NK1.1+ T cell receptor-alpha/beta+ cells: new clues to their origin, specificity, and function

Essential role of LFA-1 in activating Th2-like responses by alpha-galactosylceramide-activated NKT cells

NKT cells produce large amounts of cytokines associated with both the Th1 (IFN-gamma) and Th2 (IL-4) responses following stimulation of their invariant Valpha14 Ag receptor. The role of adhesion molecules in the activation of NKT cells by the Valpha14 ligand alpha-galactosylceramide (alpha-GalCer) remains unclear. To address this issue, LFA-1-/- (CD11a-/-) mice were used to investigate IL-4 and IFN-gamma production by NKT cells following alpha-GalCer stimulation. Intriguingly, LFA-1-/- mice showed increased IL-4, IL-5, and IL-13 production and polarized Th2-type responses in response to alpha-GalCer in vitro and in vivo. Furthermore, the Th2-specific transcription factor GATA-3 was up-regulated in alpha-GalCer-activated NKT cells from LFA-1-/- mice. These results provide the first genetic evidence that the adhesion receptor LFA-1 has a crucial role in Th2-polarizing functions of NKT cells.

Increase in hepatic NKT cells in leukocyte cell-derived chemotaxin 2-deficient mice contributes to severe concanavalin A-induced hepatitis

Leukocyte cell-derived chemotaxin 2 (LECT2) was originally identified for its possible chemotactic activity against human neutrophils in vitro. It is a 16-kDa protein that is preferentially expressed in the liver. Its homologues have been widely identified in many vertebrates. Current evidence suggests that LECT2 may be a multifunctional protein like cytokines. However, the function of LECT2 in vivo remains unclear. To elucidate the role of this protein in vivo, we have generated LECT2-deficient (LECT2(-/-)) mice. We found that the proportion of NKT cells in the liver increased significantly in LECT2(-/-) mice, although those of conventional T cells, NK cells, and other cell types were comparable with those in wild-type mice. Consistent with increased hepatic NKT cell number, the production of IL-4 and IFN-gamma was augmented in LECT2(-/-) mice upon stimulation with alpha-galactosylceramide, which specifically activates Valpha14 NKT cells. In addition, NKT cell-mediated cytotoxic activity against syngeneic thymocytes increased in hepatic mononuclear cells obtained from LECT2(-/-) mice in vitro. Interestingly, the hepatic injury was exacerbated in LECT2(-/-) mice upon treatment with Con A, possibly because of the significantly higher expression of IL-4 and Fas ligand. These results suggest that LECT2 might regulate the homeostasis of NKT cells in the liver and might be involved in the pathogenesis of hepatitis.

Suppression of hepatocellular carcinoma growth via oral immune regulation towards tumor-associated antigens is associated with increased NKT and CD8+ lymphocytes

BACKGROUND

Oral immune regulation towards viral proteins was previously shown to modulate the anti-HBV immune response. Adoptive transfer of orally immunomodulated lymphocytes suppressed the growth of hepatocellular carcinoma (HCC) expressing HBsAg in athymic mice. NKT lymphocytes play a role in the defense against tumor growth.

AIM

To evaluate the effect of oral immune regulation towards HCC-associated antigens or HBV proteins on growth of HBsAg-expressing HCC, and to determine the role of NKT lymphocytes in immune modulation.

METHODS

Sublethally irradiated athymic Balb/c mice were injected with 10(7) human hepatoma cells followed 10 days later by transplantation of 2 x 10(6) splenocytes from naive donor mice. Immune modulation was performed via feeding of HCC-extracted proteins or HBV antigens (HBsAg + Pre S1 + Pre S2). The control group was fed with bovine serum albumin (BSA). Mice were followed for survival, tumor volume, and serum alpha-fetoprotein levels. To determine the role of NKT cells in tumor suppression, cytokine expression and FACS analysis for CD4+, CD8+, and NK1.1+ T lymphocyte subsets were performed.

RESULTS

Oral immune regulation towards HCC-extracted proteins induced complete tumor suppression in recipient mice. Mortality rates were 0% in HCC-immune-regulated mice, compared with an 80% mortality rate using HBV antigens and a 100% mortality rate in control mice. Oral immune regulation towards HCC prevented weight loss. No visible tumor mass was observed in orally immune-regulated mice as compared with 112 mm(3) in controls. Serum alphaFP levels were 0.9, 378 and 1,358 ng/ml in HCC, HBV immune-regulated and controls, respectively. Immune regulation towards HCC antigens significantly increased the NK1.1+ T lymphocytes/CD4+ and CD8+/CD4+ ratios. IFNgamma production increased two-fold.

CONCLUSION

Oral immune regulation towards HCC antigens effectively enhanced the anti-tumor immune response, thus suppressing the growth of HCC in mice. This effect was associated with an increased NKT,CD8+/CD4+ lymphocyte ratio and may be mediated via enhancement of IFNgamma production.

Immunoregulatory defects of V alpha 24V+ beta 11+ NKT cells in development of Wegener's granulomatosis and relapsing polychondritis

The frequency of either CD4(-)8(-) (double negative; DN) or CD4(+) V alpha 24(+)V beta 11(+) NKT cells, the expression of CD1d and the binding of CD1d-tetramer loaded with alpha-galactosylceramide (alpha-GalCer) to NKT cells were analysed in peripheral blood mononuclear cells (PBMCs) of patients with Wegener's granulomatosis (WG), relapsing polychondritis (RP) and healthy subjects (HS). DN and CD4(+) V alpha 24(+)V beta 11(+) NKT cells as well as CD1d-alpha-GalCer tetramer-positive NKT cells, were significantly decreased in number in both WG and RP patients compared to those from HS. When cytokine profiles were analysed in these PBMCs upon stimulation with phorbol ester and calcium ionophore, CD4(+) T cells from patients with WG and RP exhibited a Th1 bias, whereas CD4(+) NKT cells from WG patients in remission showed a Th2 bias. These findings suggest that NKT cells (especially CD4(+) NKT cells) play a regulatory role in Th1 autoimmunity in patients with WG and RP. The reduction in NKT cell counts appears to be associated with the low responsiveness to alpha-GalCer. The dysfunction of NKT cells to recognize ligands such as alpha-GalCer may also contribute to the defects observed in NKT cells from WG and RP patients.

Positive and negative selection of T cell repertoires during differentiation in allogeneic bone marrow chimeras

T cells acquire immune functions during expansion and differentiation in the thymus. Mature T cells respond to peptide antigens (Ag) derived from foreign proteins when these peptide Ag are presented on the self major histocompatibility complex (MHC) molecules but not on allo-MHC. This is termed self-MHC restriction. On the other hand, T cells do not induce aggressive responses to self Ag (self-tolerance). Self-MHC restriction and self-tolerance are not genetically determined but acquired a posteriori by positive and negative selection in the thymus in harmony with the functional maturation. Allogeneic bone marrow (BM) chimera systems have been a useful strategy to elucidate mechanisms underlying positive and negative selection. In this communication, the contribution of BM chimera systems to the investigation of the world of T-ology is discussed.

The role of intrahepatic CD8+ T cell trapping and NK1.1+ cells in liver-mediated immune regulation

The liver was previously suggested as a site of lymphocyte clearance. Liver-associated lymphocytes that express NK1.1 marker (NKT LAL) play a role in immune modulation.

AIM

To determine the role of the liver and of NKT LAL in determining the CD4+/CD8+ balance during tolerance induction.

METHODS

Colitis was induced in C57 mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Immune tolerance was induced via five oral feedings of colitis-extracted proteins (CEP) from TNBS-colitis colonic wall, starting on the day of colitis induction (group A). Control mice were fed with BSA (group B). To determine the role of NKT cells in immune modulation, NK1.1 depletion was performed in nonfed (group C) and fed (group D) mice. To further evaluate the role of NKT cells in this model, mice in group E were tolerized following NKT depletion. To determine the effect of NKT depletion in a tolerized environment, tolerized mice in group F were NKT depleted following tolerance induction. Peripheral and intrahepatic NK1.1+ and CD4+/CD8+ T cells were determined in all groups. Colitis was assessed by standard clinical and histologic scores. Serum cytokines levels were measured by ELISA.

RESULTS

Oral tolerance induction led to a marked alleviation of colitis as manifested by a significant improvement of the clinical, macroscopic, and microscopic scores of colitis (group A vs. group B). NK1.1+ depletion without tolerance induction had a favorable effect on colitis (C). Depletion of NKT LAL prevented the ability to induce tolerance (group D). However, induction of tolerance following NK1.1+ depletion, and NK1.1+ depletion following tolerance induction led to a marked improvement of colitis (groups E and F). Tolerance induction led to a significant increase in NKT LAL numbers. The peripheral CD4+/CD8+ ratio increased up to 3-fold in tolerized vs. non-tolerized mice. A similar increase was observed in NKT-depleted healthy mice in groups C, E, and F (P < 0.005). In contrast, NK1.1+ depletion in the presence of antigen in the bowel led to a reverse effect with a significant decrease in the peripheral CD4+/CD8+ ratio. An opposite effect was observed in the intrahepatic CD4+/CD8+. The peripheral/intrahepatic CD4+/CD8+ ratio increased significantly in tolerized and in healthy mice (A, D, E, F, P < 0.005). In contrast, NK1.1+ depleted fed mice in group C manifested a marked decrease in the peripheral/intrahepatic CD4+/CD8+ ratio. Induction of tolerance led to a marked increase in the IL-10/interferon gamma (IFNgamma) and IL-4/IFNgamma ratios.

CONCLUSIONS

In the experimental colitis model, the liver is an important site for CD8+ accumulation during tolerance induction in a process that is independent of NK1.1+ cells. NK1.1+ cells play a dual role in the pro/anti-inflammatory balance. In the presence of antigen, these lymphocytes may be accountable for keeping an anti-inflammatory lymphocyte balance. However, in the absence of antigen, they may induce a pro-inflammatory shift.

The mouse natural killer T cell-associated antigen recognized by U5A2-13 monoclonal antibody is intercellular adhesion molecule-1

Natural Killer T (NKT) cells in mice are generally defined as NK1.1(+) T cells, although NK1.1 antigen is expressed only in C57BL/6 and related strains. This has precluded investigations of other strains. To find a novel NKT cell surface marker, we generated a monoclonal antibody (mAb), U5A2-13, which recognizes phenotypically and functionally similar populations to NKT cells in naïve mice irrespective of strain. Here, by using a COS-7 expressional cloning system, we molecularly cloned a cDNA encoding a protein reactive with the U5A2-13 mAb and then identified it as intercellular adhesion molecule-1 (ICAM-1). Importantly, the U5A2-13 mAb did not stain hepatic mononuclear cells from ICAM-1 gene disrupted mice. Furthermore, Pepscan method disclosed that the discontinuous epitope for U5A2-13 mAb is composed of three loops located in extracellular domain two of ICAM-1. Overall, U5A2-13, a mAb originally established for mouse NKT cells, recognizes a novel conformational epitope of ICAM-1.

Induction of CD4+ murine natural killer T-like cells by immunization with syngeneic thymoma expressing embryonic alpha-fetoprotein

In embryo, before the establishment of acquired immunity, a variety of embryonic antigens like alpha-fetoprotein (AFP) are produced and secreted in the sera, which rapidly disappear after the birth. Such embryonic antigens sometimes reappear from various tumor cells and decrease in the case of remission, indicating embryonic antigens may alert immune system to control tumors. In the present study, to examine the evoked immune responses against the tumors expressing embryonic antigen, we administered AFP-gene-transfected EL4 cells into syngeneic C57BL/6 mice and established a killer line against the tumor cells. To our surprise, the killer line was CD4+ NK1.1+, natural killer T (NKT)-like cells and eliminated not only AFP-expressing EL4 but YAC-1 cells. Moreover, the established line uniformly expressed Vbeta11 and secreted IL-4, IL-10, IL-13, and IFN-gamma. In vivo inoculation of the line markedly reduced the tumor growth in SCID mice, suggesting novelty of the NKT-like line for tumor surveillance.

Virus dynamics and immune responses during treatment in patients coinfected with hepatitis C and HIV

Mathematical modeling of the biological effect of interferon on virus decay permits the quantification of the efficacy (epsilon) of blocking virion production in different patient populations. The viral dynamic and immunologic responses of hepatitis C virus (HCV) infection to daily interferon therapy were characterized in twelve patients co-infected with human immunodeficiency virus (HIV). Three out of the twelve patients (25%) achieved an early viral response, a two-log reduction in HCV RNA by week 12. The mean epsilon of IFN-alpha in blocking HCV and HIV production were 72% and 74%, respectively. For HCV epsilon was highest (97%) in the one patient who had a sustained viral response, while it was reduced in the other two patients (68% and 77%). Baseline HCV RNA and the number of CD3+CD56+16+ cells were inversely related (r = -0.89, p = 0.03), and baseline HCV-specific immune responses were significantly higher in the three patients with 2-log viral load reductions. These data suggest that: 1) interferon efficacy at blocking virion production is correlated with treatment outcome in HIV/HCV co-infected patients, 2) that immunodeficient patients can respond to standard IFN-alpha, 3) that both innate and adaptive immune responses may be important determinants of HCV RNA decline in response to interferon.

NKT cells enhance CD4+ and CD8+ T cell responses to soluble antigen in vivo through direct interaction with dendritic cells

Modification in the function of dendritic cells (DC), such as that achieved by microbial stimuli or T cell help, plays a critical role in determining the quality and size of adaptive responses to Ag. NKT cells bearing an invariant TCR (iNKT cells) restricted by nonpolymorphic CD1d molecules may constitute a readily available source of help for DC. We therefore examined T cell responses to i.v. injection of soluble Ag in the presence or the absence of iNKT cell stimulation with the CD1d-binding glycolipid alpha-galactosylceramide (alpha-GalCer). Considerably enhanced CD4(+) and CD8(+) T cell responses were observed when alpha-GalCer was administered at the same time as or close to OVA injection. This enhancement was dependent on the involvement of iNKT cells and CD1d molecules and required CD40 signaling. Studies in IFN-gammaR(-/-) mice indicated that IFN-gamma was not required for the adjuvant effect of alpha-GalCer. Consistent with this result, enhanced T cell responses were observed using OCH, an analog of alpha-GalCer with a truncated sphingosine chain and a reduced capacity to induce IFN-gamma. Splenic DC from alpha-GalCer-treated animals expressed high levels of costimulatory molecules, suggesting maturation in response to iNKT cell activation. Furthermore, studies with cultured DC indicated that potentiation of T cell responses required presentation of specific peptide and alpha-GalCer by the same DC, implying conditioning of DC by iNKT cells. The iNKT-enhanced T cell responses resisted challenge with OVA-expressing tumors, whereas responses induced in the absence of iNKT stimulation did not. Thus, iNKT cells exert a significant influence on the efficacy of immune responses to soluble Ag by modulating DC function.

Inhibition of CD1d activation suppresses septic mortality: a role for NK-T cells in septic immune dysfunction

BACKGROUND

Studies indicate that following septic insult there is development of generalized immune dysfunction in T cells, B cells and phagocytes, which is thought to contribute to morbidity and mortality. Specifically, there is a shift in the lymphocytes of septic animals toward an increased release of Th2 cytokines. NK-T cells have been shown to contribute to propagation of the Th2 response. The influence of NK-T cells on the immune response to septic challenge is poorly understood. In this study, we examine whether NK-T cells contribute to the immune dysfunction seen following the onset of polymicrobial sepsis, as produced by cecal ligation and puncture (CLP).

MATERIALS AND METHODS

Male 129S1/SvImJ mice were pretreated with either rat IgG (isotypic control) or monoclonal antibody to CD1d (clone 1B1) (0.5 mg), which blocks signaling/antigen presentation via the CD1d cell surface receptor, thereby, ablating the activation and differentiation of the NK-T cells. Septic survival with and without anti-CD1d (CLP/CD1d) pretreatment was assessed. Mice sacrificed 24 h after CLP were assessed for change in splenic %NK-T cell (via flourescense activated cell sector) and for splenic, hepatic, and lymphoid/macrophage production of pro-inflammatory or anti-inflammatory cytokines (via enzyme-linked immunosorbent assay).

RESULTS

Administration of anti-CD1d reduced septic mortality 35% at 6-10 d (n = 23 mice/group) (P <.05). There was a consistent increase in the %CD3(+) NK1.1(+) cell population (NK-T cells) in septic mice (1.706%), which was markedly suppressed by pretreatment with anti-CD1d (0.592%). IL-6 and IL-10 levels were suppressed by anti-CD1d in the spleen and blood.

CONCLUSIONS

Together these findings imply not only that NK-T cells may play a role in mediating the immune suppression seen in bacterial sepsis, but that inhibition of their activation promotes survival to septic challenge.

Immunoregulatory Cells for Transplantation Tolerance and Graft-versus-Leukemia Effect

Various immunoregulatory cells that inhibit graft-versus-host disease (GVHD) and induce the graft-versus-leukemia (GVL) effect are found after allogeneic hematopoietic stem cell transplantation. These cells comprise CD4+CD25+ regulatory T-cells, regulatory dendritic cells (rDCs), gamma(delta) T-cells, natural killer (NK) T-cells, and NK cells and T-cells with inhibitory NK receptors. Although the first 4 types of cells effectively inhibit GVHD in animal models, with rDCs showing an inhibitory effect on GVHD in humans as well, the GVL effect was observed only in rDCs. Additional analyses are required to determine whether these cells can inhibit GVHD and exert the GVL effect in humans. In contrast, NK cells and T-cells with inhibitory NK receptors have been shown in humans to possess a suppressive activity against GVHD while preserving the GVL effect. These results indicate that immunoregulatory cells may be used to modulate GVHD and the GVL effect in clinical settings.

NKT and CD8 lymphocytes mediate suppression of hepatocellular carcinoma growth via tumor antigen-pulsed dendritic cells

Dendritic cells (DCs) are antigen presenting cells that play a role in T-cell activation. Liver-associated natural killer T lymphocytes (NKTs) are a unique subset of lymphocytes that may be important in antitumor immunity. Hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) expresses hepatitis B virus surface antigen (HBsAg) on its cell surface and may serve as a tumor-associated antigen. The aim of the study was to evaluate the antitumor effect of DC pulsed with tumor or viral-associated antigens in HBV-expressing HCC in mice and to determine the role of NKT lymphocytes in this process. Balb/c mice were sublethally irradiated and transplanted with Hep3b HCC cell line, followed by transplantation of naive splenocytes. DCs were separated using CD11c beads and pulsed with HBV-enveloped proteins (group A), HCC cell lysate (group B), or BSA (control group C). Mice were followed for survival and tumor size. To determine the mechanism of the antitumor effect, intrasplenic and intrahepatic lymphocyte subpopulations were analyzed by FACS for NKT, CD4 and CD8 markers. Tumor-associated antigens-specific IFNgamma ELISPOT, T-cell proliferation assays and serum cytokine analysis were performed. Treatment with tumor-associated antigen-pulsed DC significantly improved survival (40% and 50% as compared with 0% in groups A, B, and control group C, respectively; p < 0.005). Tumor size decreased to 12.8 +/- 0.4 and 0 from 60.4 +/- 0.9 mm(3) in groups A, B, and control group C, respectively (p < 0.005). Adoptive transfer of HBV or Hep3b-associated antigens-pulsed DC induced a 6-fold increase in peripheral CD8(+) lymphocytes (from 1% in control mice to 6% and 5.5% in groups A and B, respectively), along with a decrease in CD4(+) lymphocytes (from 3.5% in controls to 1.4% and 2.3% in A and B, respectively; p < 0.005). The CD8(+)/CD4(+) ratio increased from 0.28 in controls to 4.28 and 2.39 in groups A and B, respectively (p < 0.005). Intrasplenic NKT cells increased from 7% in control mice to 7.98% and 14.6% in groups A and B, respectively. In contrast, an opposite shift was observed inside the liver. Intrahepatic lymphocyte analysis showed a marked increase in CD4(+) and a decrease in CD8(+) lymphocytes in treated groups. The intrahepatic CD4(+) number increased from 0.5% in controls to 2.15% and 25.8% in groups A and B, respectively (p < 0.005). In contrast, a significant decrease in the intrahepatic CD8(+) numbers was observed (from 7% in controls to 1.0% and 2.4% in groups A and B, respectively; p < 0.005). A significant increase was noted in HBV-specific IFNgamma spot-forming T-cell colonies from 0.0 to 8.8 +/- 1.7 and 1.8 +/- 2.9 in groups C, A, and B, respectively (p < 0.005). Similarly, a significant increase in the HBV-specific T-cell stimulation index, from 0.8 +/- 0.2 to 7.2 +/- 0.4, in groups C and B, respectively, was noted (p < 0.002). IFNgamma and IL12 serum levels increased significantly in treated groups. IFNgamma and IL12 serum levels increased to 380 +/- 30 and 400 +/- 20, and 960 +/- 40 and 760 +/- 60 in groups A and B, compared with 150 +/- 16 and 490 +/- 40 pg/ml in control mice (p < 0.005). Tumor antigen-pulsed DCs effectively suppressed the growth of hepatocellular carcinoma in mice. This effect was associated with enhanced NKT and CD8(+) lymphocyte function and augmentation of the antitumor/antiviral-specific IFNgamma production.

Multiple T cell subsets control Francisella tularensis LVS intracellular growth without stimulation through macrophage interferon gamma receptors

A variety of data suggest that in vivo production of interferon (IFN)-gamma is necessary, but not sufficient, for expression of secondary protective immunity against intracellular pathogens. To discover specific IFN-gamma-independent T cell mediated mechanisms, we took advantage of an in vitro culture system that models in vivo immune responses to the intracellular bacterium Francisella tularensis live vaccine strain (LVS). LVS-immune lymphocytes specifically controlled 99% of the growth of LVS in wild-type murine bone marrow-derived macrophages. Surprisingly, LVS-immune lymphocytes also inhibited LVS intracellular growth by as much as 95% in macrophages derived from IFN-gamma receptor knockout (IFNgammaR KO) mice. CD8+ T cells, and to a lesser degree CD4+ T cells, controlled LVS intracellular growth in both wild-type and IFNgammaR KO macrophages. Further, a unique population of Thy1+alphabeta+CD4-CD8- cells that was previously suggested to operate during secondary immunity to LVS in vivo strongly controlled LVS intracellular growth in vitro. A large proportion of the inhibition of LVS intracellular growth in IFNgammaR KO macrophages by all three T cell subsets could be attributed to tumor necrosis factor (TNF) alpha. Thus, T cell mechanisms exist that control LVS intracellular growth without acting through the IFN-gamma receptor; such control is due in large part to TNF-alpha, and is partially mediated by a unique double negative T cell subpopulation.

Valpha24+ natural killer T-cell responses against T-acute lymphoblastic leukaemia cells: implications for immunotherapy

Human Valpha24+ natural killer T (NKT) cells correspond to mouse Valpha14+ NKT cells, both cell types use an invariant T-cell receptor-alpha chain and are activated by glycolipids in a CD1d-dependent manner. Mouse Valpha14+ NKT cells have been reported to have an antitumour effect in vivo. Human Valpha24+ NKT cells can kill a proportion of tumour cells in a CD1d-dependent manner in vitro. We report here that many human leukaemic T-cell lines express CD1d and can be directly killed by Valpha24+ NKT cells. This killing activity was enhanced in the presence of alpha-galactosylceramide (alpha-GalCer), a ligand of Valpha24+ NKT cells. Moreover, primary leukaemic T cells from five of eight T-cell acute lymphoblastic leukaemia (T-ALL) patients expressed CD1d and were good targets of Valpha24+ NKT cells. This cytotoxicity was increased in the presence of alpha-GalCer. Our results suggest that T-ALL is a good candidate for Valpha24+ NKT-cell-based immuno-cell therapy.

V alpha 24+ natural killer T cells are markedly decreased in atopic dermatitis patients

Atopic dermatitis (AD) is a common inflammatory skin disease. In AD, cytokines such as interleukin (IL)-4 or interferon (IFN)-gamma are considered to affect the disease status. Recently, human V alpha 24(+) natural killer T (NKT) cells have been found to produce large amounts of IL-4 and IFN-gamma. Thus there is a possibility that the proportion of V alpha 24(+) NKT cells modifies the AD status. In this study, we examine the proportion of the V alpha 24(+)/V beta 11(+) cells that composes the V alpha 24(+) NKT cells in peripheral blood mononuclear cells (PBMCs) from 71 healthy donors (HDs) and 31 AD patients. Because CD4(-) and CD4(+) NKT subsets show different cytokine production patterns concerning IL-4, these two subsets are evaluated. Our results have shown that the proportion of the V alpha 24(+) NKT cells is markedly reduced in AD patients. In addition, the CD4(-) V alpha 24(+) NKT subset has a tendency to be more reduced than the CD4(+) V alpha 24(+) NKT subset. Moreover, the proportion of CD4(-) V alpha 24(+) NKT(+) cells and Th2 deviation of Th1/Th2 balance is inversely correlated. These observations may contribute to the understanding of the mechanism involved in AD.

CD1d-expressing dendritic cells but not thymic epithelial cells can mediate negative selection of NKT cells

Natural killer T (NKT) cells are a unique immunoregulatory T cell population that is positively selected by CD1d-expressing thymocytes. Previous studies have shown that NKT cells exhibit autoreactivity, which raises the question of whether they are subject to negative selection. Here, we report that the addition of agonist glycolipid alpha-galactosylceramide (alpha-GalCer) to a fetal thymic organ culture (FTOC) induces a dose-dependent disappearance of NKT cells, suggesting that NKT cells are susceptible to negative selection. Overexpression of CD1d in transgenic (Tg) mice results in reduced numbers of NKT cells, and the residual NKT cells in CD1d-Tg mice exhibit both an altered Vbeta usage and a reduced sensitivity to antigen. Furthermore, bone marrow (BM) chimeras between Tg and WT mice reveal that CD1d-expressing BM-derived dendritic cells, but not thymic epithelial cells, mediate the efficient negative selection of NKT cells. Thus, our data suggest that NKT cells developmentally undergo negative selection when engaged by high-avidity antigen or abundant self-antigen.

Increased expansion of V alpha 24+ T cells derived from G-CSF-mobilized peripheral blood stem cells as compared to peripheral blood mononuclear cells following alpha-galactosylceramide stimulation

In the present study, unpurified peripheral blood mononuclear cells (PBMCs) from various sources, including steady-state blood (normal donors) and granulocyte colony-stimulating factor (G-CSF)-mobilized blood (cancer patients and normal donors) (G-PBSC), were cultured in RPMI-1640 in the presence of IL-2 and alpha-galactosylceramide (alpha-GalCer) to expand V alpha 24(+) T cells, and their expansion kinetics were compared. G-CSF-mobilized cells showed markedly higher expansion potential (350-fold expansion of V alpha 24(+) T cells, regardless of whether the cells were from cancer patients or normal donors) than steady-state cells (15-fold expansion, compared to the initial inoculums) (n = 5, P < 0.01). We also confirmed that the CD14(-) fraction of G-PBSCs contained a large number of precursors of V alpha 24(+) T cells, compared to PBSCs, as well as a large number of CD14(+) cells, which assist V alpha 24(+) T cell proliferation. Our simple and practical procedure, which eliminates complicated cell manipulation (including cell purification), produces efficient expansion of V alpha 24(+) T cells when G-CSF-mobilized blood cells are cultured with alpha-GalCer.

Expansion of unconventional T cells with natural killer markers in malaria patients

Immunological states during human malarial infection were examined. In parallel with parasitemia and anemia, granulocytosis was induced in the blood of patients, especially those infected with Plasmodium (P.) falciparum. At that time, the level of lymphocytes remained unchanged or slightly increased in the blood. However, the distribution of lymphocyte subsets was modulated, showing that the proportion of CD56(+)T cells, CD57(+)T cells, and gammadeltaT cells (i.e. all unconventional T cells) had increased in patients infected with P. falciparum or P. vivax. This phenomenon occurred at the early phase of infection and disappeared in the course of recovery. The data from patients with multiple attacks of P. vivax infection showed that there was no augmentation of these responses. In adult cases, the increase in the proportion of unconventional T cells seemed to closely parallel disease severity. However, all these responses were weak in children, even those infected with P. falciparum. In conjunction with accumulating evidence from mouse malaria experiments, the present results suggest that the immunological state induced by malarial infection might mainly be an event of unconventional T cells and that the immunological memory might not be long-lasting, possibly due to the properties of unconventional T cells.

Total lymphoid irradiation nonmyeloablative preconditioning enriches for IL-4-producing CD4+-TNK cells and skews differentiation of immunocompetent donor CD4+ cells

Preconditioning with the nonmyeloablative regimen total lymphoid irradiation (TLI) before hematopoietic cell transplantation facilitates the establishment of mixed chimerism and protects against graft-versus-host disease. We reported that the development of mixed chimerism requires interleukin (IL)-4 and is associated with increased host anti-donor TH2 cells, but the effect of TLI on the differentiation of immunocompetent donor cells has not been investigated. To examine the extent to which TLI preconditioning influences donor T cells, we measured responses of transgenic CD4+cells specific for ovalbumin peptide (OVA-Tg) following in vivo and in vitro antigen stimulation in a TLI-preconditioned environment. OVA-Tg cells that were adoptively transferred into TLI-preconditioned mice that express cross-reactive antigens produced more IL-4 and less interferon-gamma and IL-2 than controls when stimulated with OVA peptide one week later. OVA-Tg primed in vitro with spleen from TLI-preconditioned mice generated more TH2 and fewer TH1 cells when stimulated in recall enzyme-linked immunosorbent spot (ELISPOT) assays with OVA peptide. Naive OVA-Tg up-regulated CD69 and CD25 normally following stimulation with OVA peptide in the presence of spleen from TLI-preconditioned mice, but proliferated less and secreted less IL-2 than controls. Surprisingly, naive OVA-Tg secreted IL-4 in primary cultures that were stimulated with OVA peptide in the presence of spleen from TLI-preconditioned mice. This response depends on CD4+cells from TLI-spleen, which constitutively produce IL-4 and are composed primarily of CD4+-natural killer T (TNK) cells. Thus, TLI preconditioning enriches for IL-4-secreting and TNK-like CD4+cells that may function in the protection from graft-versus-host disease by redirecting the differentiation of immunocompetent donor CD4+cells toward TH2 and away from pathogenic TH1 cells.

Human invariant V alpha 24-J alpha Q TCR supports the development of CD1d-dependent NK1.1+ and NK1.1- T cells in transgenic mice

A sizable fraction of T cells expressing the NK cell marker NK1.1 (NKT cells) bear a very conserved TCR, characterized by homologous invariant (inv.) TCR V alpha 24-J alpha Q and V alpha 14-J alpha 18 rearrangements in humans and mice, respectively, and are thus defined as inv. NKT cells. Because human inv. NKT cells recognize mouse CD1d in vitro, we wondered whether a human inv. V alpha 24 TCR could be selected in vivo by mouse ligands presented by CD1d, thereby supporting the development of inv. NKT cells in mice. Therefore, we generated transgenic (Tg) mice expressing the human inv. V alpha 24-J alpha Q TCR chain in all T cells. The expression of the human inv. V alpha 24 TCR in TCR C alpha(-/-) mice indeed rescues the development of inv. NKT cells, which home preferentially to the liver and respond to the CD1d-restricted ligand alpha-galactosylceramide (alpha-GalCer). However, unlike inv. NKT cells from non-Tg mice, the majority of NKT cells in V alpha 24 Tg mice display a double-negative phenotype, as well as a significant increase in TCR V beta 7 and a corresponding decrease in TCR V beta 8.2 use. Despite the forced expression of the human CD1d-restricted TCR in C alpha(-/-) mice, staining with mCD1d-alpha-GalCer tetramers reveals that the absolute numbers of peripheral CD1d-dependent T lymphocytes increase at most by 2-fold. This increase is accounted for mainly by an increased fraction of NK1.1(-) T cells that bind CD1d-alpha-GalCer tetramers. These findings indicate that human inv. V alpha 24 TCR supports the development of CD1d-dependent lymphocytes in mice, and argue for a tight homeostatic control on the total number of inv. NKT cells. Thus, human inv. V alpha 24 TCR-expressing mice are a valuable model to study different aspects of the inv. NKT cell subset.

Role of NK1.1+ and AsGm-1+ cells in oral immunoregulation of experimental colitis

NK1.1 and AsGm-1 expressing cells play a role in immunomodulation. Our purpose was to determine the role of NK1.1+ and AsGm-1+ expressing cells in the inflammatory/tolerance paradigm in experimental colitis. Oral tolerance towards colitis-extracted proteins had previously been shown to alleviate experimental colitis. Colitis was induced in C57/B6 mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Oral tolerance was induced via five oral doses of proteins extracted from TNBS-colitis colonic wall. Clinical, macroscopic, and microscopic scores were used for colitis assessment. To evaluate the putative role of AsGm-1 in tolerance induction, depletion of AsGm-1 expressing cells was performed. To evaluate the mechanism of tolerance induction, liver-associated NKT lymphocytes were harvested 14 days following tolerance induction, and cultured with concanavalin A (con A) and colitis-extracted proteins. T cell subsets were measured by flow cytometry. Cytokine expression was measured by intracellular staining and enzyme-linked immunosorbent assay (ELISA). Orally tolerized mice exhibited significant alleviation of the clinical, macroscopic, and microscopic parameters of colitis, with increased CD4+ILA+/CD4+IFNgamma+ lymphocyte ratio, increased IL-4, and decreased IFNgamma and IL-12 serum levels. In contrast, orally fed mice that were AsGm-1 depleted showed evidence of severe colitis. These mice exhibited significant decreased CD4 +IL4+/CD4+IFNgamma+ ratios, and an increase in IFNgamma and IL-12, with decreased IL-4 levels. NKT cells harvested from tolerized mice secreted high levels of antiinflammatory cytokines. In contrast, in nontolerized mice, NKT cells mainly secreted proinflammatory cytokines. In a tolerized environment, both NK1.1 and AsGm-1 expressing cells are essential for disease alleviation. In contrast, in a nontolerized environment, AsGm-1 expressing cells support an antiinflammatory immune paradigm, while NKT lymphocytes support a proinflammatory shift.

U5A2-13, an antigen originally found on mouse NK-like T cells, is an early inducible cell surface antigen during lymphoid activation

We have previously reported a monoclonal antibody (mAb), U5A2-13 mAb, which originally recognizes a phenotypically and functionally similar population of natural killer (NK)-like T cells. In this study, we found that U5A2-13 antigen (U5A2-13) was expressed not only on NK-like T cells but also on T and B cells during activation. In contrast to the low levels of U5A2-13 on freshly harvested T and B cells, the activation of these cells by various stimuli resulted in high levels of expression of U5A2-13 in vitro and in vivo. Similar to CD69, U5A2-13 is also expressed in most mouse lymphoid cell lines but not in nonhematopoietic cells. U5A2-13 on T cells reached maximal expression by 24h after stimulation and returned to baseline levels after 3 days. However, U5A2-13 differed from CD69 since its expression profile was different on CD4(+)- and CD8(+)-activated T cells, phorbol ester-activated EL-4 cells, and activated splenocytes in CD69-deficient mice. In addition, immunoprecipitation study indicated that U5A2-13 is not identical to CD69. Importantly, the U5A2-13-positive population of CD4(+) T cells exhibited significant levels of cytokine producing activity upon stimulation. Overall, U5A2-13 is an early inducible cell surface antigen that could be involved in lymphocyte activation.

Immunomodulation of experimental colitis via caloric restriction: role of Nk1.1+ T cells

Inflammatory bowel diseases are immune-mediated disorders. Dietary restriction and NK1.1+ liver-associated lymphocytes (LAL) are considered to be involved in immunomodulation of autoimmune diseases. Our aim was to evaluate the effect of caloric restriction on experimental colitis and to determine NK1.1+ LAL function in immunoregulation. Experimental colitis was induced in C57 black mice by intracolonic instillation of trinitrobenzene sulfonic acid. Caloric restriction to 60% of the daily requirement was started 2 weeks prior to, or simultaneously with, colitis induction and continued throughout the study. Control mice were fed ad libitum. Colitis was assessed by standard clinical and macroscopic scores. To determine the mechanism involved in immunomodulation, liver lymphocytes were isolated and analyzed for NK1.1+ T-cell markers by FACS. T-cell function was evaluated by T-cell proliferation. Serum cytokines were measured by ELISA. Dietary restriction to 60% markedly ameliorated experimental colitis in both groups. These mice gained weight and showed improved macroscopic parameters of colitis. NK1.1+ LAL numbers increased fourfold and NKT cytotoxicity twofold in caloric-restricted mice. The antigen-specific T-cell proliferation index decreased (from 4.45 in controls to 1.15), and IFN-gamma and IL-12 serum levels decreased (from 290 to 200 pg and from 122 to 53 pg, respectively) in caloric-restricted mice. Our conclusion was that dietary restriction induced immunomodulation of experimental colitis and ameliorated the disease. This effect was mediated via an increase in NK1.1+ T lymphocytes, which may play a critical role in keeping the T-cell balance in immunoregulation.

Enhanced complement sensitivity of NK-T cells in murine thymus and spleen associated with presence of serum immunoglobulin

In vitro treatment of thymocytes and splenocytes with rabbit complement (C') alone induced significant reductions in the proportion of NK-T cells in murine system. The reduction appeared to be prominent in the thymic NK-T cells compared to that in splenic NK-T cells. No reductions were detected in other populations, such as T, B and NK cells. Thus, NK-T cells lineage-specifically showed the enhanced C' sensitivity. However, NK-T cells in T cell receptor (TCR) transgenic mice of RAG-/- background that lack B cells and antibodies exhibited no C' sensitivity. On the other hand those from the same TCR transgenic mice of RAG intact background that have a normal population of B cells and antibodies showed the C' sensitivity similar to that in normal mice. These findings suggest that the enhanced C' sensitivity observed in the NK-T cell population is associated with the NK-T specific autoantibodies. Indeed, we found that a subset of NK-T cells in the thymus bound mouse immunoglobulins. Similar observations were obtained with several strains of lupus model mice, some of which show a decrease of NK-T cells with aging. Possible roles of the enhanced C' sensitivity of NK-T cells in pathophysiological conditions in various mouse strains including lupus models are discussed.

Interleukin-10 modulation of alloreactivity and graft-versus-host reactions

BACKGROUND

The biological properties of interleukin (IL)-10 in tolerance induction and inhibition of alloreactivity have suggested a therapeutic use of this cytokine as an additional or alternative prophylaxis for graft-versus-host disease (GvHD). However, the effects of exogenous IL-10 on GvHD are mainly studied in animal models, and the results remain conflicting. This study aims to demonstrate, for the first time, whether the addition of exogenous IL-10 can reduce the severity of graft-versus-host reactions (GvHR) in humans.

METHODS

The regulatory role of exogenous IL-10 in GvHR was investigated using an in vitro human skin explant model. The effects of IL-10 on skin GvHR were tested in parallel with allo-antigen induced T-cell proliferation, cytolytic reactivity, and cytokine production.

RESULTS

In the presence of IL-10, the mixed lymphocyte reaction (MLR) primed responder cells showed significantly lower proliferative and cytolytic responses compared with the responder cells from the control MLR carried out in the absence of IL-10. The responder cells from IL-10 containing MLR induced significantly less severe skin GvHR and displayed a significantly reduced T-cell activation and cytokine production. A significant correlation was observed between the levels of TNF-alpha production and the sensitivity to IL-10 modulation of GvHR.

CONCLUSIONS

The addition of exogenous IL-10 strongly inhibited the broad alloreactivity initiated by primary MLR and significantly reduced the overall severity of skin GvHR induced by MLR primed responder cells. Responder cells producing high TNF-alpha following allogeneic stimulation appeared to be less sensitive to IL-10 modulation of GvHR.

NK 1.1+ T cell: a two-faced lymphocyte in immune modulation of the IL-4/IFN-gamma paradigm

T lymphocytes expressing NK1.1 marker (NK1.1+) have been suggested as being important in peripheral immune modulation. Alteration of the balance between Th1 proinflammatory and Th2 anti-inflammatory cytokine-producing cells can ameliorate immune-mediated disorders. The aim of the study was to determine the role of NK1.1+ lymphocytes in the pathogenesis of tolerance and proinflammatory states and to determine their role in altering the Th1/Th2 balance in experimental colitis. Colitis was induced in C57/B6 mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Mice received five oral doses of colonic proteins extracted from TNBS colitis colonic wall. Standard clinical, macroscopic, and microscopic scores were used for colitis assessment. Liver-associated lymphocytes and splenocytes were harvested 14 days following tolerance induction. Depletion of NK 1.1+ lymphocytes was performed 36 hr before lymphocyte harvesting. Lymphocytes were cultured for 12 hr with Con A and colitis extracted proteins. To evaluate the role of NK1.1+ lymphocytes in keeping a balance between immunogenic and tolerogenic subsets of cells, intracellular staining and flow cytometry assays were performed in tolerized and nontolerized mice. IL-4, IL-12, and IFN-gamma levels were measured by ELISA. Administration of mouse-derived colitis-extracted proteins ameliorated experimental colitis. Tolerized mice exhibited significant improvement in all macroscopic and microscopic parameters for colitis. Depletion of NK1.1 following tolerance induction significantly decreased the CD4(+)IL-4(+)/CD4(+)IFN-gamma(+) ratio in tolerized mice. However, depletion of NK1.1 lymphocytes in nontolerized mice increased the CD4(+)IL-4(+)/CD4(+)IFN-gamma(+) ratio, compared with nondepleted nontolerized mice. Induction of tolerance led to an increase in IL4 and a decrease in IFN-gamma levels. In the experimental colitis model NK1.1+ lymphocytes play a dual role: In the presence of peripheral tolerance they may be accountable for keeping the high CD4(+)IL-4(+)/CD4(+)IFN-gamma(+) ratio and disease alleviation. However, in nontolerized conditions they may induce a proinflammatory shift.

A composite picture of TcR alpha/beta(+) CD4(-)CD8(-) T Cells (alpha/beta-DNTCs) in humans with autoimmune lymphoproliferative syndrome

The discovery of an unusual T-cell subset characterized by the expression of the alpha/beta T-cell receptor without expression of either CD4 or CD8 [alpha/beta-double-negative T cells (alpha/beta-DNTCs)] provided critical insights in the evaluation of a "new" lymphoproliferative disorder known as autoimmune lymphoproliferative syndrome (ALPS). ALPS is a disorder of defective Fas-mediated lymphocyte apoptosis, manifested by accumulation of alpha/beta-DNTCs and other lymphocyte subsets, leading to lymphadenopathy and splenomegaly, autoimmunity, and an increased risk of lymphoma. The expanded population of alpha/beta-DNTCs from ALPS patients has a remarkable uniform phenotype that is for the most part similar to alpha/beta-DNTCs from mice with defective Fas (lpr) or Fas ligand (gld). This is in contrast to the minor alpha/beta-DNTC compartment in healthy individuals that contains multiple, immunophenotypically distinct subpopulations. Current data indicate that alpha/beta-DNTCs from ALPS patients are derived from cytotoxic CD8(+) T cells, chronically activated in vivo but anergic in vitro. Their anergic state may be related to persistent modifications of O-linked carbohydrates on cell surface molecules, such as CD43 and CD45, as well as to the increased presence of interleukin-10. Although largely consistent with a model of (linear) CD8(+) cytotoxic T-cell differentiation, the expression patterns of certain surface molecules, such as CD27 and CD28, are not consistent with this model. This may be the result of the perturbed homeostasis of lymphocytes in ALPS, thereby revealing pathways of differentiation and immunophenotypes, including phenotypes pertaining to cell surface glycosylation that are hidden from view in healthy individuals.

CD161+ T (NT) cells exist predominantly in human intestinal epithelium as well as in liver

It has been reported that human CD161 (NKR-P1A)+ T cells are counterparts of murine natural T (NT) cells and predominantly accumulate in the liver. However, NT cells in the human intestine have not been well analysed. The aim of this study was to assess the existence of NT cells in human intestinal epithelium and determine their phenotypical characterization. Intra-epithelial lymphocytes (IEL) were isolated from surgical specimens (jejunum, ileum and colon). The surface phenotype of IEL was analysed using a FACScan and compared with that of mononuclear cells (MNC) from other organs. CD161+ T cells were abundant in human intestinal epithelium as well as the liver. The majority of CD161+ T cells in IEL were CD8+ cells. About 50% of CD161+ T cells in hepatic lymphocytes (HL) expressed CD56, whereas only 14% of CD161+ T cells in IEL expressed CD56. The jejunum showed the greatest abundance of CD161+ T cells among the intestinal regions investigated. These results suggest that CD161+ T (NT) cells predominantly exist in human intestinal epithelium and may play an important role in local immunity.

Absence of the CD1 molecule up-regulates antitumor activity induced by CpG oligodeoxynucleotides in mice

The role of NKT cells on antitumor activity of CpG oligodeoxynucleotides (ODNs) was evaluated by peritumoral injections of CpG-ODNs in s.c. melanoma-bearing mice of strains differing in the number of NKT cells (athymic nude mice, recombination-activating gene(-/-)/transgenic V(alpha)14/Vbeta8.2 mice that generate NKT cells; J(alpha)281(-/-) mice and CD1(-/-) mice, which both have a strongly reduced number of NKT cells; and C57BL/6 wild-type mice). Tumor growth was significantly inhibited in strains enriched or depleted of NKT cells. The two murine strains having a reduced number of NKT cells differed significantly in the CpG-dependent tumor growth inhibition: in J(alpha)281(-/-) mice this inhibition was superimposable to that observed in C57BL/6 mice, while in CD1(-/-) mice the inhibition was dramatic. The increased tumor inhibition in CD1(-/-) correlated with a significantly higher ratio of IFN-gamma-IL-4 production in response to CpG as compared with C57BL/6 and J(alpha)281(-/-) mice. Experiments in which preparations of APCs and lymphocytes of the three strains were mixed showed that in the presence of APCs not expressing CD1, the production of CpG-ODN-induced type 1 cytokines was higher. Phenotype analysis of IFN-gamma- and IL-4-producing cells revealed that the differences between CD1(-/-) and C57BL/6 in the production of these two cytokines were mainly due to CD3(+) T lymphocytes. These data point to a regulatory role for the CD1 molecule in antitumor activity induced by danger signals, independently of V(alpha)14 NKT cells. The identification of a CD1-dependent suppressive subpopulation(s) might have important implications for the study of tolerance in the context of cancer, autoimmunity, and transplantation.

Liver injury due to sequential activation of natural killer cells and natural killer T cells by carrageenan

BACKGROUND/AIMS

Carrageenan is a high molecular weight polysaccharide and is widely used as a food additive for the solidification of plant oils and the thickening of many beverages. It is known that acute toxicity of carrageenan is possibly induced by the activation of phagocytic cells. We investigated other effects of carrageenan on lymphocytes in this study.

METHODS

Carrageenan was intraperitoneally injected once into mice and phenotypic and functional characterizations were conducted in various immune organs.

RESULTS

Natural killer (NK) cells were prominently activated in the liver, lungs, and spleen. A time-kinetic study showed sequential activation of NK and natural killer T (NKT) cells in the liver on days 3-10 after the injection. In parallel with the activation of NK and NKT cells in number, NK and NKT cytotoxicities were augmented. At this time, liver injury was induced, accompanied by massive hepatic necrosis and the elevation of transaminases. The in vivo elimination of NK cells reduced the liver injury induced by carrageenan. Direct binding of carrageenan onto NK cells was also demonstrated. Such a binding then induced a subsequent production of IFN gamma. Perforin molecules of NK cells were responsible for this liver injury.

CONCLUSIONS

These results suggest that not only phagocytic cells but also primitive lymphocyte (mainly NK cells) subsets might be important targets for the acute toxicity of carrageenan.

Presence of a novel subset of NKT cells bearing an invariant V(alpha)19.1-J(alpha)26 TCR alpha chain

CD1d-deficient (CD1d-/-) mouse lymphocytes were analyzed to classify the natural killer T (NKT) cells without reactivity to CD1d. The cells bearing a V(alpha)19.1-J(alpha)26 (AV19-AJ33) invariant TCR alpha chain, originally found in the peripheral blood lymphocytes, were demonstrated to be abundant in the NK1.1+ but not NK1.1- T cell population isolated from CD1d-/- mice. Moreover, more than half (11/21) of the hybrid cell lines established from CD1d-/- NKT cells expressed the V(alpha)19.1-J(alpha)26 invariant TCR alpha chain. The expression of the invariant V(alpha)19.1-J(alpha)26 mRNA was absent in beta2-microglobulin-deficient mice. Collectively, the present findings suggest the presence of a second NKT cell repertoire characterized by an invariant TCR alpha chain (V(alpha)19.1-J(alpha)26) that is selected by an MHC class I-like molecule other than CD1d.

NK T cells are a source of early interleukin-4 following infection with third-stage larvae of the filarial nematode Brugia pahangi

Infection of C57BL/6 mice with the third-stage larvae of Brugia pahangi results in a rapid expansion of NK1.1(+) T cells in the spleen and draining lymph nodes. NK T cells produced interleukin-4 in the spleen within 24 h of infection, and these cells were CD4(-).

Cutting edge: analysis of human V alpha 24+CD8+ NK T cells activated by alpha-galactosylceramide-pulsed monocyte-derived dendritic cells

Human Valpha24(+) NKT cells constitute a counterpart of mouse Valpha14(+) NKT cells, both of which use an invariant TCR-alpha chain. The human Valpha24(+) NKT cells as well as mouse Valpha14(+) NKT cells are activated by glycolipids in a CD1d-restricted manner and produce many immunomodulatory cytokines, possibly affecting the immune balance. In mice, it has been considered from extensive investigations that Valpha14(+)CD8(+) NKT cells that express invariant TCR do not exist. Here we introduce human Valpha24(+)CD8(+) NKT cells. These cells share important features of Valpha24(+) NKT cells in common, but in contrast to CD4(-)CD8(-) (double-negative) or CD4(+) Valpha24(+) NKT cells, they do not produce IL-4. Our discovery may extend and deepen the research field of Valpha24(+) NKT cells as well as help to understand the mechanism of the immune balance-related diseases.

Association of CD8+ natural killer T cells in the liver with neonatal tolerance phenomenon

BACKGROUND

Neonatal tolerance is a very interesting phenomenon, because even allogeneic skin grafts are not rejected in these mice at the adult stage. However, the underlying mechanism remains unclear.

METHODS

In this study we prepared such tolerant C57BL/6 (B6) mice (H-2b) by the injection of allogeneic lymphocytes of BALB/c origin (H-2d) at the neonatal stage.

RESULTS

The total number of liver lymphocytes in these tolerant mice was found to increase when it was examined at the adult stage. Nevertheless, the retention of allogeneic lymphocytes that were injected at the neonatal stage was highest in the spleen. It is speculated that these allogeneic lymphocytes stimulate the hepatic immune system via the portal vein and that such stimulation maintains the tolerance phenomenon. Indeed, these tolerant mice showed elevated levels of IL-2R beta+ CD3int cells (i.e., extrathymic T cells) and NK1.1+ CD3int cells (i.e., NKT cells) in the liver. Even more interestingly, the number and proportion of CD8+ NKT cells, which are usually a minor population in normal mice, increased among NKT cells in the liver of tolerant mice. This became much more prominent when tolerant mice were grafted with allogeneic (H-2d) skin.

CONCLUSION

In conjunction with additional data from a cell-transfer experiment and a splenectomy experiment, our results suggest that CD8+ NKT cells in the liver of tolerant mice might be intimately associated with the neonatal tolerance phenomenon.

Sequential production of interferon-gamma by NK1.1(+) T cells and natural killer cells is essential for the antimetastatic effect of alpha-galactosylceramide

The antimetastatic effect of the CD1d-binding glycolipid, alpha-galactosylceramide (alpha-GalCer), is mediated by NK1.1(+)T (NKT) cells; however, the mechanisms behind this process are poorly defined. Although it has been shown to involve NK cells and interferon-gamma (IFN-gamma) production, the way these factors collaborate to mediate effective tumor rejection and the importance of other factors characteristic of NKT cell and NK cell activation are unknown. Using gene-targeted mice and antibody treatments, the critical need for interleukin 12 (IL-12), IFN-gamma, and NK cells has been shown in the antimetastatic activity of alpha-GalCer in the lungs and the liver. By contrast, in lung and liver metastasis models, cytotoxic molecules expressed by NK cells and NKT cells (perforin, Fas ligand, and tumor necrosis factor-related apoptosis-inducing ligand) and an NKT cell-secreted cytokine, IL-4, were not necessary for the antitumor activity of alpha-GalCer. Like IL-12, IL-18 was required for optimal serum IFN-gamma induction and control of lung metastases by alpha-GalCer. IL-18 was unnecessary for alpha-GalCer-related suppression of liver metastases. Most importantly, after adoptive transfer of alpha-GalCer-reactive NKT cells or NK cells into NKT cell-deficient, IFN-gamma-deficient, or RAG-1-deficient mice, it was demonstrated that the sequential production of IFN-gamma by NKT cells and NK cells was absolutely required to reconstitute the antimetastatic activity of alpha-GalCer.

NKT cells-containing inflammatory lesions induced by Yersinia pseudotuberculosis glycolipids

Valpha14-expressing NKT (invNKT) cells are a population of non-conventional T lymphocytes (TL) that bridge mammalian innate and adaptive immunity. Their role in infectious diseases and inflammatory processes is still largely ununderstood. A previous report has shown that an acute granulomatous-like reaction can be elicited by sub-cutaneous injection of Mycobacterium tuberculosis glycolipids in mice, and that recruitment of invNKT cells at the injection site is instrumental in this process. Here, we describe the mouse response to enterobacterium Yersinia pseudotuberculosis glycolipids extracts during the first week post injection. The cellular reaction is an acute inflammatory infiltrate where TL are abundant from early times on. InvNKT cells are present in the lesions, detectable as early as day 1 post injection. They compose all of the Valpha14-expressing TL, although conventional T cells expressing non-Valpha14 alpha-chains can be detected. The reaction is strictly dependent on ester-linked fatty acids as mild alkaline treatment of the extract prior to injection results in the absence of analysable lesions. Thus, glycolipids from Yersinia induce inflammatory lesions comparable to those induced by mycobacteria glycolipids, in spite of the totally different cell wall composition in the two genera. Moreover, the present findings show that invNKT cell response is not unique to mycobacterial glycolipids.

Role of primary intrahepatic T-cell activation in the 'liver tolerance effect'

There is accumulating evidence suggesting that hepatic permeability to both naive and activated T lymphocytes may be unique among the solid organs. The possibility that the liver may act as a site of primary activation for CD8+ T lymphocytes is supported by experimental data and may contribute to some of the unique immunological properties of this organ, particularly its ability to induce antigen-specific tolerance. This review discusses the nature of the liver APC inducing primary T-cell activation within the liver: Kupffer cells, liver dendritic cells, liver sinusoidal endothelial cells and hepatocytes are favourably located to allow physical contact with circulating T lymphocytes. Here, we examine the capability of each cell type to act as APC for naive CD4+ or CD8+ T cells and to induce tolerance.

Enforced expression of the Ikaros isoform IK5 decreases the numbers of extrathymic intraepithelial lymphocytes and natural killer 1.1+ T cells

The zinc-finger protein Ikaros plays an important role in lymphoid homeostasis, and loss of Ikaros expression through germline disruption impairs lymphoid development. However, the role played by Ikaros after commitment to the T-cell lineage is unclear. To address this question, this study used the lck proximal promoter to drive the expression in T-cell progenitors of a naturally occurring short Ikaros isoform (IK5), which lacks the DNA-binding domain, reasoning that IK5 will form heterodimers with long isoforms and perturb their function. The IK5 transgene led to a selective and dramatic decrease in extrathymic intestinal intraepithelial lymphocytes (IELs) and natural killer 1.1+ T (NK T) cells with little effect on conventional alphabeta T cells, which resembles the T-cell phenotype of interleukin-15 receptor alpha chain (IL-15Ralpha) and IL-2/IL-15 receptor beta chain (IL-2Rbeta) knockout mice. The expression of IL-2Rbeta on double-negative T-cell progenitors of bi-5 was reduced, but enforced expression of IL-2Rbeta did not rescue IELs or NK T cells in bi-5 transgenic mice, suggesting that Ikaros or Ikaros family members regulate the expression of additional genes that are essential for the development of IELs and NK T cells. The study concludes that modest changes in the ratio of short to long Ikaros isoforms can substantially perturb T-cell development, and the development of IELs and NK T cells is particularly sensitive to such changes.

Aggressive Epstein-Barr virus-associated, CD8+, CD30+, CD56+, surface CD3-, natural killer (NK)-like cytotoxic T-cell lymphoma

We report an unusual case of aggressive natural killer (NK)-like cytotoxic T-cell lymphoma in a previously healthy immunocompetent West African male. He presented with a fever of unknown origin, subsequently developed erythematous skin nodules, generalized lymphadenopathy, and hepatosplenomegaly, and then died of multiple organ failure. A skin nodule and lymph node biopsy showed an infiltrate of pleomorphic atypical medium and large lymphoid cells with extensive necrosis and prominent apoptosis. Peripheral blood and ascites also harbored these cells, with cytology revealing irregular nuclear folding and basophilic cytoplasm, and some with azurophilic cytoplasmic granules. Flow cytometry and immunohistochemistry demonstrated the expression of CD2, CD7, CD8, CD30, CD56, and cytoplasmic but not surface CD3. In situ hybridization demonstrated Epstein-Barr virus transcripts. A monoclonal T-cell receptor gamma chain gene rearrangement was detected by polymerase chain reaction. This is the first reported case of an NK-like T-cell lymphoma with these unusual features, making precise classification difficult. Some features suggest an NK1.1 or NKT lymphocyte origin. Because the earliest clinical manifestation was splenomegaly and abnormal liver function, the normal cellular counterpart may be a distinct subset of NK1.1 cells normally present in hepatosplenic sinusoids. This tumor disseminated early and pursued a fulminant clinical course, thus emphasizing the importance of early recognition and diagnosis.

NKT cells and type-1 diabetes and the "hygiene hypothesis" to explain the rising incidence rates

Immune-mediated (type-1) diabetes (IMD) is a multigenetic disease that is strongly influenced by the environment. Whereas the incidence rates are steadily rising worldwide, less than half of affected identical twins ever become concordant for IMD or even beta-cell autoimmunity. Worldwide, it is the tropical regions of the world that are replete in infectious and parasitic diseases that are the least affected. Repeated efforts to identify the putative inductive agents for beta-cell autoimmunity have proved unrewarding. Rather, we suggest that some environments are less protective than others and argue that it is the fall in incidences of infectious diseases and intestinal parasites that are likely responsible for the rise in autoimmune diseases like IMD in the West. Nonobese diabetic (NOD) mice reared in gnotobiotic environments have only worsened diabetes, while recent studies suggest that multiple defects in immune tolerance to self must be present before IMD can develop in the human or mouse. We speculate herein that the deficiency in natural killer T (NKT) cells in IMD in both species may be both genetic and environmentally influenced, predisposing to pancreatic beta-cell autoimmunity through a dysfunction of immunoregulatory T cells, with defective peripheral control of islet cell protein autoreactive cytotoxic CD8+ T cells. The encouraging results in NOD mice using alpha-galactosylceramide to stimulate NKT cells now warrant trials with this and other glycolipid NKT cell-stimulating agents in humans. Since it has become apparent that autoimmune diseases such as IMD are the result of an underlying immunodeficiency state, we strongly argue that its effective prevention will likely come through the use of immunostimulation and not through side effect-prone immunosuppression.

Abundance of unconventional CD8(+) natural killer T cells in the large intestine

Natural killer T (NKT) cells are mainly present in the liver and thymus, and the majority of these T cells express either a CD4(+) or a double-negative (DN) CD4(-)8(-) phenotype. In the present study, we examined whether such NKT cells were present in the intestine. NKT cells were rare in all sites of the small intestine, including an intraepithelial site. However, a considerable number of NKT cells were found at an intraepithelial site in the large intestine. This result was confirmed by both immunofluorescence and immunohistochemistry. In contrast to conventional NKT cells, NKT cells in the large intestine were CD8(+) or DN CD4(-)8(-). In the case of conventional NKT cells, their existence is known to depend on non-classical MHC class I-like antigens (i. e. CD1d) but not on classical MHC class I antigens. However, the NKT cells in the large intestine were independent of the presence of both CD1d and classical MHC class I antigens. These results were obtained using knockout mice lacking the corresponding genes and molecules. NKT cells in the large intestine were mainly alpha betaTCR(+) (> 75 %) but did not use an invariant chain of Valpha14Jalpha281, which is preferentially used by conventional NKT cells. These NKT cells did not bias the TCR-Vbeta usage toward Vbeta8. These findings suggest that the large intestine is a site in which unconventional NKT cells carrying the CD8(+) phenotype (or DN CD4(-)8(-)) are abundant and that these cells are independent of MHC and MHC-like antigens.

Immunomodulation of experimental colitis: the role of NK1.1 liver lymphocytes and surrogate antigens--bystander effect

The imbalance between Th1 pro-inflammatory and Th2 anti-inflammatory cytokine-producing cells plays a major role in the pathogenesis of inflammatory bowel disease (IBD). Induction of oral tolerance to colitis-extracted proteins was previously shown to down-regulate the anti-colon immune response, thereby alleviating experimental colitis. Immune bystander effect and liver-associated lymphocytes expressing the NK1.1 marker (NK1.1(+) LAL) have been suggested as being important in tolerance induction. The aims of the present study were to determine whether oral administration of inflammatory and non-inflammatory colon-extracted proteins of different species can induce peripheral immune tolerance and alleviate experimental colitis; and to examine the role of NK1.1(+) LAL in oral tolerance induction. Colitis was induced in C57/B6 mice by intracolonic instillation of trinitrobenzene sulphonic acid (TNBS). Mice received six oral doses of colonic proteins extracted from TNBS-colitis colonic wall, or normal colonic wall, from four different species. Standard clinical, macroscopic, and microscopic scores were used for colitis assessment. Serum interferon gamma (IFNgamma) and interleukin 10 (IL10) levels were measured by ELISA. To evaluate the role of NK1.1(+) LAL in maintaining the balance between immunogenic and tolerogenic subsets of cells, their cytotoxicity functions were tested in tolerized and non-tolerized-mice. The administration of mouse-derived colitis-extracted proteins, or of surrogate proteins extracted from normal mouse colon, or from rat or human inflammatory colons, was found to alleviate experimental colitis. Tolerized mice had less diarrhoea; showed a marked reduction of colonic ulceration, intestinal and peritoneal adhesions, wall thickness, and oedema; and demonstrated a significant improvement of all microscopic parameters for colitis. Induction of tolerance led to an increase in IL10 and a decrease in IFNgamma serum levels. NK1.1(+) LAL cytotoxicity function increased markedly in tolerized mice. In contrast, mice fed with proteins extracted from normal rat, rabbit, and human colon, or from rabbit inflammatory colon, developed severe colitis, with a marked increase in IFNgamma and a decrease in IL10 serum levels, and down-regulation of NK1.1(+) LAL function. This study has shown that oral tolerance can be induced in experimental colitis by means of the feeding of surrogate antigens; this alleviates experimental colitis. NK1.1(+) LAL cytotoxicity function is associated with peripheral tolerance induction and may help to maintain the Th1/Th2 immune balance.

Glycolipid targets of CD1-mediated T-cell responses

Members of the CD1 family of antigen-presenting molecules bind and present a variety of mammalian and microbial glycolipids for specific recognition by T cells. CD1 proteins accomplish their antigen-presenting function by binding the alkyl chains of the antigens within a deep, hydrophobic groove on the membrane distal surface of CD1, making the hydrophilic elements of the antigen available for contact with the variable regions of antigen-specific T-cell receptors. Most models of CD1-restricted T cells function in infectious, neoplastic, or autoimmune diseases and are based on the premise that CD1-restricted T-cell responses are initiated by alterations in cellular glycolipid content. Although a growing number of self, altered self and foreign glycolipid antigens have been identified, the cellular mechanisms that could lead to the generation of antigenic glycolipids within cells, or control the presentation of particular classes of altered self or microbial glycolipids in disease states have only recently come under investigation. Here we review the structures of known glycolipid antigens for T cells and discuss how the chemical nature of these antigens, which is quite different from that of peptides, influences their recognition by T cells.

Natural killer T cells reactive to a single glycolipid exhibit a highly diverse T cell receptor beta repertoire and small clone size

CD1d-restricted natural killer (NK) T cells reactive with the glycolipid alpha-galactosylceramide (alpha-GalCer) are a distinct lymphocyte sublineage. They express an invariant Valpha14-Jalpha18 T cell receptor (TcR), but the role of the beta chain has been controversial. Here, we have used CD1d tetramers to identify and isolate NK T cells based on their antigen specificity. In mice lacking germline Vbeta8, most of the alpha-GalCer-reactive T cells express either Vbeta2 or Vbeta7, strong Vbeta selection being revealed by the lack of an increase in other Vbeta regions. By contrast to the selection for complementarity determining region (CDR) 3beta sequences in some anti-peptide responses, alpha-GalCer-reactive T cells have polyclonal CDR3beta sequences. There is little CDR3beta sequence redundancy between organs or individual mice, and, surprisingly, there also is no evidence for organ-specific CDR3beta sequence motifs. These data argue against a T cell receptor-mediated self-reactivity for tissue-specific CD1d-bound ligands. Each NKT clone is represented by only 5-10 cells. This clone size is similar to naive conventional T cells, and much lower than that reported for memory T cells, although NK T cells have an activated/memory phenotype.

Regulation of NKT cells by Ly49: analysis of primary NKT cells and generation of NKT cell line

TCRalphabeta(+)NK1.1(+) (NKT) cells are known to express various NK cell-associated molecules including the Ly49 family of receptors for MHC class I, but its functional significance has been unclear. Here, we examined the expression of Ly49A, C/I and G2 on various NKT cell populations from normal and MHC class I-deficient C57BL/6 mice as well as their responsiveness to alpha-galactosylceramide (alpha-GalCer), a potent stimulator of CD1d-restricted NKT cells. The frequency and the level of Ly49 expression varied among NKT cells from different tissues, and were regulated by the expression of MHC class I and CD1d in the host. Stimulation of various NKT cells with alpha-GalCer suggested that Ly49 expression inversely correlates with the responsiveness of NKT cells to alpha-GalCer. Moreover, alpha-GalCer presented by normal dendritic cells stimulated purified Ly49(-), but not Ly49(+), splenic NKT cells, whereas MHC class I-deficient dendritic cells presented alpha-GalCer to both Ly49(+) and Ly49(-) NKT cells equally well. Therefore, MHC class I on APCs seems to inhibit activation of NKT cells expressing Ly49. To further characterize CD1d-restricted NKT cells, we generated an alpha-GalCer-responsive NKT cell line from thymocytes. The line could only be generated from Ly49(-)NK1.1(+)CD4(+) thymocytes but not from other NKT cell subsets, and it lost expression of NK1.1 and CD4 during culture. Together, these results indicate the functional significance of Ly49 expression on NKT cells.