Pathogenic T cells in cerebral malaria

Malaria remains a major global health problem and cerebral malaria (CM) is one of the most serious complications of this disease. Recent years have seen important advances in our understanding of the pathogenesis of cerebral malaria. Parasite sequestration, a hallmark of this syndrome, is thought to be solely responsible for the pathological process. However, this phenomenon cannot explain all aspects of the pathogenesis of CM. The use of an animal model, Plasmodium berghei ANKA in mice, has allowed the identification of specific pathological components of CM. Although multiple pathways may lead to CM, an important role for CD8+ T cells has been clarified. Other cells, including platelets, and mediators such as cytokines also have an important role. In this review we have focused on the role of T cells, and discuss what remains to be studied to understand the pathways by which these cells mediate CM.     

The role of CD4 T cell help for CD8 CTL activation

CD4 T cells play an important role in the initiation and persistence of CD8 T cells responses. In this review, we report on and evaluate the mechanisms by which CD4 T cells contribute to activation of CD8 T cells and the signal pathways of the down-streaming events after CD4 T cell help.     

HCV-specific interleukin-21+CD4+ T cells responses associated with viral control through the modulation of HCV-specific CD8+ T cells function in chronic hepatitis C patients

Interleukin-21 (IL-21)+CD4+ T cells are involved in the immune response against hepatitis B virus (HBV) by secreting IL-21. However, the role of IL-21+CD4+ T cells in the immune response against chronic hepatitis C (CHC) virus infection is poorly understood. This study aimed to investigate the role of IL-21+CD4+ T cells in CHC patients and the potential mechanisms. The study subjects included nineteen CHC patients who were grouped by viral load (low, < 10⁶ RNA copies/ml, n = 8; high, > 10⁶ RNA copies/ml, n = 11). The peripheral frequency of HCV-specific IL-21+CD4+ T cells was higher in the low viral load group and was negatively correlated with the serum HCV RNA viral load in all CHC patients. Meanwhile, IL-21+ cells accumulated in the liver in the low viral load group. In vitro, IL-21 treatment increased the expression of proliferation markers and cytolytic molecules on HCV-specific CD8+ T cells. In summary, these findings suggest that HCV-specific IL-21+CD4+ T cells might contribute to HCV control by rescuing HCV-specific CD8+ T cells in CHC patients.     

CD8+T细胞在多发性硬化中的致病性作用

多发性硬化是T细胞介导的自身免疫性疾病。先前对它的研究大多集中在CD4 T细胞的致病和调节性作用上,但是,近几年来越来越多的证据表明CD8 T细胞也参与多发性硬化的病理损伤过程。 CD8 T细胞存在于MS病灶部位,髓鞘抗原特异性CD8 T细胞也从MS患者的血液和脑脊液中分离得到,CD8 T细胞通过直接杀伤或释放细胞因子和趋化因子等间接参与MS的病理过程。本文就近几年关于CD8 T细胞在多发性硬化中的致病性作用的研究进展予以介绍。     

Regulatory T cells constrain the TCR repertoire of antigen‐stimulated conventional CD4 T cells

To analyze the potential role of Tregs in controlling the TCR repertoire breadth to a non‐self‐antigen, a TCRβ transgenic mouse model (EF4.1) expressing a limited, yet polyclonal naïve T‐cell repertoire was used. The response of EF4.1 mice to an I‐Ab‐associated epitope of the F‐MuLV envelope protein is dominated by clones expressing a Vα2 gene segment, thus allowing a comprehensive analysis of the TCRα repertoire in a relatively large cohort of mice. Control and Treg‐depleted EF4.1 mice were immunized, and the extent of the Vα2‐bearing, antigen‐specific TCR repertoire was characterized by high‐throughput sequencing and spectratyping analysis. In addition to increased clonal expansion and acquisition of effector functions, Treg depletion led to the expression of a more diverse TCR repertoire comprising several private clonotypes rarely observed in control mice or in the pre‐immune repertoire. Injection of anti‐CD86 antibodies in vivo led to a strong reduction in TCR diversity, suggesting that Tregs may influence TCR repertoire diversity by modulating costimulatory molecule availability. Collectively, these studies illustrate an additional mechanism whereby Tregs control the immune response to non‐self‐antigens.     

CD8+ T cells exhaustion induced by myeloid‐derived suppressor cells in myelodysplastic syndromes patients might be through TIM3/Gal‐9 pathway

CD8⁺ T cells play a central role in antitumour immunity, which often exhibit ‘exhaustion’ in the setting of malignancy and chronic viral infection due to T cell immunoglobulin and mucin domain 3 (TIM3) and myeloid‐derived suppressor cells (MDSCs). Our team previously found that overactive MDSCs and exhausted TIM3⁺CD8⁺ T cells were observed in myelodysplastic syndromes (MDS) patients. However, it is not obvious whether MDSCs suppress CD8⁺ T cells through TIM3/Gal‐9 pathway. Here, Gal‐9, as the ligand of TIM3, was overexpressed in MDSCs. The levels of Gal‐9 in bone marrow supernatants, serum and culture supernatants of MDSCs from MDS patients were elevated. CD8⁺ T cells from MDS or normal controls produced less perforin and granzyme B and exhibited increased early apoptosis after co‐culture with MDSCs from MDS. Meanwhile, the cytokines produced by CD8⁺ T cells could be partially restored by TIM3/Gal‐9 pathway inhibitors. Furthermore, CD8⁺ T cells produced less perforin and granzyme B after co‐culture with excess exogenous Gal‐9, and the function of CD8⁺ T cells was similarly restored by TIM3/Gal‐9 pathway inhibitors. Expression of Notch1, EOMES (associated with perforin and granzyme B secretion), p‐mTOR and p‐AKT (associated with cell proliferation) was decreased in CD8⁺ T cells from MDS after co‐culture with excess exogenous Gal‐9. These suggested that MDSCs might be the donor of Gal‐9, and TIM3/Gal‐9 pathway might be involved in CD8⁺ T cells exhaustion in MDS, and that TIM3/Gal‐9 pathway inhibitor might be the promising candidate for target therapy of MDS in the future.     

CD40 ligation restores cytolytic T lymphocyte response and eliminates fibrosarcoma in the peritoneum of mice lacking CD4+ T cells

Absence of CD4⁺ T cell help has been suggested as a mechanism for failed anti-tumor cytotoxic T lymphocytes (CTL) response. We examined the requirement for CD4⁺ T cells to eliminate an immunogenic murine fibrosarcoma (6132A) inoculated into the peritoneal cavity. Immunocompetent C3H mice eliminated both single and repeat intraperitoneal (IP) inoculums, and developed high frequency of 6132A-specific interferon-γ (IFNγ)-producing CTL in the peritoneal cavity. Adoptive transfer of peritoneal exudate cells (PEC) isolated from control mice, protected SCID mice from challenge with 6132A. In contrast, CD4 depleted mice had diminished ability to eliminate tumor and succumbed to repeat IP challenges. Mice depleted of CD4⁺ T cells lacked tumor-specific IFNγ producing CTL in the peritoneal cavity. Adoptive transfer of PEC from CD4 depleted mice failed to protect SCID mice from 6132A. However, splenocytes isolated from same CD4 depleted mice prevented tumor growth in SCID mice, suggesting that 6132A-specific CTL response was generated, but was not sustained in the peritoneum. Treating CD4 depleted mice with agonist anti-CD40 antibody, starting on days 3 or 8 after initiating tumor challenge, led to persistence of 6132A-specific IFNγ producing CTL in the peritoneum, and eliminated 6132A tumor. The findings suggest that CTL can be activated in the absence of CD4⁺ T cells, but CD4⁺ T cells are required for a persistent CTL response at the tumor site. Exogenous stimulation through CD40 can restore tumor-specific CTL activity to the peritoneum and promote tumor clearance in the absence of CD4⁺ T cells.Supported in part by grants from Children’s Hospital of Wisconsin Foundation, Society of University Surgeons Foundation, Florence and Marshall Schwid Foundation, Elsa Pardee Foundation, Kathy Duffy Fogarty Fund of the Greater Milwaukee Foundation (JS) and NIH grant RO1-CA-37156 (HS); Andrew Lodge and Ping Yu have contributed equally to this work.     

ThPOK在T细胞分化发育中的作用

ThPOK（T-helper-inducing POZ/Krueppel-like factor）又被称为Zbtb7b、Zfp67、cKrox,隶属于一个很大的转录因子家族——POK家族。ThPOK最初是被认为与Ⅰ型胶原蛋白基因的转录抑制有关,但近年来的研究发现,ThPOK在T细胞分化过程中至关重要,特别是对CD4^＋T细胞的分化发育起着命运决定的核心作用。该文综述了ThPOK在CD4^＋T细胞分化过程中的作用特点及其与另外两种重要转录因子GATA3和Runx3的相互作用关系,并在此基础上阐述了ThPOK在其他T细胞,如iNKT细胞、γδT细胞及效应CD8^＋T细胞中的作用功能。     

Immune responses to p53 in patients with cancer:enrichment in tetramer+ p53 peptide-specific T cells and regulatory T cells at tumor sites

Objective: A majority of human cancers, including head and neck cancer (HNC), overexpress p53. Although T cells specific for wild-type (wt) sequence p53 peptides are detectable in the peripheral blood of patients with HNC, it is unknown whether such T cells accumulate in tumor-involved tissues. Also, the localization of regulatory T cells (Treg) to tumor sites in HNC has not been investigated to date. Methods: Tumor infiltrating lymphocytes (TIL), tumor-involved or non-involved lymph node lymphocytes (LNL) and peripheral blood mononuclear cells (PBMC) were obtained from 24 HLA-A2.1+ patients with HNC. Using tetramers and four-color flow cytometry, the frequency of Treg and CD3+CD8+ T cells specific for wt p53 epitopes as well as their functional attributes were determined. Results: The CD3+CD8+ tetramer+ cell frequency was significantly higher (P<0.001) in TIL than autologous PBMC as was the percentage of CD4+CD25+ T cells (P<0.003). TIL were enriched in FOXp3+, GITR+ and CTLA-4+ Treg. CD8+ TIL had low expression and produced little IFN- after ex vivo stimulation relative to autologous PBMC or PBMC from NC. Conclusions: Anti-wt p53 epitope-specific T cells and Treg preferentially localize to tumor sites in patients with HNC. However, despite enrichment in tumor peptide-specific T cells, the effector cell population (CD3+CD8+) in TIL or PBMC was unresponsive to activation in the tumor microenvironment enriched in Treg.     

Altered frequency of CD8+CD11c+ T cells and expression of immunosuppressive molecules in lymphoid organs of mouse model of colorectal cancer

CD11c is a member of the β2-integrin family typically used to define myeloid dendritic cells (DCs). Recent reports identify CD11c-expressing CD8⁺ T cells as a new subset of CD8⁺ regulatory T cells (Treg). Evidence exists that CD11c⁺CD8⁺ T cells may exert their effector or regulatory functions under different conditions. To date, no studies have addressed the frequency of CD11c⁺ T cells in cancer. Limited evidence exists in terms of expression of immune-checkpoint receptors, programmed cell death protein 1 (PD-1) and T-lymphocyte-associated antigen 4 (CTLA-4), as well as forkhead box P3 (Foxp3) in mouse lymphoid organs. Here, we have assessed CD11c⁺CD8⁺ and CD11c⁺CD4⁺ T cells, Foxp3, PD-1, and CTLA-4 expressing CD4⁺ T cells and CD8⁺ T cells in different tissues from three groups of male BALB/c mice—young, mature, and those with colorectal cancer (CRC). Analysis of CD3⁺CD11c⁺ T cells in the bone marrow (BM), spleen, and lymph nodes (LN) in each group showed a higher percentage of CD3⁺CD11c⁺ T cells in the BM from all groups and in the lymphoid organs of the cancer group compared with the young and mature groups. CD4^low and CD4^high cell fractions in mice BM have different expression patterns for Foxp3 and CTLA-4. We have observed a higher frequency of CD8⁺PD-1⁺ T cells in the BM, spleen, and LN of CRC mice compared with normal mice. T-cell exhaustion is associated with inhibitory receptor PD-1. According to the regulatory roles of CD11c expression in CD8⁺ T cells, we have proposed that the elevated percentage of CD11c, Foxp3, CTLA-4, and PD-1 expressing T cells were associated with immune response dysregulation in CRC.     

Ability of CD8(+) T cell anti-feline immunodeficiency virus activity correlated with peripheral CD4(+) T cell counts and plasma viremia

In the host defense mechanism against feline immunodeficiency virus (FIV) infection, CD8(+) T cells specifically attack virus-infected cells and suppress the replication of the virus in a non-cytolytic manner by secreting soluble factors. In this study, we measured CD8(+) T cell anti-FIV activity in 30 FIV-infected cats. We investigated its relationship with the number of peripheral blood lymphocytes, particularly the CD4(+) T cell and CD8(+) T cell counts, and the relationship between anti-FIV activity and the number of T cells of CD8alpha(+)beta(lo) and CD8alpha(+)beta(-) phenotypes. A clearly significant correlation was observed between anti-FIV activity and the number of CD4(+) T cells. A weaker anti-FIV activity was associated with a greater decrease in the number of CD4(+) T cells. However, there was no significant correlation between anti-FIV activity and the number of B or CD8(+) T cells. Compared with SPF cats, FIV-infected cats had significantly higher CD8alpha(+)beta(lo) T cell and CD8alpha(+)beta(-) T cell counts, but, no significant correlation was observed between these cell counts and anti-FIV activity. This anti-FIV activity significantly correlated with plasma viremia, which was detected in cats with a weak anti-FIV activity. These results suggest that the anti-FIV activity of CD8(+) T cells plays an important role in plasma viremia and the maintenance of CD4(+) T cells in the body. It is unlikely that CD8alpha(+)beta(lo) or CD8alpha(+)beta(-) T cells appearing after FIV infection represent a phenotype of CD8(+) cells with anti-FIV activity.     

The role of virus-specific CD4+ T cells in the control of Epstein-Barr virus infection

Epstein-Barr virus (EBV) establishes lifelong persistent infections in humans and has been implicated in the pathogenesis of several human malignancies. Protective immunity against EBV is mediated by T cells, as indicated by an increased incidence of EBV-associated malignancies in immunocompromised patients, and by the successful treatment of EBV-associated post-transplant lymphoproliferative disease (PTLD) in transplant recipients by the infusion of polyclonal EBV-specific T cell lines. To implement this treatment modality as a conventional therapeutic option, and to extend this protocol to other EBV-associated diseases, generic and more direct approaches for the generation of EBV-specific T cell lines enriched in disease-relevant specificities need to be developed. To this aim, we studied the poorly defined EBV-specific CD4+ T cell response during acute and chronic infection.     

Lung CD8+ T cells in COPD have increased expression of bacterial TLRs

Background

Toll-like receptors (TLRs) on T cells can modulate their responses, however, the extent and significance of TLR expression by lung T cells, NK cells, or NKT cells in chronic obstructive pulmonary disease (COPD) is unknown.

Methods

Lung tissue collected from clinically-indicated resections (n = 34) was used either: (a) to compare the expression of TLR1, TLR2, TLR2/1, TLR3, TLR4, TLR5, TLR6 and TLR9 on lung CD8+ T cells, CD4+ T cells, NK cells and NKT cells from smokers with or without COPD; or (b) to isolate CD8+ T cells for culture with anti-CD3ε without or with various TLR ligands. We measured protein expression of IFN-γ, TNF-α, IL-13, perforin, granzyme A, granzyme B, soluble FasL, CCL2, CCL3, CCL4, CCL5, CCL11, and CXCL9 in supernatants.

Results

All the lung subsets analyzed demonstrated low levels of specific TLR expression, but the percentage of CD8+ T cells expressing TLR1, TLR2, TLR4, TLR6 and TLR2/1 was significantly increased in COPD subjects relative to those without COPD. In contrast, from the same subjects, only TLR2/1 and TLR2 on lung CD4+ T cells and CD8+ NKT cells, respectively, showed a significant increase in COPD and there was no difference in TLR expression on lung CD56+ NK cells. Production of the Tc1 cytokines IFN-γ and TNF-α by lung CD8+ T cells were significantly increased via co-stimulation by Pam3CSK4, a specific TLR2/1 ligand, but not by other agonists. Furthermore, this increase in cytokine production was specific to lung CD8+ T cells from patients with COPD as compared to lung CD8+ T cells from smokers without COPD.

Conclusions

These data suggest that as lung function worsens in COPD, the auto-aggressive behavior of lung CD8+ T cells could increase in response to microbial TLR ligands, specifically ligands against TLR2/1.     

Vitamin E, signalosomes and gene expression in T cells

CD4+T cells from aged humans or mice show significant reductions in IL-2 production upon activation. The resulting decreased proliferation is linked to higher risks of infection in the elderly. Several lines of evidence indicate that intrinsic defects preferentially affecting the naïve subset of CD4+T cells contribute to this reduced IL-2 production. Comparison of the biochemical pathways that transduce activation signals from the T cell receptor to the IL-2 promoter in young and old CD4+T cells has demonstrated age-related impairments at initial molecular events, in particular the phosphorylation of kinases and adapter proteins involved in the formation of signalosomes - complex multiprotein assemblies that provide the framework for effective signal transduction. Confocal microscopy has demonstrated a series of age-related impairments in effective immune synapse formation. Vitamin E can reverse many of these CD4+T cell age-associated defects, including reduced levels of phosphorylation of critical signaling/adapter proteins as well as defective immune synapse formation. Vitamin E also enhances IL-2 production, expression of several cell cycle control proteins, and proliferation. Although the precise mechanisms underlying this effect are not understood, it is possible that this antioxidant lipophilic vitamin can prevent the propagation of polyunsaturated fatty acid peroxidation in the cell membrane, influence the biochemical characteristics of specific lipid bilayer microdomains involved in signal transduction, modulate the activity of kinases/phosphatases, or interact with intracellular receptors.     

Initiation and regulation of CD8+T cells recognizing melanocytic antigens in the epidermis: implications for the pathophysiology of vitiligo

Antigen-specific CD8+T lymphocytes play an important role in defense against cutaneous microbial infection and skin cancer as well as in the pathophysiology of autoimmune skin disease such as lupus erythematodes and vitiligo. We have explored the role of CD8+ cytotoxic T lymphocytes (CTL) in an experimental mouse model of vitiligo, a pigmentation disorder characterized by focal loss of melanocytes in the skin. Using genetic immunization techniques we found that pigment cells in the epidermis can be destroyed by CD8+ T cells specifically recognizing a single H2-Kb-binding peptide derived from the model melanocytic self antigen tyrosinase-related protein 2 (TRP2), a melanosomal enzyme involved in pigment synthesis. Experimental evidence suggests that peripheral tolerance of pigment cell-specific cytotoxic CD8+T cells is regulated in two steps. In the induction phase, stimulation and expansion of these T cells in vivo strictly depends on CD4+ T cell help. In the effector phase, autoimmune destruction of melanocytes in the skin depends on local inflammation facilitating the migration of T cells into the epidermis and supporting effector functions. Our results suggest that accidental stimulation of CD8+ CTL recognizing MHC class I-binding peptides derived from melanocytic proteins in the context of an inflammatory skin disease may play an important role in the pathophysiology of vitiligo. Further investigations will address the role of chemokines, chemokine receptors and adhesion molecules in this experimental system and will reveal the role of keratinocytes and Langerhans cells in regulating cutaneous CD8+ T cell responses.     

CD8+ T Lymphocytes Are the Major Cell Population Involved in the Early Gamma Interferon Response and Resistance to Acute Primary Toxoplasma gondii Infection in Mice

Gamma interferon (IFN-γ) is known to be a major mediator influencing host defense against Toxoplasma (T.) gondii. To evaluate lymphocyte populations involved in this cytokine-mediated early resistance to T. gondii, the effects of in vivo administration of monoclonal antibodies (MAbs) against T-cell subsets and anti-asialo GM1 antibody on the course of infection and IFN-γ response were investigated in mice infected acutely with this parasitic protozoan. A single injection of anti-CD8 MAb on day ?1 or day 4 severely exacerbated the infection, in accordance with a marked suppression of endogenous IFN-γ production. Moreover, the administration of anti-IFN-γ MAb on day 0 but not later than day 4 resulted in a total abrogation of resistance to T. gondii, suggesting that endogenous IFN-γ produced during the first several days of infection is critical for the generation of antitoxoplasmal resistance in mice. In contrast, no significant increase in mortality was observed when injected with either anti-CD4 MAb or anti-asialo GM1 antibody on day ? 1, while these antibodies reduced significantly the ability of mice to produce IFN-γ. Indeed, simultaneous depletion of CD4⁺ and CD8⁺ cells had no greater suppressive effect on host defense and endogenous IFN-γ production than depletion of CD8⁺ cells alone. Together, these results suggest that CD8⁺ T cells play a central role for resolution of acute toxoplasmosis by participating in endogenous IFN-γ production. The possible role of early produced IFN-γ in the development of protective immune response to T. gondii is also discussed.     

Plasma concentrations of transforming growth factor beta 1 in non-progressive HIV-1 infection correlates with markers of disease progression

The human immunodeficiency virus (HIV) infection shows variable rate of disease progression. The underlying biological and molecular mechanisms involved in determining progression of HIV infection are not fully understood. The aims of this study were to determine plasma concentrations of active TGF β 1, Th1 and Th2 cytokines in patients with non-progressive and those with progressive HIV-1 infection, as well as to determine if there is an association of these cytokines to disease progression. In a cross-sectional study of 61 HIV-1 infected individuals categorized according to disease progression as having non-progressive HIV-1 infection (n = 14) and progressive infection (n = 47), plasma levels of active TGF β 1, INF-γ, TNF-α, IL-10, IL-1β, IL-12p70 and IL-13 were compared with HIV uninfected healthy controls (n = 12). Plasma concentration of these cytokines was measured using a highly sensitive luminex200 XMAP assay. Pearson correlation test was used to assess the correlation of cytokines with CD4+ and CD8+ T cells, CD4:CD8 ratio and plasma HIV-1 RNA in the different study groups. Plasma concentrations of TGF β 1 and IL-10 were significantly decreased while IL-1β, IL-12p70 and TNF-α were increased in patients with non-progressive HIV-1 infection compared to patients with progressive infection. Plasma levels of TGF β 1 and IL-10 showed an inverse correlation with CD8+ T cell counts and CD4:CD8 ratios in patients with non-progressive HIV-1 infection, while plasma HIV-1 RNA positively correlated with CD4+ T cell counts. Plasma levels of TNF-α, IL-1β, IL-12p70 and IL-13 positively correlated with CD4+ T cell counts and inversely correlated with plasma HIV-1 RNA, CD8+ T cell count and CD4:CD8 ratio in patients with non-progressive infection. The correlation of cytokines to the state of T-lymphocyte and plasma HIV-1 RNA found in this study may provide insight into the role of cytokines in both progressive and non-progressive HIV-1 infection. Additionally, these findings may have implications for systemic cytokine-based therapies in HIV-1 infection.     

Inducible gene expression with the Tet-on system in CD4+ T cells and thymocytes of mice

CD4+ T cells with their growing list of effector and regulatory subpopulations have vital functions within the immunohematopoietic system. We report here on the first mouse lines that allow temporally and quantitatively controlled expression of transgenes specifically in CD4+ thymocytes and T cells. These were constructed using the Tet-on system. The rtTA2(S)-M2 version of the reverse tetracycline-dependent transactivator was placed under control of all known CD4 regulatory elements. Reporter transgene expression in mice expressing these constructs is highly specific for CD4+ cells, is strictly dependent on the tetracycline derivative doxycycline, and can be regulated by up to five logs depending on the doxycycline concentration. Moreover, we demonstrate that these mice can be used for noninvasive in vivo imaging of a coexpressed luciferase reporter. These new mouse lines should be highly valuable for studying and manipulating numerous aspects of CD4+ T cell development, biology, and function.