Depletion Of NKT Cells Research Articles

Conditional NKT Cell Depletion in Mice Reveals a Negative Feedback Loop That Regulates CTL Cross-Priming.

NKT cells are unconventional T cells whose biological role is incompletely understood. Similar to TH cells, activated NKT cells can cause dendritic cell (DC) maturation, which is required for effective CTL responses. However, it is unclear whether and how NKT cells affect CTLs downstream of the DC maturation phase. This is partially due to the lack of techniques to conditionally deplete NKT cells invivo. To overcome this problem, we have developed two approaches for this purpose in mice: the first is based on mixed bone marrow chimeras where Jα18 knockout and depletable CD90 congenic bone marrow is combined, and the second used PLZFCre × iDTR bone marrow chimeras, which target innate-like T cells. Using these tools, we found that NKT cell depletion at 20 h, that is, after initial DC activation, did not render CTLs helpless, as CD40L signaling by non-NKT cells sufficed. Instead, NKT cell depletion even augmented CD8 T cell expansion and cytotoxicity by mechanisms distinct from reduced STAT6 signaling. These findings revealed a negative feedback loop by which NKT cells control CTL cross-priming downstream of DC maturation. The techniques described in this study expand the toolbox to study NKT cells and other unconventional T cell subsets invivo and uncovered a hidden immunoregulatory mechanism.

Abstract 2096: Natural killer cells inhibit CD4+ T cell mediated IL-9 production in head and neck Cancer

Abstract Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer in the world, yet 5 year survival remains poor for those with recurrence despite advances in treatment such as immunotherapy. Checkpoint blockade substantially improved survival in ~20% of recurrent and/or metastatic HNSCC patients. However, given the lack of efficacy in most patients, and the known immunosuppressive nature of HNSCC, exploring other potential immune cell therapeutic targets is of interest. Decreased natural killer (NK) as well as increased immunosuppressive CD4+ regulatory T cells (Tregs) in both peripheral blood and the tumor microenvironment are associated with a poor prognosis in HNSCC. We discovered that the anti-diabetes drug, metformin, which is also known to improve immune cell function, not only increases peripheral NK cells in HNSCC patients to the level of healthy controls, but also suppresses IL-9 secretion from NK cells. IL-9 has been implicated as a driving factor in allergic disease, a poor prognosis factor in hematologic malignancies, and an enhancer of T-reg immunosuppressive abilities. However, the function of IL-9 in solid tumors is poorly understood. Interestingly, upon depletion of CD56+ NK and NKT cells from peripheral blood mononuclear cells (PBMCs), there was a significant increase of IL-9 secretion. This effect was negated upon depletion of CD4+ T cells suggesting that NK cells may directly or indirectly inhibit CD4+ T cell IL-9 production. In order to understand potential consequences of IL-9 overproduction, we subjected HNSCC cell lines, which we demonstrated express IL9 receptor, to exogenous IL-9 which resulted in enhanced proliferation. We also found that IL-9 plasma levels are high in HNSCC patients compared to healthy controls corroborating a potential tumorigenic role for IL-9. In order to elucidate potential mechanism(s) by which NK/NKT cells regulate CD4+ T cell production, we performed single-cell RNAseq on PBMCs upon NK and NKT cell depletion. We also performed flow cytometry to identify specific CD4+ cell types responsible for increased IL-9 production and the consequential changes in other immune cell phenotypes upon the absence of NK/NKT cells. Understanding the role of IL-9 in HNSCC will be important for utilizing IL-9 as a potential marker for HNSCC prognosis as well as a possible target for future immunotherapy approaches. Citation Format: McKenzie Crist, Maria Lehn, Vinita Takiar, Trisha Wise-Draper. Natural killer cells inhibit CD4+ T cell mediated IL-9 production in head and neck Cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2096.

Conventional NK Cells and Type 1 Innate Lymphoid Cells Do Not Influence Pathogenesis of Experimental Glomerulonephritis.

Innate lymphoid cells (ILCs) that express NK cell receptors (NCRs) and the transcription factor T-bet populate nonlymphoid tissues and are crucial in immune responses against viral infections and malignancies. Recent studies highlighted the heterogeneity of this ILC population and extended their functional spectrum to include important roles in tissue homeostasis and autoimmunity. In this article, we provide detailed profiling of NCR+T-bet+ ILC populations in the murine kidney, identifying conventional NK (cNK) cells and type 1 ILCs (ILC1s) as the two major subsets. Induction of renal inflammation in a mouse model of glomerulonephritis did not substantially influence abundance or phenotype of cNK cells or ILC1s in the kidney. For functional analyses in this model, widely used depletion strategies for total NCR+ ILCs (anti-NK1.1 Ab application) and cNK cells (anti-asialoGM1 serum application) were unreliable tools, because they were accompanied by significant off-target depletion of kidney NKT cells and CD8+ T cells, respectively. However, neither depletion of cNK cells and ILC1s in NKT cell-deficient mice nor specific genetic deletion of cNK cells in Ncr1 Cre/wt × Eomes fl/fl mice altered the clinical course of experimental glomerulonephritis. In summary, we show in this article that cNK cells and ILC1s are dispensable for initiation and progression of immune-mediated glomerular disease and advise caution in the use of standard Ab depletion methods to study NCR+ ILC function in mouse models.

Systemic alterations in leukocyte subsets and the protective role of NKT cells in the mouse model of diabetic retinopathy

The involvement of leukocytes in the pathophysiology of DR has mostly examined the role of monocytes and neutrophils with little emphasis on other immune cell types. In this study, we determined the systemic alterations in T cell subsets, myeloid cell types, NK cells, and NKT cells in the streptozotocin (STZ) mouse model of diabetic retinopathy (DR), and the role of NKT cells on retinal leukostasis and permeability changes. C57BL/6 J mice were made diabetic with 60 mg/kg dose of STZ given for 5-days. Flow cytometry assay measured the frequency of leukocyte subsets in the peripheral blood, spleen, and bone marrow of STZ- and vehicle-treated C57BL/6 J mice. Our results showed an increased proportion of memory CD8 T cells and interferon-gamma (IFN-γ) secreting CD8 T cells in the bone marrow of STZ-treated compared to control mice. Subsequently, increased production of inflammatory monocytes in the bone marrow and an enhanced frequency of CD11b + cells in the diabetic retina were seen in STZ-treated compared to control mice. The diabetic mice also exhibited a decrease in total NKT and CD4+NKT cells. A monoclonal antibody-based approach depleted NKT cells from STZ-treated mice, followed by measurements of retinal vascular permeability and leukostasis. The depletion of NKT cells in STZ-treated mice resulted in a significant increase in vascular permeability in the retinal tissue. Together, our results strongly imply the involvement of NKT cells in regulating the pathophysiology of the diabetic retina.

Abstract 1480: A novel mechanism of immunosuppression via nanotube mediated mitochondrial trafficking between cancer cell and immune cell

Abstract Cancer cells deploy multiple mechanisms for immune evasion. Here we report a novel mechanism of cancer cell-induced immune evasion via organelle trafficking between cancer cells and immune cells through physical nanotubes. Using high resolution scanning electron microscopy to analyze a co-culture assay of breast cancer cells and NKT cells revealed that the cancer cells and NKT cells form physical nanotube connections at early time points. Immunofluorescence imaging and quantification using flow cytometry revealed that the cancer cells rapidly hijack mitochondria from immune cells through these nanotubes. The transfer of mitochondria from immune cell to cancer cells imposes a metabolic impairment and results in a reduced population of immune cells. This is not observed in a control coculture using a Boyden chamber, where the two cell types are prevented from forming nanotubes. As the nanotubes are assembled via cytoskeletal rearrangement, we next tested whether the members of Rho-family of GTPases, Cdc42, Ral and Rac are involved in the actin polymerization. Indeed, an inhibitor for Cdc42/Rac1 GTPase inhibitor (ML141) and a geranylgeranyltransferase 1 inhibitor (L-778,123) significantly decreased mitochondrial transfer, and prevented the depletion of NKT cells in co-culture. Furthermore, treating 4T1 tumor-bearing animals with a combination of L-778,123 and a PD1 immune checkpoint inhibitor increased the anti-tumor efficacy compared to PD1 inhibition alone. Conclusion: Our study sheds insights on a novel mechanism of cancer immune suppression via nanotube-mediated intercellular organelle trafficking. The efficacy of GTPase- or geranylgeranyltransferase-inhibitors, in perturbing this process, and the increased efficacy of the combination with PD1 inhibitor, opens up the possibility of developing these as novel immunotherapy agents for cancer. Citation Format: Tanmoy Saha, Chinmayee Dash, Sachin Khiste, Shiladitya Sengupta. A novel mechanism of immunosuppression via nanotube mediated mitochondrial trafficking between cancer cell and immune cell [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1480.

P-A6 A Possible Role for Retinoic Acid in the Functional cure of SIV Infections in ART/α4β7 mAb-treated Monkeys

Our team of collaborators has recently reported that combining short term antiretroviral therapy (ART) with the in vivo administration of a primatized monoclonal antibody against the α4β7 integrin (α4β7 mAb) in SIV-infected macaques resulted in sustained control of viremia without need for continued therapy. We have determined that acute SIV infection caused a rapid and sustained drop in plasma retinoic acid (RA) levels that was not corrected upon ART-mediated control of viral replication, but was restored soon after start of α4β7 mAb treatment. This was followed by the rebound of certain CD8α+ NK lymphocytes, cells known to be regulated by RA. Depletion studies of the α4β7 mAb-treated “SIV controllers” with anti-CD8α and anti-CD8β Abs have indicated that rebound of viremia and return to suppression tracks most closely with the depletion and reappearance of NK and NKT cells. In parallel in vitro studies using a cell line model of latent SIV infection (Hut78 and SIV-Hut78), we determined that SIV infection inhibited RA production, while α4β7 mAb treatment can stimulate RA production. The data indicated that SIV-Hut78 cells showed a marked reduction in RALDH2 expression (the key regulatory enzyme in RA biosynthesis). The retinol chaperone protein RBP1 was also reduced in SIV-Hut78 cells. Together, these in vivo and in vitro studies indicate that an increase in RA levels is an early sign of the efficacy of α4β7 mAb treatment and suggests that ligation of the α4β7 integrin leads to intra-cellular signaling events that include the restoration of RA production by select RALDH-expressing cells, and signals that induce NK cell activation/re-distribution that may in concert play a fundamental role in sustained control of viremia.

Macrophage migration inhibitory factor triggers chemotaxis of CD74+CXCR2+ NKT cells in chemically induced IFN-γ-mediated skin inflammation.

IFN-γ mediates chemically induced skin inflammation; however, the mechanism by which IFN-γ-producing cells are recruited to the sites of inflammation remains undefined. Secretion of macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, from damaged cells may promote immune cell recruitment. We hypothesized that MIF triggers an initial step in the chemotaxis of IFN-γ-producing cells in chemically induced skin inflammation. Using acute and chronic models of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation in mouse ears, MIF expression was examined, and its role in this process was investigated pharmacologically. The cell populations targeted by MIF, their receptor expression patterns, and the effects of MIF on cell migration were examined. TPA directly caused cytotoxicity accompanied by MIF release in mouse ear epidermal keratinocytes, as well as in human keratinocytic HaCaT cells. Treatment with the MIF antagonist (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester considerably attenuated TPA-induced ear swelling, leukocyte infiltration, epidermal cell proliferation, and dermal angiogenesis. Inhibition of MIF greatly diminished the dermal infiltration of IFN-γ(+) NKT cells, whereas the addition of exogenous TPA and MIF to NKT cells promoted their IFN-γ production and migration, respectively. MIF specifically triggered the chemotaxis of NKT cells via CD74 and CXCR2, and the resulting depletion of NKT cells abolished TPA-induced skin inflammation. In TPA-induced skin inflammation, MIF is released from damaged keratinocytes and then triggers the chemotaxis of CD74(+)CXCR2(+) NKT cells for IFN-γ production.

Systemic lymphopenia results in loss of suppressive lymphocytes from precancerous skin (P2081)

Abstract We have previously demonstrated an immunosuppressive role for NKT cells that infiltrate hyperplastic skin epithelium in transgenic mice expressing HPV16E7 oncoprotein under a keratin 14 promoter (K14E7 mice)(Mattarollo et al.(2010) J. Immunol. 184:1242-1250). However, depletion of NKT cells is not easily achieved in either mouse or human. We hypothesized that systemic depletion of lymphocytes might result in turnover of NKT cells (and other lymphocytes) within the precancerous skin without replacement from the circulation. Without these locally suppressive populations, the precancer might then be more susceptible to a transferred immune system. When K14E7 skin was grafted onto RAG1-/- mice, which lack lymphocytes, the grafted skin became depleted of T cells (including NKT cells) within 7 days and remained depleted. Depletion of skin lymphocytes could also be achieved using cyclophosphamide and fludarabine, although with less efficiency. Preliminary data suggests that K14E7 skin grafts on RAG1-/- mice become susceptible to graft rejection after transfer of a new immune system. Together the data suggest that systemic lymphodepletion results in a loss of local, suppressive lymphocytes at the precancerous site and that this might enhance the immune mediated clearance of skin precancers.

Tim-3/Galectin-9 Regulate the Homeostasis of Hepatic NKT Cells in a Murine Model of Nonalcoholic Fatty Liver Disease

T cell Ig and mucin domain (Tim)-3 is well known to interact with its natural ligand, Galectin-9 (Gal-9), to regulate T cell function. However, little is known about the function of Tim-3/Gal-9 signaling in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) mediated by hepatic NKT cells that also express Tim-3. In the current study, we define the role and the mechanism of Tim-3/Gal-9 signaling in hepatic NKT cell regulation in a mouse model of diet-induced NAFLD. Adult male wild-type or CD1d knockout C57BL/6 mice were fed a high-fat diet to induce steatosis. Some of the mice also received one or a combination of Gal-9, anti-IL-15R/IL-15 mAb, rIL-15, α-galactosylceramide, and multilamellar liposomes containing Cl(2)MDP. The expression of Tim-3 and various markers reflecting cell proliferation, activation, cytokine production, and apoptosis was analyzed. Liver histology, steatosis grade, and hepatic triglyceride content were also evaluated. In the liver, Tim-3(+) NKT cells are in an activated state, and Gal-9 directly induces Tim-3(+) NKT cell apoptosis and contributes to the depletion of NKT cells in diet-induced steatosis. However, Gal-9 also interacts with Tim-3-expressing Kupffer cells to induce secretion of IL-15, thus promoting NKT cell proliferation. Exogenous administration of Gal-9 significantly ameliorates diet-induced steatosis by modulating hepatic NKT cell function. In summary, the Tim-3/Gal-9-signaling pathway plays a critical role in the homeostasis of hepatic NKT cells through activation-induced apoptosis and secondary proliferation and, thus, contributes to the pathogenesis of NAFLD.

Interruption of CXCL13-CXCR5 axis increases upper genital tract pathology and activation of NKT cells following chlamydial genital infection.

BackgroundRegulation of immune responses is critical for controlling inflammation and disruption of this process can lead to tissue damage. We reported that CXCL13 was induced in fallopian tube tissue following C. trachomatis infection. Here, we examined the influence of the CXCL13-CXCR5 axis in chlamydial genital infection.Methodology and Principal FindingsDisruption of the CXCL13-CXCR5 axis by injecting anti-CXCL13 Ab to BALB/c mice or using Cxcr5−/− mice increased chronic inflammation in the upper genital tract (UGT; uterine horns and oviducts) after Chlamydia muridarum genital infection (GT). Further studies in Cxcr5−/− mice showed an elevation in bacterial burden in the GT and increased numbers of neutrophils, activated DCs and activated NKT cells early after infection. After resolution, we noted increased fibrosis and the accumulation of a variety of T cells subsets (CD4-IFNγ, CD4-IL-17, CD4-IL-10 & CD8-TNFα) in the oviducts. NKT cell depletion in vitro reduced IL-17α and various cytokines and chemokines, suggesting that activated NKT cells modulate neutrophils and DCs through cytokine/chemokine secretion. Further, chlamydial glycolipids directly activated two distinct types of NKT cell hybridomas in a cell-free CD1d presentation assay and genital infection of Cd1d−/− mice showed reduced oviduct inflammation compared to WT mice. CXCR5 involvement in pathology was also noted using single-nucleotide polymorphism analysis in C. trachomatis infected women attending a sub-fertility clinic. Women who developed tubal pathology after a C. trachomatis infection had a decrease in the frequency of CXCR5 SNP +10950 T>C (rs3922).Conclusions/SignificanceThese experiments indicate that disruption of the CXCL13-CXCR5 axis permits increased activation of NKT cells by type I and type II glycolipids of Chlamydia muridarum and results in UGT pathology potentially through increased numbers of neutrophils and T cell subsets associated with UGT pathology. In addition, CXCR5 appears to contribute to inter-individual differences in human tubal pathology following C. trachomatis infection.

Innate immune responses involving natural killer and natural killer T cells promote liver regeneration after partial hepatectomy in mice

To clarify the roles of innate immune cells in liver regeneration, here, we investigated the alteration in regenerative responses after partial hepatectomy (PH) under selective depletion of natural killer (NK) and/or NKT cells. Male, wild-type (WT; C57Bl/6), and CD1d-knockout (KO) mice were injected with anti-NK1.1 or anti-asialo ganglio-N-tetraosylceramide (GM1) antibody and then underwent the 70% PH. Regenerative responses after PH were evaluated, and hepatic expression levels of cytokines and growth factors were measured by real-time RT-PCR and ELISA. Phosphorylation of STAT3 was detected by Western blotting. Depletion of both NK and NKT cells with an anti-NK1.1 antibody in WT mice caused drastic decreases in bromodeoxyuridine uptake, expression of proliferating cell nuclear antigen, and cyclin D1, 48 h after PH. In mice given NK1.1 antibody, increases in hepatic TNF-α, IL-6/phospho-STAT3, and hepatocyte growth factor (HGF) levels following PH were also blunted significantly, whereas IFN-γ mRNA levels were not different. CD1d-KO mice per se showed normal liver regeneration; however, pretreatment with an antiasialo GM1 antibody to CD1d-KO mice, resulting in depletion of both NK and NKT cells, also blunted regenerative responses. Collectively, these observations clearly indicated that depletion of both NK and NKT cells by two different ways results in impaired liver regeneration. NK and NKT cells most likely upregulate TNF-α, IL-6/STAT3, and HGF in a coordinate fashion, thus promoting normal regenerative responses in the liver.

Depletion of Invariant NKT Cells Reduces Inflammation-Induced Preterm Delivery in Mice

This study sought to determine whether invariant NKT (iNKT) cells play an essential role in inflammation-induced preterm delivery. Preterm delivery and fetal death rates were determined in wild-type (WT) C57BL/6 mice and iNKT cell-deficient Jα18(-/-) mice injected i.p. with LPS. The percentages of decidual immune cells, including activated subsets, and costimulatory molecule expression were analyzed by flow cytometry. Th1 and Th2 cytokine production in the culture supernatants of decidual mononuclear cells was measured by ELISA. To some extent, Jα18(-/-) mice were resistant to LPS-induced preterm delivery. The proportions of decidual CD3(+) and CD49b(+) cells were slightly lower in Jα18(-/-) mice than in WT Jα18(+/+) mice, whereas almost no CD3(+)CD49b(+) cells could be found in Jα18-null mice. The percentages of activated decidual DCs, T cells, and NK cells were significantly lower in LPS-treated Jα18(-/-) mice than in WT mice. The CD40, CD80, and CD86 expression levels on decidual CD11c(+) cells from Jα18(-/-) mice were also significantly lower than in WT mice. Mean concentrations of Th1 cytokines IFN-γ and IL-12p70 in the culture supernatants of decidual mononuclear cells from LPS-treated Jα18(-/-) mice were apparently lower than those of LPS-induced WT mice. Additionally, the proportions of activated CD11c(+) cells, CD3(+) cells, and CD49b(+) cells in LPS-induced preterm delivery mice were strikingly higher in both WT and null mice when compared with the control PBS group and LPS-injected but normally delivered mice. Our results suggest that iNKT cells may play an essential role in inflammation-induced preterm birth.

Vγ4 γδ T Cell-Derived IL-17A Negatively Regulates NKT Cell Function in Con A-Induced Fulminant Hepatitis

Con A-induced fulminant hepatitis is a well-known animal model for acute liver failure. However, the role of γδ T cells in this model is undefined. In this report, using TCR δ(-/-) mice, we demonstrated a protective role of γδ T cells in Con A-induced hepatitis model. TCR δ(-/-) mice showed significantly decreased levels of IL-17A and IL-17F in the Con A-treated liver tissue, and reconstitution of TCR δ(-/-) mice with wild-type (Wt), but not IL-17A(-/-), γδ T cells significantly reduced hepatitis, strongly suggesting a critical role of IL-17A in mediating the protective effect of γδ T cells. Interestingly, only Vγ4, but not Vγ1, γδ T cells exerted such a protective effect. Furthermore, depletion of NKT cells in TCR δ(-/-) mice completely abolished hepatitis, and NKT cells from Con A-challenged liver tissues of TCR δ(-/-) mice expressed significantly higher amounts of proinflammatory cytokine IFN-γ than those from Wt mice, indicating that γδ T cells protected hepatitis through targeting NKT cells. Finally, abnormal capacity of IFN-γ production by NKT cells of TCR δ(-/-) mice could only be downregulated by transferring Wt, but not IL-17(-/-), Vγ4 γδ T cells, confirming an essential role of Vγ4-derived IL-17A in regulating the function of NKT cells. In summary, our report thus demonstrated a novel function of Vγ4 γδ T cells in mediating a protective effect against Con A-induced fulminant hepatitis through negatively regulating function of NKT cells in an IL-17A-dependent manner, and transferring Vγ4 γδ T cells may provide a novel therapeutic approach for this devastating liver disease.

Vaccination with photodynamic therapy-treated macrophages induces highly suppressive T-regulatory cells

The present study explores whether photodynamic therapy (PDT)-induced apoptosis can increase the number of tolerogenic regulatory T cells (Treg) and limit collateral tissue damage. BALB/c mice were vaccinated subcutaneously three times with PDT-induced apoptotic or thaw-frozen, necrotic non-infected autologous macrophages (MΦ). Two weeks after the last vaccination, mice were infected intradermally with 10(6) promastigotes of Leishmania major. Mice that received PDT-induced apoptotic MΦ had fewer parasites and higher numbers of Treg than mice vaccinated with thaw-frozen necrotic MΦ or phosphate-buffered saline (PBS). Interleukin (IL)-4 and IL-6 were significantly suppressed, while IL-10 was increased in mice that received the PDT-induced apoptotic MΦ. The role of Treg in this process was confirmed through Treg transfer from vaccinated to naïve mice. Mice receiving CD4(+) CD25(+) cells from mice vaccinated with PDT-induced apoptotic MΦ showed smaller lesions 3 weeks after infection and lower parasitic burdens than mice that received Tregs from mice of thaw-frozen necrotic MΦ or PBS groups. These changes were mediated by the depletion of CD3(+) CD8(+) and NKT cells and increased levels of IL-12p70 and interferon-γ, IL-10, and TGF-β in the cutaneous leishmaniasis lesions. Vaccination with apoptotic MΦ-induced tolerogenic Treg cells that limited collateral tissue damage and diminished parasitic burden.

1084 CYCLIN El AND Dl CAN DRIVE LIVER REGENERATION IN MICE WITHOUT CDK2

Background and Aims: Liver regeneration is impaired in obese, diabetic rodents developing spontaneous steatohepatitis such as ob/ob and KK-A mice, in which hepatic NKT cells are depleted. In this study, we investigated the differences in hepatic regeneration after partial hepatectomy (PH) in mice selectively depleted NK and/or NKT cells. Methods: Male, 12 week-old CD1d-knockout (KO) mice, which lack NKT cells systemically, and wild type (WT; C57Bl/6) mice were used. Some mice were pretreated with NK1.1 or asialo-GM1 antibody 24hr prior to experiments to deplete NK/NKT cells or NK cells alone, respectively. Mice underwent the 2/3 PH, and the uptake of BrdU and the expression of PCNA in hepatocyte nuclei were detected by immunohistochemistry. Hepatic expression levels of cyclin D1 and IFNg mRNA were analyzed quantitatively by Western blotting and real time RT-PCR, respectively. Results: In CD1d-KO mice, BrdU uptake and PCNA expression were almost similar to those in WT mice 48hr after PH, the labeling indices being nearly 20% and 30%, respectively. In sharp contrast, both parameters after PH was decreased remarkably in WT mice pretreated with an NK1.1 antibody, values reaching only 1.7% and 11.9%, respectively (P < 0.01 vs. WT after PH). Further, expression of cylin D1 in the liver 48hr after PH was nearly normal in CD1d-KO mice, but the levels were almost completely blunted in mice given an NK1.1 antibody. Interestingly, CD1d-KO mice given an asialoGM1 antibody showed impaired regenerative responses as similar to WT mice given an NK1.1 antibody. Hepatic IFNg mRNA was elevated nearly 5-fold in WT mice 6hr after PH, which was not affected by pretreatment with an NK1.1 antibody. Conclusions: These findings clearly indicated that liver regeneration is markedly impaired when both NKT and NK cells are depleted in two different preparations. NK cell-function under regeneration appears to be paradoxical in the presence or absence of NKT cells, and it is unlikely that IFNg plays a regulatory role in regeneration failure caused by simultaneous depletion of NK and NKT cells. It is therefore concluded that NKT and NK cells are coordinately involved in normal regenerative responses in the liver. 1084 CYCLIN E1 AND D1 CAN DRIVE LIVER REGENERATION IN MICE WITHOUT CDK2 W. Hu, Y.A. Nevzorova, J.R. Nowak, U. Haas, N. Moro, Y. Geng, P. Sicinski, M. Barbacid, C. Trautwein, C. Liedtke. Department of Medicine III, University Hospital Aachen, RWTH Aachen University, Aachen, Germany; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA; Centro Nacional de Investigaciones Oncologicas (CNIO), Madrid, Spain E-mail: whu@ukaachen.de

Dietary fatty acids modulate antigen presentation to hepatic NKT cells in nonalcoholic fatty liver disease

Dietary fatty acids are major contributors to the development and progression of insulin resistance and nonalcoholic fatty liver disease (NAFLD). Dietary fatty acids also alter hepatic NKT cells that are activated by antigens presented by CD1d. In the current study, we examine the mechanism of dietary fatty acid induced hepatic NKT cell deficiency and its causal relationship to insulin resistance and NAFLD. We discover that dietary saturated fatty acids (SFA) or monounsaturated fatty acids (MUFA), but not polyunsaturated fatty acids (PUFA), cause hepatic NKT cell depletion with increased apoptosis. Dietary SFA or MUFA also impair hepatocyte presentation of endogenous, but not exogenous, antigen to NKT cells, indicating alterations of the endogenous antigen processing or presenting pathway. In vitro treatment of normal hepatocytes with fatty acids also demonstrates impaired ability of CD1d to present endogenous antigen by dietary fatty acids. Furthermore, dietary SFA and MUFA activate the NFkappaB signaling pathway and lead to insulin resistance and hepatic steatosis. In conclusion, both dietary SFA and MUFA alter endogenous antigen presentation to hepatic NKT cells and contribute to NKT cell depletion, leading to further activation of inflammatory signaling, insulin resistance, and hepatic steatosis.

The BH3-Only Protein Bid Does Not Mediate Death-Receptor-Induced Liver Injury in Obstructive Cholestasis

The accumulation of bile acids during obstructive cholestasis causes liver injury and fibrosis, which is at least partly mediated by the death receptors Tumor necrosis factor-related apoptosis-inducing ligand, Tumor necrosis factor-alpha, and Fas. The BH3-interacting domain death agonist Bid is a critical mediator of death receptor-induced apoptosis in hepatocytes. Our aim for this study was, therefore, to elucidate whether Bid also mediates death receptor-induced liver injury in obstructive cholestasis. Overall, survival and various aspects of liver injury were analyzed in wild-type and Bid(-/-) mice after bile duct ligation (BDL), a commonly used model to study obstructive cholestasis in mice. Liver injury was examined at 3, 7, and 14 days after BDL. Loss of Bid did not affect the number of bile infarcts, serum aspartate aminotransferase values, or animal survival. Processing of procaspase-3 and procaspase-9, and caspase-3 enzyme activities, were not detectable in either group, and Bid(-/-) mice displayed the same pattern of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling positive hepatocytes as wild-type controls following BDL. In contrast to Fas-receptor deficient lpr mice, hepatic fibrosis and the inflammatory response was not affected by loss of Bid. Together, these data suggest that Bid is not a downstream target of death receptors in obstructive cholestasis and does not significantly contribute to bile acid induced liver injury and fibrosis.

Contrasting roles for Vα14+natural killer T cells in a viral model for multiple sclerosis

Most natural killer (NK) T cells express an invariant Valpha14 T-cell receptor. To explore the contribution of NKT cells in an animal model for multiple sclerosis, Theiler's murine encephalomyelitis virus (TMEV) infection, TMEV-infected mice were treated with Valpha14 antibody. Treatment during the early stage of infection delayed the onset of demyelinating disease with higher interleukin-4 production, whereas administration during the late stage or weekly resulted in more severe demyelination with enhanced virus persistence. The effect of in vivo depletion of NKT cells differed depending on the stage of infection, suggesting contrasting roles for NKT cells over the disease course.

Probiotics improve high fat diet-induced hepatic steatosis and insulin resistance by increasing hepatic NKT cells

Dietary factors and intestinal bacteria play an important role in the rapidly increasing incidence of obesity and its associated conditions, such as steatosis and insulin resistance. In the current study, we evaluated the effect of probiotics, and their mechanisms on diet-induced obesity, steatosis and insulin resistance. Wild-type male C57BL6 mice were fed either normal or high fat diets. Some mice received VSL#3 probiotics. Animal weight, hepatic steatosis, insulin resistance, and their relationship to hepatic Natural Killer T cells (NKT) cell number and inflammatory signaling were evaluated. High fat diet induced a depletion of hepatic NKT cells thus leading to insulin resistance and steatosis. Oral probiotic treatment significantly improved the high fat diet-induced hepatic NKT cell depletion, insulin resistance and hepatic steatosis. This effect was NKT cell dependant, resulted from the attenuation of the tumor necrosis factor-alpha and IkappaB kinase inflammatory signaling, and led to an improved sensitivity in insulin signaling. Probiotics improve high fat diet-induced steatosis and insulin resistance. These effects of probiotics are likely due to increased hepatic NKT cell numbers and reduced inflammatory signaling.

Inflammation and drug hepatotoxicity: Aggravation of injury or clean-up mission?

BACKGROUND & AIMS Inflammatory mediators released by nonparenchymal inflammatory cells in the liver have been implicated in the progression of acetaminophen (APAP) hepatotoxicity. Among hepatic nonparenchymal inflammatory cells, we examined the role of the abundant natural killer (NK) cells and NK cells with T-cell receptors (NKT cells) in APAP-induced liver injury. METHODS C57BL/6 mice were administered a toxic dose of APAP intraperitoneally to cause liver injury with or without depletion of NK and NKT cells by anti-NK1.1 monoclonal antibody (MAb). Serum alanine transaminase (ALT) levels, liver histology, hepatic leukocyte accumulation, and cytokine/chemokine expression were assessed. RESULTS Compared with APAP-treated control mice, depletion of both NK and NKT cells by anti-NK1.1 significantly protected mice from APAP-induced liver injury, as evidenced by decreased serum ALT level, improved survival of mice, decreased hepatic necrosis, inhibition of messenger RNA (mRNA) expression for interferon-gamma (IFN-gamma), Fas ligand (FasL), and chemokines including KC (Keratinocyte-derived chemokine); MIP-1 alpha (macrophage inflammatory protein-1 alpha); MCP-1 (monocyte chemoattractant protein-1); IP-10 (interferon-inducible protein); Mig (monokine induced by IFN-gamma) and decreased neutrophil accumulation in the liver. Hepatic NK and NKT cells were identified as the major source of IFN-gamma by intracellular cytokine staining. APAP induced much less liver injury in Fas-deficient (lpr) and FasL-deficient (gld) mice compared with that in wild-type mice. CONCLUSIONS NK and NKT cells play a critical role in the progression of APAP-induced liver injury by secreting IFN-gamma, modulating chemokine production and accumulation of neutrophils, and up-regulating FasL expression in the liver, all of which may promote the inflammatory response of liver innate immune system, thus contributing to the severity and progression of liver injury downstream of the metabolism of APAP and depletion of reduced glutathione (GSH) in hepatocytes.