Defective CD8 Research Articles

Signal inhibition by the dual-specific phosphatase 4 impairs T cell-dependent B-cell responses with age

T cell-dependent B-cell responses decline with age, suggesting defective CD4 T-cell function. CD4 memory T cells from individuals older than 65 y displayed increased and sustained transcription of the dual-specific phosphatase 4 (DUSP4) that shortened expression of CD40-ligand (CD40L) and inducible T-cell costimulator (ICOS) (both P < 0.001) and decreased production of IL-4, IL-17A, and IL-21 (all P < 0.001) after in vitro activation. In vivo after influenza vaccination, activated CD4 T cells from elderly individuals had increased DUSP4 transcription (P = 0.002), which inversely correlated with the expression of CD40L (r = 0.65, P = 0.002), ICOS (r = 0.57, P = 0.008), and IL-4 (r = 0.66, P = 0.001). In CD4 KO mice reconstituted with DUSP4 OT-II T cells, DUSP4 had a negative effect on the expansion of antigen-specific B cells (P = 0.003) and the production of ova-specific antibodies (P = 0.03) after immunization. Silencing of DUSP4 in memory CD4 T cells improved CD40L (P < 0.001), IL-4 (P = 0.007), and IL-21 (P = 0.04) expression significantly more in the elderly than young adults. Consequently, the ability of CD4 memory T cells to support B-cell differentiation that was impaired in the elderly (P = 0.004) was restored. Our data suggest that increased DUSP4 expression in activated T cells in the elderly in part accounts for defective adaptive immune responses.

Defective CD8 T Cell Responses in Aged Mice Are Due to Quantitative and Qualitative Changes in Virus-Specific Precursors

Aging is associated with suboptimal CD8 T cell responses to viral infections. It is not clear whether these poor responses are due to environmental influences or quantitative and qualitative changes in the pool of responding CD8 T cells. Our studies demonstrated several deleterious age-related changes in the pool of Ag-specific CD8 T cells that respond to infection. The majority of CD8 T cells from uninfected aged mice was CD44(Hi) and had increased expression of inhibitory receptors including PD1, LAG3, 2B4, and CD160. These aged CD44(Hi) CD8 T cells were transcriptionally similar to exhausted CD8 T cells found during chronic infections. In addition, the number of virus-specific precursors in aged mice prior to infection was decreased up to 10-fold, and many of these Ag-specific precursors had high expression of CD44 and PD1. Finally, TCR transgenic studies demonstrated that the CD44(Hi) Ag-specific CD8 T cells from unimmunized aged and young mice were qualitatively inferior compared with CD44(Lo) CD8 T cells from aged or young donors. Thus, a decrease in precursor frequency as well as qualitative changes of CD8 T cells during aging are directly related to impaired immunity.

Anergic CD8+ T Lymphocytes Have Impaired NF-κB Activation with Defects in p65 Phosphorylation and Acetylation

Because of the cytotoxic potential of CD8(+) T cells, maintenance of CD8(+) peripheral tolerance is extremely important. A major peripheral tolerance mechanism is the induction of anergy, a refractory state in which proliferation and IL-2 production are inhibited. We used a TCR transgenic mouse model to investigate the signaling defects in CD8(+) T cells rendered anergic in vivo. In addition to a previously reported alteration in calcium/NFAT signaling, we also found a defect in NF-κB-mediated gene transcription. This was not due to blockade of early NF-κB activation events, including IκB degradation and NF-κB nuclear translocation, as these occurred normally in tolerant T cells. However, we discovered that anergic cells failed to phosphorylate the NF-κB p65 subunit at Ser(311) and also failed to acetylate p65 at Lys(310). Both of these modifications have been implicated as critical for NF-κB transactivation capacity, and thus, our results suggest that defects in key phosphorylation and acetylation events are important for the inhibition of NF-κB activity (and subsequent T cell function) in anergic CD8(+) T cells.

Immune-Related Disorders and Extrahepatic Diseases in Chronic HCV Infection

Immune-Related Disorders and Extrahepatic Diseases in Chronic HCV Infection

Hydroxychloroquine drastically reduces immune activation in HIV-infected, antiretroviral therapy–treated immunologic nonresponders

AbstractDespite optimal suppression of HIV replication, restoration of CD4+ T cells is not always achieved in antiretroviral therapy–treated individuals. Defective CD4 recovery in immunologic nonresponders is possibly associated with TLR-mediated immune activation driven by alterations of gut permeability. Hydroxychloroquine (HCQ) reduces endosomal TLR signaling; thus, we verified whether HCQ could dampen immune activation and be associated with an increase in CD4+ T cells. To this end, we enrolled in a prospective study 20 HIV-infected immunologic nonresponders (CD4 count < 200 cells/mL or CD4 increase < 5% in the last 12 months) who received 400 mg/day HCQ for 6 months. HCQ had a notable impact on immune activation as shown by significant modifications of the following parameters: (1) reduced plasma lipopolysaccharide; (2) decreased TLR4-expressing CD14+ cells, TLR4-mediated signal transduction, and mRNA synthesis; (3) reduced percentages of activated CD4+ (CD4+/Ki67+) and CD14+ (CD14+/CD69+) cells; (4) increased T-regulatory cells (Tregs), naive Tregs, and TLR4-expressing Tregs; (5) augmented plasmacytoid dendritic cells and reduced IFNα-secreting plasmacytoid dendritic cells; and (6) reduced IL-6 and TNFα production. HCQ-induced immune modulation was associated with increased percentages of circulating CD4+ T cells and was mostly retained 2 months after therapy interruption. HCQ reduces lipopolysaccharide/TLR-mediated immune activation; this compound could be a useful immunomodulant in HIV-infected patients. This study is registered at EutraCT as 2009-012499-28 with study number HLS01/2009-1-16-03-2009.

P29 Reduced expression of Tim-3 renders Th1 and Th17 effector cells less amenable to T-reg control in autoimmune hepatitis

IntroductionIn autoimmune hepatitis (AIH), CD4 effector immune responses are permitted by defective CD4+CD25+ regulatory T-cells (T-regs). In murine studies apoptosis of Th1 effector cells is mediated by binding of T-cell-immunoglobulin-and-mucin-domain3...

Environmental Factors Develop Different Patterns of Immune Disease

I read with interest the article by Schmidt (2011) on the sprawling explosion of autoimmune diseases and its link to environmental exposure. Schmidt (2011) summarized the problematic state of the field: Systemic autoimmune diseases are common but thought rare; their clinical identification is far from the medical school description; and they continue to be identified as an autoantibody–target–manifestation scheme. Experience shows that a patient develops different autoantibodies through the lifespan, with different clinical patterns within each phase; deeper investigation shows that organ autoimmune disease is in fact systemic. Likewise, allergy, food intolerance, cancer, and immunodeficiency (all broad diseases that are immune in nature) cross and share autoimmunity. This suggests that immature immune systems are promoted and prevented from natural selection in the era of antibiotics, but they pay the cost of fostered health dysfunctions or diseases exposed to the current complex hostile environment. I noticed this complex scenario in a survey of 22 patients reporting sick building syndrome (Blasco 2011). Although reported data was limited to autoimmune cases and the involved substances were not yet identified, I found that the same environment triggered and worsened other immune disorders. The health of two patients with asthma inexplicably worsened when they started to work in the building. One patient developed gynecological cancer; another patient, who had a past history of Hodgkin’s lymphoma, developed chronic fever and fatigue again that lasted 3 years, until she was relocated. Some of the patients reported new adult onset of clinical intolerance of milk or other foods, and one patient was positive in a breath test for lactose intolerance. A review of family histories revealed that in 20% of the patients, more than one direct relative was affected by cancer. Personnel records showed that allergy was present in 59% of the patients; recurrent infections during childhood were common; 20% required amigdalectomy. One patient suffered rheumatic fever; one patient had not been effectively immunized after repeated hepatitis vaccines; and another had defective CD4 and suffered recurrent pneumococcal infections. It would be surprising if these illnesses did not share a common root in the immune system. Schmidt (2011) underlined rising prevalence rates of autoimmunity and discussed causes. I believe that this trend is relevant in general to immune disorders because of different reactions within the same scope of lymphocyte dysfunction in response to our new aggressive environment.

Gamma Interferon Controls Mouse Polyomavirus InfectionIn Vivo

Human polyomaviruses are associated with substantial morbidity in immunocompromised patients, including those with HIV/AIDS, recipients of bone marrow and kidney transplants, and individuals receiving immunomodulatory agents for autoimmune and inflammatory diseases. No effective antipolyomavirus agents are currently available, and no host determinants have been identified to predict susceptibility to polyomavirus-associated diseases. Using the mouse polyomavirus (MPyV) infection model, we recently demonstrated that perforin-granzyme exocytosis, tumor necrosis factor alpha (TNF-α), and Fas did not contribute to control of infection or virus-induced tumors. Gamma interferon (IFN-γ) was recently shown to inhibit replication by human BK polyomavirus in primary cultures of renal tubular epithelial cells. In this study, we provide evidence that IFN-γ is an important component of the host defense against MPyV infection and tumorigenesis. In immortalized and primary cells, IFN-γ reduces expression of MPyV proteins and impairs viral replication. Mice deficient for the IFN-γ receptor (IFN-γR(-/-)) maintain higher viral loads during MPyV infection and are susceptible to MPyV-induced tumors; this increased viral load is not associated with a defective MPyV-specific CD8(+) T cell response. Using an acute MPyV infection kidney transplant model, we further show that IFN-γR(-/-) donor kidneys harbor higher MPyV levels than donor kidneys from wild-type mice. Finally, administration of IFN-γ to persistently infected mice significantly reduces MPyV levels in multiple organs, including the kidney, a major reservoir for persistent mouse and human polyomavirus infections. These findings demonstrate that IFN-γ is an antiviral effector molecule for MPyV infection.

Reduced‐intensity conditioning haematopoietic cell transplantation for haemophagocytic lymphohistiocytosis: an important step forward

Haemophagocytic lymphohistiocytosis (HLH) is a life-threatening immunodeficiency characterized by severe systemic hyper-inflammatory responses to infectious or other triggers of the immune system. In many patients, the underlying cause of HLH is a genetic defect leading to defective CD8(+) T cell and natural killer cell granule-mediated cytotoxicity. The treatment of HLH consists principally of immune suppression followed by allogeneic haematopoietic cell transplantation (HCT) to cure the underlying defect and prevent relapse of HLH. Initial treatment regimens consist of steroids coupled with either etoposide or antithymocyte globulin, ± ciclosporin. Complete responses are observed in only 50-75% of patients and even after a complete response, relapse and death still occur. The only definitive, long-term cure for patients with genetic forms of HLH is allogeneic HCT. Unfortunately, allogeneic HCT for patients with HLH is often complicated by critical illness, extensive organ involvement, active infections, or refractory HLH. For these reasons, patients are unusually prone to developing transplant-related toxicities and complications. In recent years, great strides have been made with regard to the care and transplantation of patients with HLH. Here we review the current state of the treatment of patients with HLH with allogeneic HCT, highlighting the important steps forward that have been made with reduced-intensity conditioning.

CD8(+) Tregs in autoimmunity: learning "self"-control from experience.

Autoreactive CD8(+) regulatory T cells (Tregs) play important roles as modulators of immune responses against self, and numerical and functional defects in CD8(+) Tregs have been linked to autoimmunity. Several subsets of CD8(+) Tregs have been described. However, the origin of these T cells and how they participate in the natural progression of autoimmunity remain poorly defined. We discuss several lines of evidence suggesting that the autoimmune process itself promotes the development of autoregulatory CD8(+) T cells. We posit that chronic autoantigenic exposure fosters the differentiation of non-pathogenic autoreactive CD8(+) T cells into antigen-experienced, memory-like autoregulatory T cells, to generate a "negative feedback" regulatory loop capable of countering pathogenic autoreactive effectors. This hypothesis predicts that approaches capable of boosting autoregulatory T cell memory will be able to blunt autoimmunity without compromising systemic immunity.

Potential Role of Invariant NKT Cells in the Control of Pulmonary Inflammation and CD8+ T Cell Response during Acute Influenza A Virus H3N2 Pneumonia

Influenza A virus (IAV) infection results in a highly contagious respiratory illness leading to substantial morbidity and occasionally death. In this report, we assessed the in vivo physiological contribution of invariant NKT (iNKT) lymphocytes, a subset of lipid-reactive αβ T lymphocytes, on the host response and viral pathogenesis using a virulent, mouse-adapted, IAV H3N2 strain. Upon infection with a lethal dose of IAV, iNKT cells become activated in the lungs and bronchoalveolar space to become rapidly anergic to further restimulation. Relative to wild-type animals, C57BL/6 mice deficient in iNKT cells (Jα18(-/-) mice) developed a more severe bronchopneumonia and had an accelerated fatal outcome, a phenomenon reversed by the adoptive transfer of NKT cells prior to infection. The enhanced pathology in Jα18(-/-) animals was not associated with either reduced or delayed viral clearance in the lungs or with a defective local NK cell response. In marked contrast, Jα18(-/-) mice displayed a dramatically reduced IAV-specific CD8(+) T cell response in the lungs and in lung-draining mediastinal lymph nodes. We further show that this defective CD8(+) T cell response correlates with an altered accumulation and maturation of pulmonary CD103(+), but not CD11b(high), dendritic cells in the mediastinal lymph nodes. Taken together, these findings point to a role for iNKT cells in the control of pneumonia as well as in the development of the CD8(+) T cell response during the early stage of acute IAV H3N2 infection.

Defective CD8+ T cell effector function in pathogenic influenza infection (49.7)

Abstract Many questions about CD8+ T cell responses during influenza infection remain unanswered. We therefore examined the development and differentiation of CD8+ T cell memory populations based on specificity and effector function in a mouse model system comparing high and low pathological infections of influenza. Our findings reveal that initial or peak viral titer was not the determining factor in the outcome of disease. Instead, differences in CD8+ T cell effector function were observed for each virus type (high and low pathogenic), and these differences correlated with disease outcome. Further investigation has demonstrated that differences in the airway microenvironment after infection with high and low path infections may significantly affect CD8+ T cell activity. Specifically, increased early production of certain cytokines is associated with highly pathogenic infection. We hypothesize that this altered airway microenvironment results in downmodulation of CTL function via established negative feedback pathways.These phenotypic and functional analyses have revealed distinct effector memory CD8+ T cell populations in the context of influenza infection that have profoundly different capabilities for viral clearance.

Defective CD8 T cell memory generated during latent gammaherpesvirus infection (105.11)

Abstract Antiviral CD8 T cells are essential for protection during murine gammaheresvirus-68 (γHV68) infection. We recently identified a large panel of epitope-specific CD8 T cell responses that were differentially regulated by antigen presentation during the establishment of viral latency, but how these T cell responses are maintained throughout latent infection is unclear. Here we show that recent thymic emigrants are primed during latency, accumulate over time, and can proliferate in response to experimentally-induced viral reactivation. We found that in contrast to ORF6487- and ORF61524-specific responses, CD8 T cells specific for the ORF75c940 epitope primed during latency were deficient in their ability to respond during reactivation. This defect was not a result of impaired generation of ORF75c940-specific cells during latency or a lack of antigen presentation during reactivation, but rather appears to be a consequence of reduced proliferation following stimulation. The finding of epitope-specific differences in proliferative capacity suggests that the functionality of latency-primed responses may be regulated by differential antigen presentation or viral gene expression during latency. These findings have important implications for the development of therapeutic vaccine strategies against latent gammaherpesvirus infections.

ST6Gal I promotes rapid IL-2Rα expression and early proliferation of terminal effector CD8 T cells (46.8)

Abstract ST6Gal I is a glycosyltransferase highly expressed by lymphocytes and cancer cells that catalyzes the addition of α2,6 sialic acid to galactose (Siaα2-6Gal) on N-linked glycoproteins. We discovered that ST6Gal I shows dramatic changes in gene expression during memory CD8 T cell differentiation that corresponds with lectin binding, but the significance of this regulated carbohydrate modification remained a mystery. To identify the significance of these regulated glyco-phenotypic changes, we infected ST6Gal I-/- mice and found that viral-specific cell expansion was impaired. Moreover, defective viral-specific CD8 T cell expansion was due to early intrinsic defects in proliferation of terminal effector cells, whereas memory precursor development was enhanced. We provide direct evidence that loss of ST6Gal I expression by CD8 T cells resulted in delayed surface expression of IL-2Rα in vivo due to impaired IL-2/IL-2R signaling. These results suggest that CD8 T cells regulate ST6Gal I expression to promote proliferation induced by cytokine-dependent signaling.

CD8 + T regulatory cells express the Ly49 Class I MHC receptor and are defective in autoimmune prone B6-Yaa mice

The immune system includes a subpopulation of CD8(+) T cells equipped to inhibit the expansion of follicular T helper (T(FH)) cells, resulting in suppression of autoantibody production and associated lupus-like disease. These CD8(+) T regulatory (Treg) cells recognize Qa-1/peptide complexes on target T(FH) cells and depend on the IL-15 cytokine for development and function. Here we show that these CD8(+) Treg cells express a triad of surface receptors--CD44, CD122, and the class I MHC receptor Ly49--and account for <5% of CD8(+) T cells. Moreover, the development of systemic lupus erythematosus-like disease in B6-Yaa mutant mice is associated with a pronounced defect in CD8(+) Treg cell activity, suggesting that this regulatory subset may represent an effective therapeutic approach to systemic lupus erythematosus-like autoimmune disease.

Immune Evasion by B-cell Lymphoma

Immune Evasion by B-cell Lymphoma

IL-17A–Producing γδT Cells Promote CTL Responses against Listeria monocytogenes Infection by Enhancing Dendritic Cell Cross-Presentation

Interleukin-17A-producing T cells, especially Th17, have been shown to be involved in inflammatory autoimmune diseases and host defense against extracellular infections. However, whether and how IL-17A or IL-17A-producing cells can help protection against intracellular bacteria remains controversial, especially how it regulates the adaptive immunity besides recruitment of neutrophils in the innate immune system. By infecting IL-17A-deficient mice with Listeria monocytogenes, we show in this study that IL-17A is required for the generation of Ag-specific CD8(+) CTL response against primary infection, but not for the generation of memory CD8(+) T cells against secondary challenge. Interestingly, we identify γδT cells, but not conventional CD4(+) Th17 cells, as the main cells for innate IL-17A production during L. monocytogenes infection. Furthermore, γδT cells are found to promote Ag-specific CD8(+) T cell proliferation by enhancing cross-presentation of dendritic cells through IL-17A. Adoptive transfer of Il17a(+/+) γδT cells, but not Il17a(-/-) γδT cells or Il17a(+/+) CD4(+) T cells, were sufficient to recover dendritic cells cross-presentation and defective CD8(+) T cell response in Il17a(-/-) mice. Our findings indicate an important role of infection-inducible IL-17A-producing γδT cells and their derived IL-17A against intracellular bacterial infection, providing a mechanism of IL-17A for regulation of innate and adaptive immunity.

Heat Shock Factor 1 Protects Mice from Rapid Death duringListeria monocytogenesInfection by Regulating Expression of Tumor Necrosis Factor Alpha during Fever

Heat shock factor 1 (HSF1) is a stress-induced transcription factor that promotes expression of genes that protect mammalian cells from the lethal effects of severely elevated temperatures (>42°C). However, we recently showed that HSF1 is activated at a lower temperature (39.5°C) in T cells, suggesting that HSF1 may be important for preserving T cell function during pathogen-induced fever responses. To test this, we examined the role of HSF1 in clearance of Listeria monocytogenes, an intracellular bacterial pathogen that elicits a strong CD8(+) T cell response in mice. Using temperature transponder microchips, we showed that the core body temperature increased approximately 2°C in L. monocytogenes-infected mice and that the fever response was maintained for at least 24 h. HSF1-deficient mice cleared a low-dose infection with slightly slower kinetics than did HSF1(+/+) littermate controls but were significantly more susceptible to challenges with higher doses of bacteria. Surprisingly, HSF1-deficient mice did not show a defect in CD8(+) T cell responses following sublethal infection. However, when HSF1-deficient mice were challenged with high doses of L. monocytogenes, increased levels of serum tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) compared to those of littermate control mice were observed, and rapid death of the animals occurred within 48 to 60 h of infection. Neutralization of TNF-α enhanced the survival of HSF1-deficient mice. These results suggest that HSF1 is needed to prevent the overproduction of proinflammatory cytokines and subsequent death due to septic shock that can result following high-dose challenge with bacterial pathogens.

HLA-E–restricted regulatory CD8+ T cells are involved in development and control of human autoimmune type 1 diabetes

A key feature of the immune system is its ability to discriminate self from nonself. Breakdown in any of the mechanisms that maintain unresponsiveness to self (a state known as self-tolerance) contributes to the development of autoimmune conditions. Recent studies in mice show that CD8(+) T cells specific for the unconventional MHC class I molecule Qa-1 bound to peptides derived from the signal sequence of Hsp60 (Hsp60sp) contribute to self/nonself discrimination. However, it is unclear whether they exist in humans and play a role in human autoimmune diseases. Here we have shown that CD8(+) T cells specific for Hsp60sp bound to HLA-E (the human homolog of Qa-1) exist and play an important role in maintaining peripheral self-tolerance by discriminating self from nonself in humans. Furthermore, in the majority of type 1 diabetes (T1D) patients tested, there was a specific defect in CD8(+) T cell recognition of HLA-E/Hsp60sp, which was associated with failure of self/nonself discrimination. However, the defect in the CD8(+) T cells from most of the T1D patients tested could be corrected in vitro by exposure to autologous immature DCs loaded with the Hsp60sp peptide. These data suggest that HLA-E-restricted CD8(+) T cells may play an important role in keeping self-reactive T cells in check. Thus, correction of this defect could be a potentially effective and safe approach in the therapy of T1D.

Implications of the parent-into-F1 model for human lupus pathogenesis: roles for cytotoxic T lymphocytes and viral pathogens

The central role of CD4 T cells in lupus pathogenesis is well recognized; however, the mechanism by which CD4 T cells lose tolerance and promote humoral autoimmunity remains unclear. This review examines mechanisms elucidated in the parent-into-F1 model of lupus and their possible parallels in human lupus pathogenesis. In the parent-into-F1 model, lupus results from the transfer of normal, foreign reactive CD4 T cells targeted to intrinsically normal F1 B cells. Transfer of normal CD8 T cells prevents lupus, whereas transfer of CD8 T cells with killing defects does not but is correctable with additional in-vivo enhancement of CD8 cytotoxic T lymphocyte (CTL) function. The parent-into-F1 model has two major similarities to Epstein-Barr virus infection: CD4 T-cell-driven polyclonal B-cell hyperactivity and a critical dependence on CD8 CTL for elimination of activated B cells. These similarities are discussed in relation to human lupus pathogenesis. Work in the parent-into-F1 model supports the idea that lupus may result from defective CD8 T-cell function and that therapeutic enhancement of CD8 effectors with selective targeting to autoreactive B cells may be beneficial. Despite strong evidence linking Epstein-Barr virus infection with human lupus, the exact nature of this link requires further study.