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Biomedical subjects

Mark A Exley

Publications and source records attributed to Mark A Exley.

16 recordsLinked to original sources
PubMed2006

Hyporesponsiveness to natural killer T-cell ligand alpha-galactosylceramide in cancer-bearing state mediated by CD11b+ Gr-1+ cells producing nitric oxide.

CD1d-restricted natural killer T (NKT) cells are a potential therapeutic target for cancer, for which several clinical trials have already been reported. NKT cells are specifically activated by a synthetic glycolipid, alpha-galactosylceramide (alpha-GalCer). However, it is known that, in human cancer patients, NKT cells express a degree of hyporesponsiveness to alpha-GalCer. In this study, we have examined the mechanism by which hyporesponsiveness to alpha-GalCer can be induced. In cancer-bearing mice, alpha-GalCer-induced NKT cell expansion, cytokine production, cytotoxicity, and antimetastatic effect in vivo were all significantly impaired. In fact, alpha-GalCer could eliminate metastatic disease in naive animals but failed to protect cancer-bearing mice. CD11b(+) Gr-1(+) cells were particularly increased in cancer-bearing mice and were necessary and sufficient for the suppression of the alpha-GalCer response in a nitric oxide-mediated fashion. Administration of a retinoic acid to cancer-bearing mice reduced the population of CD11b(+) Gr-1(+) cells and effectively restored alpha-GalCer-induced protection. These results show a novel feature of NKT cell function in cancer. Furthermore, our data suggest a new strategy to enhance NKT cell-mediated anticancer immune responses by suppressing CD11b(+) Gr-1(+) cell functions.

Animals↗
PubMed2006

CD1 expression and CD1-restricted T cell activity in normal and tumour-bearing human liver.

CD1d-restricted natural killer T (NKT) cells expressing invariant Valpha14Jalpha18 T cell receptor alpha-chains are abundant in murine liver and are implicated in the control of malignancy, infection and autoimmunity. Invariant NKT cells have potent anti-metastatic effects in mice and phase I clinical trials involving their homologues in humans are ongoing. However, invariant NKT cells are less abundant in human liver ( approximately 0.5% of hepatic T cells) than in murine liver (up to 50%) and it is not known if other hepatic T cells are CD1-restricted. We have examined expression of CD1a, CD1b, CD1c and CD1d mRNA and protein in human liver and evaluated the reactivity of mononuclear cells (MNC) from histologically normal and tumour-bearing human liver specimens against these CD1 isoforms. Messenger RNA for all CD1 isotypes was detectable in all liver samples. CD1c and CD1d were expressed at the protein level by hepatic MNC. CD1d, only, was detectable at the cell surface, but CD1c and CD1d were found at an intracellular location in significant numbers of liver MNC. CD1b was not expressed by MNC from healthy livers but was detectable within MNC in all tumour samples tested. Hepatic T cells exhibited reactivity against C1R cells expressing transfected CD1c and CD1d, but neither CD1a nor CD1b. These cells secreted interferon-gamma (IFN-gamma) but not interleukin-4 (IL-4) upon stimulation. In contrast, similar numbers of peripheral T cells released 13- and 16-fold less IFN-gamma in response to CD1c and CD1d, respectively. CD1c and CD1d expression and T cell reactivity were not altered in tumour-bearing liver specimens compared to histologically normal livers. These data suggest that, in addition to invariant CD1d-restricted NKT cells, autoreactive T cells that recognise CD1c and CD1d and release inflammatory cytokines are abundant in human liver.

Antigens, CD1↗
PubMed2006

The CD1d-binding glycolipid alpha-galactosylceramide enhances humoral immunity to T-dependent and T-independent antigen in a CD1d-dependent manner.

Specific interaction of class II/peptide with the T-cell receptor (TCR) expressed by class II-restricted CD4+ T helper (Th) cells is essential for in vivo production of antibodies reactive with T-dependent antigen. In response to stimulation with CD1d-binding glycolipid, Valpha14+ TCR-expressing, CD1d-restricted natural killer T (NKT) cells may provide additional help for antibody production. We tested the hypothesis that the CD1d-binding glycolipid alpha-galactosylceramide (alpha-GC) enhances production of antibodies reactive with T-dependent antigen in vivo. alpha-GC enhanced antibody production in vivo in a CD1d-dependent manner in the presence of class II-restricted Th cells and induced a limited antibody response in Th-deficient mice. alpha-GC also led to alterations in isotype switch, selectively increasing production of immunoglobulin G2b. Further analysis revealed that alpha-GC led to priming of class II-restricted Th cells in vivo. Additionally, we observed that alpha-GC enhanced production of antibodies reactive with T-independent antigen, showing the effects of NKT cells on B cells independently of Th cells. Our data show that NKT cells have multiple effects on the induction of a humoral immune response. We propose that NKT cells could be exploited for the development of novel vaccines where protective antibody is required.

Animals↗
PubMed2006

Gestation stage-dependent mechanisms of invariant natural killer T cell-mediated pregnancy loss.

Stimulation of CD1d-restricted semiinvariant natural killer T cells by using the CD1d ligand alpha-galactosylceramide (alphaGalCer) induces pregnancy loss in mice through an ill-defined mechanism involving TNF, IFN-gamma, and perforin. In this article, we demonstrate that during early gestation, alphaGalCer efficiently induced pregnancy loss in C57BL/6J and BALB/cJ mice in a perforin-dependent manner. In contrast, during midgestation perforin was no longer required for pregnancy loss. Concomitant with the loss of a perforin requirement at midgestation was the emergence of strain-dependent variations in susceptibility to alphaGalCer-induced pregnancy loss. Whereas pregnant C57BL/6J mice remained susceptible to alphaGalCer at midgestation, pregnant BALB/cJ mice were resistant to its effects. Pregnancy loss during midgestation was correlated with dramatically higher serum cytokine levels, including TNF and IL-2, in the susceptible C57BL/6J strain compared with the resistant BALB/cJ strain. Thus, the stage of gestation defined two distinct mechanisms of pregnancy loss: a perforin-dependent mechanism operating at early gestation and a perforin-independent, cytokine-dominated mechanism operating after midgestation.

Animals↗
PubMed2006

CD1d mediates T-cell-dependent resistance to secondary infection with encephalomyocarditis virus (EMCV) in vitro and immune response to EMCV infection in vivo.

The innate and adaptive immune responses have evolved distinct strategies for controlling different viral pathogens. Encephalomyocarditis virus (EMCV) is a picornavirus that can cause paralysis, diabetes, and myocarditis within days of infection. The optimal innate immune response against EMCV in vivo requires CD1d. Interaction of antigen-presenting cell CD1d with distinct natural killer T-cell ("NKT") populations can induce rapid gamma interferon (IFN-gamma) production and NK-cell activation. The T-cell response of CD1d-deficient mice (lacking all NKT cells) against acute EMCV infection was further studied in vitro and in vivo. EMCV persisted at higher levels in CD1d-knockout (KO) splenocyte cultures infected in vitro. Furthermore, optimal resistance to repeat cycles of EMCV infection in vitro was also shown to depend on CD1d. However, this was not reflected in the relative levels of NK-cell activation but rather by the responses of both CD4(+) and CD8(+) T-cell populations. Repeated EMCV infection in vitro induced less IFN-gamma and alpha interferon (IFN-alpha) from CD1d-deficient splenocytes than with the wild type. Furthermore, the level of EMCV replication in wild-type splenocytes was markedly and specifically increased by addition of blocking anti-CD1d antibody. Depletion experiments demonstrated that dendritic cells contributed less than the combination of NK and NKT cells to anti-EMCV responses and that none of these cell types was the main source of IFN-alpha. Finally, EMCV infection in vivo produced higher levels of viremia in CD1d-KO mice than in wild-type animals, coupled with significantly less lymphocyte activation and IFN-alpha production. These results point to the existence of a previously unrecognized mechanism of rapid CD1d-dependent stimulation of the antiviral adaptive cellular immune response.

Acute Disease↗
PubMed2005

CD1d ligation on human monocytes directly signals rapid NF-kappaB activation and production of bioactive IL-12.

Natural killer T cells (NKT cells) expressing a semi-invariant CD1d-reactive T cell receptor (invariant NKT, iNKT) can be rapidly activated by monocytes or immature dendritic cells (iDCs) bearing a CD1d-presented glycolipid antigen and can in turn stimulate these myeloid cells to mature and produce IL-12. Previous studies have shown that iNKT-produced IFNgamma and CD40 ligand contribute to this dendritic cell maturation. This study demonstrates that CD1d ligation alone, in the absence of iNKT, could rapidly (within 24 h) stimulate production of bioactive IL-12p70 by CD1d+ human peripheral blood monocytes as well as iDCs. IFNgamma alone had no effect, but it markedly enhanced CD1d-stimulated IL-12 production. Monocyte differentiation, as assessed by CD40 and CD1a up-regulation, was also accelerated by CD1d stimulation, consistent with this representing a physiological response. CD1d ligation on the human monocytic cell line THP-1 similarly specifically stimulated IL-12 production. Biochemical studies showed that IL-12 release correlated with rapid phosphorylation of IkappaB, a critical step in NF-kappaB activation. Selective NF-kappaB inhibition blocked this CD1d-stimulated IL-12 production. Finally, CD1d ligation could also enhance IL-12 production in the presence of suboptimal LPS or CD40 stimulation. These findings demonstrate an innate immune signaling function for CD1d and provide a mechanism for the rapid activation of monocytes and iDCs by CD1d-reactive T cells.

Antigens, CD1↗
PubMed2005

Impaired cell surface expression of human CD1d by the formation of an HIV-1 Nef/CD1d complex.

The HIV-1 Nef protein causes a decrease in major histocompatibility complex (MHC) class I and CD4 molecule expression on the cell surface. To determine if Nef can affect components of the innate immune response, we assessed the ability of Nef to alter the cell surface expression of human CD1d. In cells co-expressing CD1d and Nef, a substantial reduction in the cell surface level of CD1d was observed, with a concomitant reduction in the activation of CD1d-restricted NKT cells. Nef had a minimal effect on the cell surface expression of a mutant CD1d molecule in which the last 6 or 10 amino acids of the cytoplasmic tail were deleted. Additionally, it was found that Nef physically interacted with wild-type (but not tail-deleted) CD1d. Therefore, one means by which HIV-1 may be able to establish a foothold in an infected individual is by directly interfering with the functional cell surface expression of CD1d.

Antigens, CD1↗
PubMed2005

CD1d and CD1d-restricted iNKT-cells play a pivotal role in contact hypersensitivity.

CD1d-restricted T-cells are activated by glycolipids presented by the major histocompatibility complex class-Ib molecule CD1d, found on the surface of antigen-presenting cells (APC). This interaction between APC, most notably dendritic cells (DC), and CD1d-restricted T-cells is an important regulatory step in the initiation of adaptive immune responses. It is well known that DC play a crucial role in the induction of contact hypersensitivity (CHS), a frequently studied form of in vivo T-cell-mediated immunity. In this study, we show that CD1d-restricted T-cells are also necessary for CHS, because both wild-type mice treated systemically or topically with CD1d glycolipid antagonists and CD1d-restricted T-cell-null mice have markedly diminished CHS responses. Thus, pharmacologic antagonists of CD1d can be used as effective inhibitors of CHS, a prototype for a variety of delayed-type tissue hypersensitivity responses.

Administration, Topical↗
PubMed2004

Analysis of the major histocompatibility complex in graft rejection revisited by gene expression profiles.

BACKGROUND: The precise role of major histocompatibility complex (MHC) molecules in graft rejection remains incompletely understood. The important role of foreign peptides in the alloimmune response was recently recognized. METHODS: We performed a comparative study of the functions of minor antigens Class I, Class II, and CD1 in murine cardiac allograft rejection by investigating the expression of a large panel of immune and inflammatory genes. To investigate the role of MHC Class II and I, our protocol analyzed allograft recipients deficient in MHC Class II and b2 microglobulin (b2-M), a critical component of the Class I heterodimer. We also included CD1 deficient recipients to differentiate effects in the beta2-M deficient strain due to CD1 deficiency versus the combined inactivation of CD1 and Class I. The serum cytokines tumor necrosis factor (TNF)-alpha interleukin (IL)-6, interferon (IFN)-gamma and IL-1beta were evaluated posttransplant by ELISA. The intragraft expression of 55 chemokines, chemokine receptors, and CD markers were measured by ribonuclease protection assay. The data were analyzed through hierarchical clustering dendrograms and self-organizing maps. RESULTS: The analysis indicates that each gene deficiency induces both the upregulation and the downregulation of distinct subsets of genes and that similar kinetics of rejection can be attributed to different molecular mechanisms. CONCLUSIONS: The study provides novel insights into the role of classical and non-classical MHC molecules in graft rejection.

Animals↗
PubMed2004

Hepatic CD1d expression in hepatitis C virus infection and recognition by resident proinflammatory CD1d-reactive T cells.

A subset of CD161(+)CD56(+/-) NKT cells can recognize glycolipids presented by CD1d and positively or negatively regulate inflammatory responses, including those implicated in several models of hepatitis. CD1d is expressed at very low levels in the healthy liver, but there is a large fraction of CD161(+)CD56(+) NKT cells. There are high levels of nonclassical proinflammatory hepatic CD1d-reactive T cells in hepatitis C virus (HCV) infection. Hepatic inflammatory cells and biliary cells adjacent to portal tract fibrotic areas of HCV-infected donors specifically up-regulated CD1d. A hepatocyte cell line expressing minimal CD1d was efficiently recognized by hepatic CD1d-reactive T cells, suggesting a role for these cells in disease. Hepatic CD1d-reactive T cells from HCV-positive as well as negative donors produced large amounts of IFN-gamma with some IL-13, but only rarely detectable IL-4. We confirmed large numbers of hepatic CD161(+) T cells, lower levels of CD56(+) T cells, and small numbers of classic invariant NKT cells. However, hepatic CD1d-reactivity was not restricted to any of these populations. We suggest virally infected hepatic cells can process potent CD1d-presented liver Ag(s), for surveillance by resident Th1 hepatic CD1d-reactive T cells. This process may be beneficial in acute viral clearance, but in chronic infection could contribute to liver injury.

Acute Disease↗
PubMed2004

To be or not to be NKT: natural killer T cells in the liver.

Much of the hepatology literature to date has focused on the adaptive, antigen-specific response mediated by classical T-cell populations in both the protection and pathogenesis of liver disease. However, the liver is selectively enriched for cells representative of innate immunity, including natural killer T (NKT) cells. In particular, certain CD1d-reactive T cells are present at much higher frequencies in the liver than in the peripheral blood. Although these cells have previously been defined mostly on the basis of phenotypic markers, recent emerging literature regarding NKT cell populations has revealed considerable functional complexity. This review summarizes the recent literature regarding NKT cells, which may have important roles in a variety of liver diseases. Although there is an abundance of literature on the phenotype, distribution, and function of these cells in mice, much less is known about them in human health or liver diseases.

Aged↗
PubMed2003

Phenotypic and functional characterization of long-term cultured rhesus macaque spleen-derived NKT cells.

Natural killer T cells are immunoregulatory cells, which have important roles in tolerance and autoimmunity, as demonstrated primarily in mice and humans. In this study, we define the phenotype and function of Valpha24(+) T cells derived from the spleens of rhesus macaques, a species increasingly used in models of immune tolerance. Valpha24(+) cells were isolated and expanded with monocyte-derived immature dendritic cells in the presence of alpha-galactosylceramide, IL-2, and IL-15. Rhesus NKT cells were stained with mAbs against both Valpha24 and the invariant complementarity-determining region 3 epitope of the human Valpha24/JalphaQ TCR. The cells were CD4, CD8 double negative and expressed CD56. Rhesus NKT cells also exhibited moderate to high expression of CD95, CD45RO, CD11a, and beta(7) integrin, but did not express CD45 RA, CD62L, CCR7, CD28, and other activation, costimulatory molecules (CD69 and CD40L). By intracellular staining, >90% of unstimulated rhesus NKT cells expressed IL-10, but not IFN-gamma. However, the latter was strongly expressed after stimulation. Rhesus NKT secreted large amounts of TGF-beta, IL-13, and IL-6, and modest levels of IFN-gamma, whereas IL-10 secretion was negligible and no detectable IL-4 was observed either intracellularly or in culture supernatants. Functionally, the NKT cells and their supernatants suppressed T cell proliferation in allogeneic MLR. We conclude that long-term cultured rhesus macaque spleen-derived Valpha24(+) T cells are semi-invariant double-negative cells with effector memory phenotype. These cells are semianergic, polarized to a uniquely Th3 > T regulatory-1 regulatory cell phenotype, and have regulatory/suppressive function in vitro.

Animals↗
PubMed2003

CD1d-restricted T cells regulate dendritic cell function and antitumor immunity in a granulocyte-macrophage colony-stimulating factor-dependent fashion.

CD1d-restricted T cells contribute to tumor protection, but their precise roles remain unclear. Here we show that tumor cells engineered to secrete granulocyte-macrophage colony-stimulating factor induce the expansion of CD1d-restricted T cells through a mechanism that involves CD1d and macrophage inflammatory protein 2 expression by CD8 alpha-, CD11c+ dendritic cells (DCs). The antitumor immunity stimulated by vaccination with irradiated, granulocyte-macrophage colony-stimulating factor-secreting tumor cells was abrogated in CD1d- and J alpha 281-deficient mice, revealing a critical role for CD1d-restricted T cells in this response. The loss of antitumor immunity was associated with impaired tumor-induced T helper 2 cytokine production, although IFN-gamma secretion and cytotoxicity were preserved. DCs from immunized CD1d-deficient mice showed compromised maturation and function. Together, these results delineate a role for CD1d-restricted T cell-DC cross talk in the shaping of antitumor immunity.

Animals↗
PubMed2003

Innate immune response to encephalomyocarditis virus infection mediated by CD1d.

CD1d-reactive natural killer T (NKT) cells can rapidly produce T helper type 1 (Th1) and/or Th2 cytokines, can activate antigen-presenting cell (APC) interleukin-12 (IL-12) production, and are implicated in the regulation of adaptive immune responses. The role of the CD1d system was assessed during infection with encephalomyocarditis virus (EMCV-D), a picornavirus that causes acute diabetes, paralysis and myocarditis. EMCV-D resistance depends on IL-12-mediated interferon-gamma (IFN-gamma) production. CD1d-deficient mice, which also lack CD1d-reactive NKT cells, were substantially more sensitive to infection with EMCV-D. Infected CD1d knockout mice had decreased IL-12 levels in vitro and in vivo, and indeed were protected by treatment with exogenous IL-12. IFN-gamma production in CD1d knockout mice was decreased compared with that in wild-type (WT) mice in response to EMCV-D in vitro, although differences were not detected in vivo. Treatment with anti-asialo-GM1 antibody, to deplete NK cells, caused a marked increase in susceptibility of WT mice to EMCV-D infection, whereas CD1d knockout mice were little affected, suggesting that NK-cell-mediated protection is CD1d-dependent. Therefore, these data indicate that CD1d is essential for optimal responses to acute picornaviral infection. We propose that CD1d-reactive T cells respond to early immune signals and function in the innate immune response to a physiological viral infection by rapidly augmenting APC IL-12 production and activating NK cells.

Animals↗
PubMed2002

Cutting edge: Compartmentalization of Th1-like noninvariant CD1d-reactive T cells in hepatitis C virus-infected liver.

Murine intrahepatic lymphocytes (IHL) are dominated by invariant TCR alpha-chain expressing CD1d-reactive NKT cells, which can cause model hepatitis. Invariant NKT (CD56(+/-)CD161(+)) and recently identified noninvariant CD1d-reactive T cells rapidly produce large amounts of IL-4 and/or IFN-gamma and can regulate Th1/Th2 responses. Human liver contains large numbers of CD56(+) NKT cells but few invariant NKT. Compared with matched peripheral blood T cell lines, primary IHL lines from patients with chronic hepatitis C had high levels of CD161 and CD1d reactivity, but the invariant TCR was rare. CD1d-reactive IHL were strikingly Th1 biased. IHL also demonstrated CD1d-specific cytotoxic activity. Hepatocytes and other liver cells express CD1d. These results identify a novel population of human T cells that could contribute to destructive as well as protective immune responses in the liver. CD1d-reactive T cells may have distinct roles in different tissues.

Antigens, CD1↗