. Suarez ◽  
K. Wright ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
T Cell ◽  
Histone Deacetylase ◽  
Immune Tolerance ◽  
Antigen Presenting Cells ◽  
Enhanced Production ◽  
Inflammatory Status ◽  
Antigen Presenting

Abstract Antigen-presenting cells (APC) can induce T-cell activation as well as T-cell tolerance. The induction of such a divergent outcomes is determined by the inflammatory status of the APC at the time of encounter with antigen specific T-cells. The molecular basis by which the APC regulate this critical decision of the immune system remain not well understood. Chromatin modification induced by acetylation/deacetylation of histones plays an important role in regulation of gene transcription, including genes involved in the inflammatory response. Histone deacetylases, a set of enzymes involved in histone modification are molecular targets for histone deacetylase inhibitors (HDI), novel compounds being evaluated as anticancer drugs. Interestingly, in addition to their antitumor properties, HDI have been also shown to modulate inflammatory responses. We evaluated therefore whether treatment with the hydroxamic acid analogue pan-HDAC inhibitor LAQ824 could influence the inflammatory status of the APC and their ability to determine CD4+ T-cell priming versus tolerance. In vitro treatment of APCs with LAQ824 resulted in enhanced acetylation of histones H-2A, H-2B, H3 and H4, increased expression of the co-stimulatory molecule B7.2 and enhanced production of pro-inflammatory mediators such as IL-1a, IL-1-b, IL-6, IL-12, TNF-a and RANTES in response to LPS stimulation. To our surprise, a dose-dependent inhibition of IL-10 mRNA and protein was observed in APCs treated with LPS and LAQ824. Chromatin immune precipitation (CHIP) assays indicate that this particular effect of LAQ824 involves histone modifications at the IL-10-promoter level. Given this inhibitory effect of LAQ824 and the central role of IL-10 in immune tolerance, we asked next whether a specific histone deacetylase(s) could predominantly influence IL-10 gene expression. By utilizing a reporter gene carrying the IL10 promoter fused to a luciferase gene, plasmids coding for Flag-tagged versions of all HDACs and plasmids carrying siRNA for specific silencing of HDACs, we found that among all the HDACs evaluated, HDAC11 negatively regulates the production of IL-10 in APCs. Importantly, treatment of APCs with LAQ824 resulted in increased expression of HDAC 11, diminished IL-10 production and the generation of APCs that effectively prime naive CD4+ T-cells and restore the responsiveness of tolerized antigen-specific T-cells from lymphoma bearing hosts. Taken together, we have demonstrated for the first time that HDAC11, a member of the HDAC family with no prior defined physiological role, is involved in regulation of IL-10 gene expression. Furthermore, our findings that HDAC11 expression in APCs can be manipulated by treatment of these cells with LAQ824, points to HDAC11 as a novel therapeutic target to influence immune activation versus immune tolerance, a critical decision with significant implications in autoimmunity, transplantation and cancer immunotherapy.

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