Anergy In CD4 Research Articles

IFI35 limits antitumor immunity in triple-negative breast cancer via CCL2 secretion

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor prognosis due to the lack of therapeutic targets. Although immunotherapy brings survival benefits to patients diagnosed with TNBC, it remains limited and treatment resistance is widespread. Here we demonstrate that IFI35 is highly expressed in tumor tissues and can be induced by Interferon-γ in a time-dependent and concentration-dependent manner in breast cancer cells. In xenograft models, we reveal that IFI35 dramatically increases myeloid-derived suppressor cells infiltration in tumors, along with depletion and anergy of CD8+T cells. IFI35 ablation leads to prolonged survival of the mice. Mechanistically, RNA-sequencing reveals that IFI35 promotes CCL2 secretion, resulting in the remodeling of TNBC immune microenvironment. Ablation of IFI35 promotes the infiltration of effector CD8+T cells, and thereby sensitizes TNBC to anti-PD-1 immunotherapy. Our data suggest that IFI35 limits antitumor immunity and may be expected to become a new immunotherapy target in TNBC.

018 Imiquimod perturbs amino acid metabolism in human CD8+ T cells

Imiquimod (IMQ), a TLR7 agonist, is a standard local treatment for non-melanoma skin cancers (NMSC). IMQ triggers inflammation, ultimately resulting in immunological tumor destruction. Albeit IMQ promotes the recruitment of effector T (TE) cells, IMQ triggers anergy in CD4+ T cells. Meanwhile, how IMQ affects human CD8+ TE cells, pivotal to immunological cancer control, remains unclear. To address this, we studied CD8+ TE cell lines from NMSC and circulating, skin-homing CLA+CD8+ TE cells. In both models, IMQ-treated TE cells showed significantly reduced proliferation and IFN-γ production.

Evaluation of cytokine levels in response to mitogen among HIV-1-infected blood cells and their relationships to the number of T cells

BackgroundHuman immunodeficiency virus-1 (HIV-1) infection causes loss and anergy of CD4+ and CD8+ T cells, leading to opportunistic infections, including tuberculosis (TB). QuantiFERON®-TB (QFT) is used as a diagnostic tool to detect TB, but it exhibits limited accuracy among subjects with low CD4+ T cell numbers, including HIV-1-infected individuals. The present study aimed to determine the effect of HIV-1 infection and patients’ blood T cell numbers on cytokine production in response to mitogen (Mit) stimulation. MethodsThe number of CD4+ and CD8+ T cells in HIV-1-infected individuals was quantified. Levels of various cytokines in Mit-stimulated and un-stimulated (Nil) supernatants of QFT gold “in tube” were assessed using a MAGPIX System. The correlation between cytokine levels and CD4+/CD8+ T cell counts in response to Mit was analyzed. The cytokine levels were compared between HIV-1-infected and healthy subjects. ResultsHIV-1-infected individuals (110) and control subjects (27) were enrolled. Interferon (IFN)-γ, interleukin-1 receptor antagonist (IL-1RA), IL-6, IL-8, and regulated on activation, normal T cell expressed and secreted (RANTES) values in Mit-Nil tubes showed a significant correlation with CD4+ T cell counts, while IFN-γ, IL-6, and IFN-γ-induced protein 10 (IP-10) values in Mit-Nil tubes had significant correlation with CD8+ T cell counts. IL-1RA, IL-8, IP-10, platelet-derived growth factor (PDGF)-BB, and RANTES levels in Nil tubes were significantly higher in the HIV-1-infected group. IFN-γ, IL-2, IL-5, IL-6, IP-10, and macrophage inflammatory protein-1β values in Mit-Nil tubes were significantly higher, and PDGF-BB and RANTES levels were significantly lower in the HIV-1-infected group. ConclusionThe functions of HIV-1-infected T cells and uninfected T cells, such as spontaneous and responsive cytokine production in response to Mit, were different. Our findings may be useful for developing new clinical tools for patients with low T cell counts. Additionally, the study provides new insights into the pathogenesis of HIV-1 infection.

Runx1 is a key regulator of T cell anergy

Abstract The transcription factor Runx1 is critical for T cell development and maturation. CD4-Cre Runx1 conditional knockout mice have a block in T cell maturation, leading to complement deposition on recent thymic emigrants, and leaving very few CD4+T cells in peripheral lymphoid organs. Interestingly, thymic- and splenic-derived T cells from CD4-Cre Runx1 cKO mice exhibit increased expression of markers indicative of anergy including FR4 and CD73, which is not seen in other genetically modified mice with a block in T cell maturation. These data suggest Runx1 plays a role in regulating the development of T cell anergy in CD4+T cells. We have generated a 1:1 mixed bone marrow chimera (BMC) system with Estrogen Receptor-Cre (ER-Cre) Runx1 conditional knockout and wild type B6.SJL bone marrow to delete Runx1 in mature CD4+ T cells. Upon tamoxifen treatment and deletion of Runx1, the ER-Cre Runx1 cKO CD4+ T cells spontaneously develop an anergic phenotype as they fail to proliferate upon TCR/CD28 stimulation, and co-express CD73 and FR4. This cell surface phenotype is cell intrinsic since wild type B6.SJL CD4+ T cells in the mixed bone marrow chimera do not upregulate CD73 and FR4 upon tamoxifen treatment. Surprisingly, the mixed BMC system reveals both the ER-Cre Runx1 cKO and the wild type B6.SJL peripheral T cells fail to proliferate in response to TCR/CD28 stimulation, suggesting Runx1 also regulates a cell-extrinsic suppressive mechanism controlling T cell tolerance. This cell-extrinsic induction of anergy requires Runx1-deficient CD4+ T cells, but it is not dependent on Runx1-deficient Tregs. Thus, Runx1 is a key regulator of T cell anergy, and further analysis of this BMC model will serve to uncover the mechanism.

The Poorer-Risk AML, the Weaker Immunologic Surveillance? --Higher PD-L1 Expression on Non-APL AML Cells Is Associated with Poorer Risk Status According to Cytogenetics and Molecular Abnormailties

BackgroudThe specific recurrent cytogenetic and molecular abnormalities are significantly associated with prognosis and have been used to establish risk stratification which directs the therapeutic strategy in AML. Whether the immune surveillance contributes to the prognosis according to the cytogenetic and molecular risk status is unknown. The checkpoint PD-1/PD-L1 pathway is involved in the tumor surveillance. Down-regulation of PD-1/PD-L1 pathway caused a slower AML progression in mouse models through anergy of CD8+ CTL cells. Clinical trials of PD-1/PD-L1 inhibitor-based regimens in patients with AML are ongoing and seem to have promising results. But few studies investigated clinical significance of PD-L1 expression on leukemic cells in AML patients.MethodWe prospectively observed 120 consecutive adult patients with non-APL AML. PD-L1 mRNA of bone marrow mononuclear cells at diagnosis was detected by RT-PCR and the specific fluorescence indices (SFI) of PD-L1 expression on bone marrow blast cells was determined by flow cytometry. Cytogenetic and molecular genetic risks were assessed according to NCCN AML guideline (2016 version 2). Patients with age >60 years or failure of karyotype analysis were excluded. All remaining 95 patients were treated with "3+7" idarubicine and cytarabine induction regimen. Patients with response of ≥PR were administered the same regimen as the initial chemotherapy, and then consolidated with intermediate-dose cytarabine for four cycles followed by MA, AA, HA and AE regimens subsequently. Patients at poor risk or with unsatisfied controlled minimal residual disease were recommended allogeneic transplantation (allo-HCT). Among the patients with indication of allo-HCT, those who had both donor and desire received allo-HCT after 3 cycles of consolidation in their first CR (CR1).ResultThe diagnoses according to morphology included AML-M0 (n=1), AML-M1 (n=5), AML-M2 (n=55), AML-M4 (n=19), AML-M5 (n=13) and AML-M6 (n=2). Twenty patients were at favorable risk, 43 were at intermediate risk and 32 were at poor risk. We found a correlation between SFIs of PD-L1 and PD-L1 mRNA (r=0.413, P<0.001). After the base 10 logarithm transformation, quantity of PD-L1 mRNA in mononuclear cells of bone marrow were different among all risk groups (P=0.025). Post Hoc multiple comparisons showed PD-L1 mRNA of poor-risk group was higher than that of favorable-risk group (P=0.008). PD-L1 mRNA of the intermediate-risk group was also higher when compared to that of favorable-risk group (P=0.029). SFIs of PD-L1 on leukemic cells was higher in poor-risk group than in either intermediate-risk (P=0.040) or favorable-risk group (P=0.042), although no statistic difference was found among three groups (P=0.057). With ROC curves, we found PD-L1 mRNA could well predict both the early CR defined as the CR achieved after the initial chemotherapy (AUC=0.736, P=0.050) and the final CR defined as CR1 achieved after any cycles of induction chemotherapy (AUC=0.911, P=0.006). SFI of PD-L1 on leukemic cells could only predict the final CR (AUC=0.889, P=0.009). With both the best specificity of 0.833 and sensitivity of 1.000 for predicting final CR and specificity of 0.667 and sensitivity of 0.917 for predicting early CR, the cutoff value of PD-L1 mRNA was identified as 0.0681. SFI of PD-L1 less than 1.852 was a good predictor for achieving final CR with the sensitivity of 0.800 and specificity of 1.000. PD-L1 mRNA≥0.0681 was the only independent poor-risk factor for the early CR (HR=12.697, 95%CI 2.710-59.481, P<0.001).ConclusionAML cells with poorer-risk cytogenetic and molecular abnormalities seemed to have a higher PD-L1 expression which may compromise the leukemic immune surveillance by CTL suppression. Higher PD-L1 expression on AML cells was associated with poorer response to IA-based induction regimens. DisclosuresNo relevant conflicts of interest to declare.

Lymph node stromal cells constrain immunity via MHC class II self-antigen presentation.

Non-hematopoietic lymph node stromal cells shape immunity by inducing MHC-I-dependent deletion of self-reactive CD8+ T cells and MHC-II-dependent anergy of CD4+ T cells. In this study, we show that MHC-II expression on lymph node stromal cells is additionally required for homeostatic maintenance of regulatory T cells (Tregs) and maintenance of immune quiescence. In the absence of MHC-II expression in lymph node transplants, i.e. on lymph node stromal cells, CD4+ as well as CD8+ T cells became activated, ultimately resulting in transplant rejection. MHC-II self-antigen presentation by lymph node stromal cells allowed the non-proliferative maintenance of antigen-specific Tregs and constrained antigen-specific immunity. Altogether, our results reveal a novel mechanism by which lymph node stromal cells regulate peripheral immunity.

MicroRNA-mediated regulation of mTOR complex components facilitates discrimination between activation and anergy in CD4 T cells

microRNA-mediated regulation of mTOR complex components facilitates discrimination between activation and anergy in CD4 T cells

MicroRNA-mediated regulation of mTOR complex components facilitates discrimination between activation and anergy in CD4 T cells.

T cell receptor (TCR) signals can elicit full activation with acquisition of effector functions or a state of anergy. Here, we ask whether microRNAs affect the interpretation of TCR signaling. We find that Dicer-deficient CD4 T cells fail to correctly discriminate between activating and anergy-inducing stimuli and produce IL-2 in the absence of co-stimulation. Excess IL-2 production by Dicer-deficient CD4 T cells was sufficient to override anergy induction in WT T cells and to restore inducible Foxp3 expression in Il2-deficient CD4 T cells. Phosphorylation of Akt on S473 and of S6 ribosomal protein was increased and sustained in Dicer-deficient CD4 T cells, indicating elevated mTOR activity. The mTOR components Mtor and Rictor were posttranscriptionally deregulated, and the microRNAs Let-7 and miR-16 targeted the Mtor and Rictor mRNAs. Remarkably, returning Mtor and Rictor to normal levels by deleting one allele of Mtor and one allele of Rictor was sufficient to reduce Akt S473 phosphorylation and to reduce co-stimulation-independent IL-2 production in Dicer-deficient CD4 T cells. These results show that microRNAs regulate the expression of mTOR components in T cells, and that this regulation is critical for the modulation of mTOR activity. Hence, microRNAs contribute to the discrimination between T cell activation and anergy.

Rapamycin induces ILT3highILT4high dendritic cells promoting a new immunoregulatory pathway

ILT3(high)ILT4(high) dendritic cells (DCs) may cause anergy in CD4(+)CD45RO(+)CD25(+) T cells transforming them into regulatory T cells (Tregs). Here, we tested whether chronic exposure to rapamycin may modulate this immunoregulatory pathway in renal transplant recipients. Forty renal transplant patients with biopsy-proven chronic allograft nephropathy and receiving calcineurin inhibitors were randomly assigned to either calcineurin inhibitor dose reduction or withdrawal with rapamycin introduction. At conversion and 2 years thereafter, we measured the rapamycin effects on circulating DCs (BDCA1/BDCA2 and ILT3/ILT4 expression), CD4(+)/CD25(high)/Foxp3(+) Tregs, CD8(+)/CD28(-) T cells, and the Th1/Th2 balance in graft biopsies. In rapamycin-treated patients, peripheral BDCA2(+) cells were significantly increased along with ILT3/ILT4(+) DCs. The number of circulating CD4(+)/CD25(high)/Foxp3(+)/CTLA4(+) Tregs, CD8(+)CD28(-) T cells, and HLA-G serum levels were higher in the rapamycin-treated group. The number of ILT3/ILT4(+)BDCA2(+) DC was directly and significantly correlated with circulating Tregs and CD8(+)CD28(-) T cells. ILT3/ILT4 expression was increased in kidney biopsies at the end of the study period along with a significant bias toward a Th2 response within the graft only in the rapamycin-treated patients. Thus, rapamycin induces the upregulation of ILT3 and ILT4 on the DC surface, and this effect is associated with an increase in the number of Tregs and expansion of the CD8(+)CD28(-) T cell population. This suggests that mTOR inhibition may promote a novel immunoregulatory pathway.

Alveolar Macrophages Contribute to Respiratory Tolerance by Inducing FoxP3 Expression in Naive T Cells

Alveolar macrophages (AMs) from mice and humans have long been known to contribute to maintaining tolerance in the lung. Studies have shown that AMs can induce anergy in CD4(+) T cells. Nitric oxide, prostaglandins, and leukotrienes have been implicated in AM-mediated tolerance. However, it remains unclear what effect, if any, AMs exert on FoxP3 induction in CD4(+) T cells from mice and humans, and whether or not other immunomodulators might play a role. AMs were isolated from bronchoalveolar lavage (BAL) fluid from either mice or humans, and cocultured with enriched naive CD4(+)FoxP3(-) T cells. We show here for the first time that AMs and AM-conditioned media (AM-CM) from mice and humans induced FoxP3 expression in naive CD4(+) T cells in vitro, an outcome that was reversed in part either by inhibiting retinoic acid (RA) binding to its receptor (RAR), or by blocking transforming growth factor (TGF)-β₁ signaling. A nasal administration of the RAR antagonist reduced the frequencies of CD4(+)FoxP3(+) T cells in the lungs of mice after aerosol challenge with Bordetella pertussis. In addition, we found that the intranasal vaccination of mice with ovalbumin (OVA) protein in conjunction with an RAR inhibitor led to a significant increase in OVA-specific serum IgE. Our findings suggest that AMs can mediate tolerance in the lungs of mice and humans via RA and TGF-β₁. These data may have implications in the development of nasal vaccines in the future.

Anti-Inflammatory Therapy for Feline Immunodeficiency Virus Infection and Associated AIDS-Like Syndrome

Feline immunodeficiency virus (FIV) is a lentivirus that can infect several feline species, among them the domestic cat. Related lentiviruses are prevalent in non-domestic felids (Olmsted et al., 1992). The isolation of FIV from cats who while having an immunodeficiency-like illness were seronegative for Feline leukemia virus (FeLV), was first described in 1987 (Pedersen et al., 1987). FIV is classified into five phylogenetic subtypes, A through E, according to the nucleotide sequence diversity in the env gene that encodes for the viral envelop proteins. Subtypes A and B are most prevalent worldwide (Samman et al., 2011). The seroprevalence differs between regions, with 1–14% in clinically asymptomatic domestic cats and up to 44% in sick cats (Hosie et al., 2009). Feline immunodeficiency virus transmission occurs naturally mainly through biting, but vertical transmission between mother and kittens is also possible (Yamamoto et al., 1989). Transmission occurs more easily when an uninfected cat is exposed to infected cells, although lower levels of the virus are also present in colostrum, saliva, plasma, and seminal fluid (Yamamoto et al., 2007). After acute infection FIV can cause a AIDS-like syndrome in domestic cats, with many similarities to HIV-induced AIDS in man (Elder et al., 2010). Progression of the chronic lentivirus infection is associated with a decline in CD4+ T lymphocytes and CD4+:CD8+ ratio during a asymptomatic phase. During this period plasma virus load remains stable (Hosie et al., 2009). When the CD4+ T lymphocyte count falls below a certain number immune dysfunction will become apparent, accompanied by secondary and opportunistic infections (Willett et al., 1997). In addition to the ability to infect CD4+ T lymphocytes, FIV also infects several other immune cells, including monocytes/macrophages, B cells, CD4+CD25+ T cells, and CD8+ T cells (Yamamoto et al., 2007). Currently practiced therapy focuses on immune stimulation, vaccination, and treatment of secondary diseases. Immune stimulation has been suggested in the form of GM-CSF, IFN-alpha, and IFN-tau among others (Arai et al., 2000; Pedretti et al., 2006; Chon and Bixler, 2010). These therapies are based on the notion that the CD4+ T lymphocyte depletion in feline AIDS is the direct consequence of viral killing by FIV (the “viral killing hypothesis”). In this theory high turnover of T lymphocytes and eventually exhaustion is a response to viral destruction of CD4+ T lymphocytes. It has also been suggested however, that activation-induced CD4+ T lymphocyte death may be a major factor in progression to AIDS in humans (Groux et al., 1992; Hazenberg et al., 2003), which corresponds with the absence of CD4+ T lymphocyte decline in naturally Simian immunodeficiency virus (SIV) infected Sooty Mangabeys (Silvestri et al., 2003). These primates show a high viral load, but limited SIV CD4+ T lymphocyte cytopathicity. Therefore chronic (hyper-)activation of the immune system may also play a significant role in FIV pathogenesis (Figure ​(Figure1).1). This hyper-activation is seen in both CD4+ and CD8+ T lymphocyte populations, with a rise in B7+CTLA4+ phenotype, and increase in B lymphocyte polyclonal responses (Tompkins and Tompkins, 2008). The B7+CTLA4+ T lymphocytes cause an induction of anergy and apoptosis through T–T lymphocyte interactions, which leads to CD4+ T lymphocyte depletion. Figure 1 Chronic antigenemia induces immune hyper-activation that leads to immune suppression. This process may be inhibited by anti-inflammatory or immunosuppressive drugs that reduce T-cell activation. Partly the depletion of CD4+ T lymphocytes may also be due to the activation of CD4+CD25+ T regulatory (Treg) cells in FIV-infected cats. Previous studies suggested that a proper immune response is lost during the acute phase FIV infection (Mexas et al., 2008). It's possible that CD4+CD25+ T regulatory lymphocytes induce anergy in CD4+ and CD8+ T cells (Vahlenkamp et al., 2004). This knowing, it could be meaningful investigating which mechanisms cause the activation of CD4+CD25+ Treg cells and if it can be suppressed effectively during the acute phase of FIV infections, without losing an effective immune response. CD4+ and CD8+ T-cells functioning may improve when CD4+CD25+ Treg cells are suppressed and slow progression to AIDS. In light of this evidence it is important to explore the effectiveness of immunosuppressive or anti-inflammatory treatment in the prevention of progression to AIDS in FIV-infected cats. Suggested pharmaceuticals for this type of treatment for HIV are cyclosporin A and corticosteroids (Groux et al., 1992; Lawn et al., 2001). It should however be noted that although this type of treatment may diminish the detrimental effect of immune hyper-activation, antiretroviral drugs, that for example inhibit FIV enzymes (Savarino et al., 2007), should be used or developed to alleviate the potential effects of immunosuppression on viral replication.

Histone deacetylase inhibitor uses p21 Cip1 to maintain anergy in CD4 + T cells

T cell anergy defined as antigen-specific proliferative unresponsiveness was induced in CD4 + T cells exposed to antigen (Ag) in the presence of the histone deacetylase (HDAC) inhibitors n-butyrate, trichostatin A or scriptaid. However, the ability of HDAC inhibitors to induce anergy in Th1 cells was not due to general histone hyperacetylation. Instead, the anergy induced by HDAC inhibitors was associated with upregulation of p21 Cip1, a secondary effect of histone acetylation. Induction of p21 Cip1 in the absence of histone hyperacetylation by exposure to okadaic acid also resulted in T cell anergy. In addition, Ag-specific p21 Cip1-deficient CD4 + T cells were much less susceptible to anergy induction by n-butyrate. Thus, p21 Cip1 appears to mediate the proliferative unresponsiveness found in CD4 + T cell anergized by exposure to Ag in the presence of HDAC inhibitors.

Blockade of CD26-mediated T cell costimulation with soluble caveolin-1-Ig fusion protein induces anergy in CD4 +T cells

CD26 binds to caveolin-1 in antigen-presenting cells (APC), and that ligation of CD26 by caveolin-1 induces T cell proliferation in a TCR/CD3-dependent manner. We report herein the effects of CD26–caveolin-1 costimulatory blockade by fusion protein caveolin-1-Ig (Cav-Ig). Soluble Cav-Ig inhibits T cell proliferation and cytokine production in response to recall antigen, or allogeneic APC. Our data hence suggest that blocking of CD26-associated signaling by soluble Cav-Ig may be an effective approach as immunosuppressive therapy.

Depletion of the programmed death-1 receptor completely reverses established clonal anergy in CD4 + T lymphocytes via an interleukin-2-dependent mechanism

Recent studies have implicated the cell surface receptor Programmed Death-1 (PD-1) in numerous models of T cell anergy, though the specific mechanisms by which the PD-1 signal maintains tolerance is not clear. We demonstrate that the depletion of PD-1 with siRNA results in a complete reversal of clonal anergy in the A.E7 T cell model, suggesting that the mechanism by which PD-1 maintains the anergic phenotype is a T-cell-intrinsic phenomenon, and not one dependent on other cell populations in vivo. We have also shown that the neutralization of IL-2 during restimulation abrogates the effect of PD-1 depletion, suggesting that tolerance mediated by PD-1 is wholly IL-2 dependent, and likewise intrinsic to the tolerized cells.

T1212 Upregulation of E3 Ubiquitin Ligases Related to T Cell Anergy in CD4+ T Cells Isolated from Patients with Ulcerative Colitis in Remission

Background and Aims Insufficient tolerance against luminal antigens is suggested to cause inflammatory bowel diseases including ulcerative colitis (UC). T cell anergy is one of the mechanisms regulating immune tolerance. Recently, some E3 ubiquitin ligases are reported to downregulate downstream signals of T cell receptor and induce T cell anergy. The aim of this study was to investigate the state of T cell anergy in healthy subjects and UC patients by quantitating the expression of E3 ubiquitin ligases, GRAIL, c-Cbl, Itch, all of which are reported to induce anergy on T cells. Patients and Methods Peripheral mononuclear cells were obtained from 20 UC patients (active UC: 12, UC in remission: 8) and 10 healthy volunteers (HV) by either centrifugal leukocytapheresis or sampling of peripheral blood. CD4+ T cells were isolated by magnetic cell sorter and expressions of GRAIL, c-Cbl, and Itch mRNA in these cells were measured by real-time quantitative RT-PCR. The level of GRAIL, c-Cbl, and Itch mRNA expression were compared between in active UC patients, UC patients in remission, and HV. The expression of these ubiquitin ligases were followed in 6 active UC patients who were treated by corticosteroid and centrifugal leukocytapheresis. Results Anergic CD4+ T cells obtained by ionomycin treatment In Vitro revealed higher GRAIL, c-Cbl, and Itch expression when compared with non-anergic T cells. GRAIL was predominantly expressed on CD4+ T cells whereas c-Cbl and Itch were also expressed on non-CD4+ T cell subsets. The GRAIL expression in CD4+ T cells of UC patients in remission was significantly higher than that of active UC patients or that of HV (p<0.01). The c-Cbl and Itch expressions in CD4+ T cells of UC patients in remission were relatively higher than that of active UC or that of HV, but there were no significant differences. Remarkably the levels of GRAIL expression were significantly increased after the treatment in UC patients whose clinical activities ewre improved by the treatment. However, the c-Cbl and Itch expression did not increase after the treatment. Conclusion Among the 3 different E3 ubiquitin ligases which induce T cell anergy, upregulation of GRAIL expression seems to be associated with the induction of remission in UC patients. These results indicate that GRAIL is a potential therapeutic target of inflammatory bowel disease.

CD137 ligand prevents the development of T‐helper type 2 cell‐mediated allergic asthma by interferon‐γ‐producing CD8+ T cells

Allergic asthma is a T-helper type 2 (Th2) cell-mediated chronic disease that is characterized by airway hyperreactivity (AHR) and chronic eosinophilic airway inflammation. Several studies suggest co-stimulatory molecules like CD137 as potential targets for therapeutic interventions in allergic airway disease. Recently, we could show in a murine asthma model that administration of an agonistic antibody against the receptor of the co-stimulatory molecule CD137 prevented and even reversed an already-established asthma phenotype. The purpose of this study was to analyse the effect of stimulation of the CD137 ligand by a monoclonal antibody (CD137L mAb). To induce an asthma-like phenotype, BALB/c mice were sensitized to ovalbumin (OVA), followed by an intrapulmonary allergen challenge. Anti-CD137L or control mAb were applied 1 day before OVA immunization or after the asthma phenotype was already established. Stimulation of the CD137L instead of the receptor by CD137L mAb prevents the development of an asthma-like phenotype but does not reverse established disease. While the receptor-mediated effect is partly mediated by anergy of CD4(+) T cells and partly by induction of IFN-gamma-producing CD8(+) T cells, the effect of the CD137L mAb is completely dependent on IFN-gamma-producing CD8(+) T cells: blockade of IFN-gamma and depletion of CD8(+) T cells fully abrogated the observed protective effect. In vitro experiments showed that the anti-CD137L mAb ligates directly to CD8(+) T cells and induces the generation of IFN-gamma by this cell population. Our results demonstrate that anti-CD137L mAb prevents disease development via IFN-gamma-producing CD8(+) T cells but is inferior to stimulation of the receptor that reverses established disease by a mechanism including CD4(+) T cell anergy.

Response of T cells &amp;lt;italic&amp;gt;in vivo&amp;lt;/italic&amp;gt; Induced by Repeated Superantigen Treatments at Different Time Intervals

We have investigated the response of T cells to staphylococcal enterotoxin A (SEA) injections in vivo. We found that a single injection of SEA with an optimal dose of 10 microg increased the expression of both CD4 and CD8 significantly. There was expansion of SEA-reactive T cells in vivo after SEA re-injection and the time interval between injections strongly influenced the responsiveness of CD4+ and CD8+ T cells. Anergy of T cells was observed after three SEA treatments. The time interval between injections mainly affected the unresponsiveness of CD4+ T cells, not CD8+ T cells. Marked deletion followed by anergy of CD4+ T cells was induced at short intervals, and anergy without obvious deletion of CD4+ T cells was induced at long intervals. We also found that the anergic state was reversible in vivo. Repeated SEA stimulation led to down-regulation of interleukin (IL)-2, and high levels of IL-10. This study showed that both CD4+ and CD8+ SEA-primed T cells were responsive to SEA rechallenge in vivo, and a third injection was needed to induce the anergy of T cells.

Anergy is a Survival Advantage for the Maintenance of Memory CD4+ T Cells (36.10)

Abstract The hallmarks of specific T cell immunity include proliferative expansion, and acquisition of effector function. The outcome is resolution of the infection and the generation of memory T cells (Tmem). Although majority of Tmem cells die following clearance of infection, a fraction survives through lifetime and is protective on recall. It is not clear how Tmem decline with the fall of antigenic load and survive so long in the absence of antigen. Using CpG mixed with antigen to mimic an infection, we have shown that CD4+ Tmem cells undergo anergy upon encountering suboptimal doses of antigen, a condition that associates with the fall of antigenic load expected post resolution of an infection. We demonstrate that follicular B (B2) cells, and not DCs, induce anergy in CD4+ Tmem by upregulating CTLA-4 expression. These findings suggest that B cells bearing high affinity antigen receptor regulate responsiveness of Tmem by capturing the lowest levels of antigen likely present after the clearance of an infection, and signal Tmem to undergo anergy. We also show that the anergized cells are activated by stimulatory signals generated by innate immunity at the onset of a subsequent infection. Our study suggest that anergy is a mechanism to regulate long-term survival of Tmem in the absence of antigen by preventing unnecessary proliferations that lead to death. Supported by R01GM53549 and R01AI063764 grants to SS-N.

Recombinant Ig-Like Transcript 3-Fc Modulates T Cell Responses via Induction of Th Anergy and Differentiation of CD8+ T Suppressor Cells

The Ig-like transcript (ILT)3 is crucial to the tolerogenic activity acquired by dendritic cells exposed to allospecific T suppressor (Ts) cells. We have explored the immunomodulatory property of the extracellular region of ILT3 using a cytoplasmic deletion mutant of ILT3 (ILT3delta), expressed as membrane-bound ILT3 on KG1 cells, and a rILT3-Fc fusion protein. We found that both membrane-bound and soluble ILT3 inhibited T cell proliferation in primary and secondary MLC inducing anergy in CD4+ Th cells and suppressing the differentiation of IFN-gamma-producing CD8+ CTL. Furthermore, membrane-bound and soluble ILT3 induced the differentiation of CD8+ FOXP3+ Ts cells in primary 7-day MLC. The suppressive activity of these CD8+ Ts cells is alloantigen specific and mediated by their capacity to induce the up-regulation of ILT3 and down-regulation of costimulatory molecules such as CD86 in APC from the stimulator used for priming, but not on control HLA-mismatched APC. Our finding that ILT3-Fc has potent immunosuppressive activity in vitro and that it acts on T cells only upon activation suggests the possibility that this agent may be of use for specific suppression of the immune response in autoimmunity or transplantation.

Central memory CD4 T cells are the predominant cell subset resistant to anergy in SIV disease resistant sooty mangabeys

HIV infection in humans and experimental SIV infection in rhesus macaques leads to the loss of recall antigen responses, immunological anergy in CD4 T cells and AIDS. In contrast, natural infection in sooty mangabeys with SIV does not lead to disease despite high viral loads accompanied by resistance of their CD4 T cells to undergo immunological anergy. The objective of the study was to further elucidate the mechanisms that contribute to anergy resistance in CD4 T cells from sooty mangabeys and identify whether the anergy resistance is a function of a specific subset or the entire cell population. Susceptibility or resistance to anergy was analyzed in antigen specific and defined CD4 T cell subsets from peripheral blood of sooty mangabeys and rhesus macaques by using an in vitro anergy inducing protocol; expression of the anergy associated gene GRAIL was measured. Antigen specific CD4 T cells from SIV disease resistant sooty mangabey are relatively resistant to the development of anergy. This resistance is associated with a lack of an upregulation of GRAIL. Conversely, rhesus macaque CD4 T cells are sensitive to anergy induction associated with upregulation of GRAIL. Furthermore the anergy resistant phenotype of sooty mangabey CD4 T cells predominantly resides in central memory cells defined either as CD4+CD45RA-CD62L+ or CD4+CD28+CD95+CCR7+. The maintenance of recall responses in sooty mangabeys is associated with the resistance of central memory CD4 T cells to the induction of anergy which may represent an important mechanism underlying SIV disease resistance in this species.