Cytokine production and killer activity of NK/T-NK cells derived with IL-2, IL-15, or the combination of IL-12 and IL-18

Ex vivo Culture with Interleukin (IL)-12 Improves CD8+ T-Cell Adoptive Immunotherapy for Murine Leukemia Independent of IL-18 or IFN-γ but Requires Perforin

In animal models and clinical trials, adoptive transfer of activated, antigen-specific CD8+ T cells mediates tumor regression in a cell dose-dependent manner. The cytokine interleukin (IL)-12 promotes CD8+ T-cell cytotoxicity and, with IL-18, synergistically up-regulates IFN-γ release. We have shown that culturing CD8+ T cells ex vivo with IL-12 and IL-18 enhanced antitumor responses in vivo and in vitro using a model of C1498/ovalbumin, a murine acute myeloid leukemia cell line expressing the antigen ovalbumin. Activated ovalbumin-specific CD8+ T cells cultured with IL-12, IL-18, both, or neither were assayed for antigen-specific cytokine production and cytolytic activity and adoptively transferred to C57BL/6 mice with established tumors. Maximal IFN-γ release occurred after T-cell culture with IL-12 and IL-18. Tumor-specific in vitro cytotoxicity was enhanced by IL-12, unaffected by addition of IL-18, and abrogated in perforin-deficient T cells irrespective of cytokine exposure. T cells cultured with IL-12 more effectively eliminated tumors, and addition of IL-18 did not further augment responses. IFN-γ-deficient CD8+ T cells showed effective antitumor activity that was enhanced by IL-12 with or without IL-18. Perforin-deficient CD8+ T cells were poor mediators of antitumor activity, though, and showed no improvement after culture with IL-12 and/or IL-18. Thus, ex vivo culture with IL-12 was sufficient to augment antigen-specific in vitro cytotoxicity and antitumor activity in vivo in an IFN-γ-independent but perforin-dependent manner. Ex vivo culture with IL-12 may improve CD8+ T-cell immunotherapy of cancer in the absence of donor cell–derived IFN-γ via perforin-mediated cytolysis. (Cancer Res 2006; 66(9): 4913-21)

B cell induction of IL-13 expression in NK cells: role of CD244 and SLAM-associated protein

NK cells are an important component of the innate immune system that can also interact with B cells in a mutually productive manner. We have previously shown that activated B cells can induce NK cells to up-regulate their secretion of IFN-gamma. In this study, we show that B cells, and, particularly, marginal zone B cells, can, in addition, induce NK cells via direct cell-cell interactions to express mRNA encoding the Th2 cytokine IL-13. The induction of NK cell IL-13 mRNA expression requires the ligation of the CD244 receptor by the CD48 ligand on B cells via signaling pathways that depend upon expression of the X-linked lymphoproliferative disease gene product, SH2D1A/DSHP/SAP (SLAM-associated protein, or SAP) in NK cells. Thus, the positive signals attributed to the B cell activation of CD244 on murine NK cells appears to be more similar to the activity of CD244 on human cells. The induction of IL-13 mRNA by B cells may account for the effect of NK cells on the generation of Th2-type responses in the presence of some adjuvants.

Interaction of mouse dendritic cells and malaria-infected erythrocytes: uptake, maturation, and antigen presentation

Consistent with their seminal role in detecting infection, both mouse bone marrow-derived and splenic CD11c+ dendritic cells (DCs) exhibited higher levels of uptake of Plasmodium chabaudi-parasitized RBCs (pRBCs) than of noninfected RBCs (nRBCs) as determined by our newly developed flow cytometric technique using the dye CFSE to label RBCs before coculture with DCs. To confirm that expression of CFSE by CD11c+ cells following coculture with CFSE-labeled pRBCs represents internalization of pRBC by DCs, we showed colocalization of CFSE-labeled pRBCs and PE-labeled CD11c+ DCs by confocal fluorescence microscopy. Treatment of DCs with cytochalasin D significantly inhibited the uptake of pRBCs, demonstrating that uptake is an actin-dependent phagocytic process. The uptake of pRBCs by splenic CD11c+ DCs was significantly enhanced after infection in vivo and was associated with the induction of DC maturation, IL-12 production, and stimulation of CD4+ T cell proliferation and IFN-gamma production. These results suggest that DCs selectively phagocytose pRBCs and present pRBC-derived Ags to CD4+ T cells, thereby promoting development of protective Th1-dependent immune responses to blood-stage malaria infection.

The liver as an immunological organ

The liver is a unique anatomical and immunological site in which antigen-rich blood from the gastrointestinal tract is pressed through a network of sinusoids and scanned by antigen-presenting cells and lymphocytes. The liver's lymphocyte population is selectively enriched in natural killer and natural killer T cells which play critical roles in first line immune defense against invading pathogens, modulation of liver injury and recruitment of circulating lymphocytes. Circulating lymphocytes come in close contact to antigens displayed by endothelial cells, Kupffer cells and liver resident dendritic cells in the sinusoids. Circulating lymphocytes can also contact hepatocytes directly, because the sinusoidal endothelium is fenestrated and lacks a basement membrane. This unique anatomy of the liver may facilitate direct or indirect priming of lymphocytes, modulate the immune response to hepatotrophic pathogens and contribute to some of the unique immunological properties of this organ, particularly its capacity to induce antigen-specific tolerance.

Interactions Between Human Mesenchymal Stem Cells and Natural Killer Cells

Mesenchymal stem cells (MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for regenerative medicine. They possess unique immunomodulatory properties, being capable of suppressing T-cell responses and modifying dendritic cell differentiation, maturation, and function, whereas they are not inherently immunogenic, failing to induce alloreactivity to T cells and freshly isolated natural killer (NK) cells. To clarify the generation of host immune responses to implanted MSCs in tissue engineering and their potential use as immunosuppressive elements, the effect of MSCs on NK cells was investigated. We demonstrate that at low NK-to-MSC ratios, MSCs alter the phenotype of NK cells and suppress proliferation, cytokine secretion, and cyto-toxicity against HLA-class I- expressing targets. Some of these effects require cell-to-cell contact, whereas others are mediated by soluble factors, including transforming growth factor-beta1 and prostaglandin E2, suggesting the existence of diverse mechanisms for MSC-mediated NK-cell suppression. On the other hand, MSCs are susceptible to lysis by activated NK cells. Overall, these data improve our knowledge of interactions between MSCs and NK cells and consequently of their effect on innate immune responses and their contribution to the regulation of adaptive immunity, graft rejection, and cancer immunotherapy.

Early interactions between blood-stage plasmodium parasites and the immune system

Accumulating evidence provides strong support for the importance of innate immunity in shaping the subsequent adaptive immune response to blood-stage Plasmodium parasites, the causative agents of malaria. Early interactions between blood-stage parasites and cells of the innate immune system, including dendritic cells, monocytes/macrophages, natural killer (NK) cells, NKT cells, and gamma6 T cells, are important in the timely control of parasite replication and in the subsequent elimination and resolution of the infection. The major role of innate immunity appears to be the production of immunoregulatory cytokines, such as interleukin (IL)-12 and interferon (IFN)-gamma, which are critical for the development of type 1 immune responses involving CD4+ Thl cells, B cells, and effector cells which mediate cell-mediated and antibody-dependent adaptive immune responses. In addition, it is likely that cells of the innate immune system, especially dendritic cells, serve as antigen-presenting cells. Here, we review recent data from rodent models of blood-stage malaria and from human studies, and outline the early interactions of infected red blood cells with the innate immune system. We compare and contrast the results derived from studies in infected laboratory mice and humans. These host species are sufficiently different with respect to the identity of the infecting Plasmodium species, the resulting pathologies, and immune responses, particularly where the innate immune response is concerned. The implications of these findings for the development of an effective and safe malaria vaccine are also discussed.

Effect of IL-21 on NK cells derived from different umbilical cord blood populations

IL-21 plays a role in the proliferation and maturation of NK cells developed from hematopoietic stem cells. In this study, we found that IL-21, in the presence of physiological concentration of hydrocortisone (HC), has a significant impact on the functions of NK cells derived from umbilical cord blood (CB) populations. We demonstrate that IL-21, in combination with Flt3-ligand, IL-15 and HC, induces high proliferative responses and, apart from enhancing NK-mediated cytotoxicity, it also induces a significant increase in lymphokine-activated killer activity of CB/CD34+-derived CD56+ cells. In addition, IL-21 induced changes in the CD56+ cell cytokine secretion profile. Thus, we observed increased levels of IL-10 and granulocyte macrophage colony-stimulating factor, whereas tumor necrosis factor-alpha levels decreased. IFN-gamma production was also modified by IL-21, depending on the presence or absence of IL-18. CB/CD34+ cells did not express the IL-21R ex vivo, but receptor expression was induced during their commitment to differentiation into CD56+ cells. Our data ascribe to IL-21 an essential role on NK cell development and function under conditions similar to the in vivo CB microenvironment.

NK cells: elusive players in autoimmunity

Natural killer (NK) cells were once regarded as relatively simple cells of the innate immune system. However, they are now revealing themselves as multifunctional regulatory cells that are present throughout the body. The role of NK cells in autoimmunity is attracting increased attention, although the picture is clouded by a conflicting literature that presents disease-promoting as well as disease-protective roles. In this review, we discuss how NK cells might use these dual roles, and suggest that future studies should focus on the impact of the anatomical localization of NK cells as well as the cytokine environment in which NK cells act in individual autoimmune diseases.

A potential role for hydrocortisone in the positive regulation of IL-15–activated NK-cell proliferation and survival

Although glucocorticoids (GCs) have been described as acting mainly as anti-inflammatory and immunosuppressive drugs, they may also positively influence the immune system. In the present study, we demonstrate for the first time that hydrocortisone (HC), in synergy with interleukin-15 (IL-15), induces a dramatic increase in the expansion of peripheral blood–derived CD56+ cells, favoring the preferential outgrowth of classical natural killer (CD56+CD3– NK) over CD56+CD3+ natural killer T (NKT) cells. HC plus IL-15–driven CD56+ cells exhibited an increased potential for cytokine production with no impairment in their NK- and lymphokine-activated killer (LAK) activities. Elevated levels of GC-induced leucine zipper protein (GILZ) messenger RNA (mRNA) were detected in both NK and NKT cells cultured with HC and IL-15, in comparison to IL-15 alone. Phosphorylation status of signal transducer and activator of transcription 5 (STAT5) was not affected by the presence of HC in either of the populations. On the contrary, HC differentially affected the IL-2/IL-15R β- and γ-chain surface expression and the phosphorylation levels of extracellular signal-regulated kinases 1/2 (ERK1/2) in IL-15–activated NK and NKT cells. Our data ascribe a novel role to GCs on mature NK-cell expansion and function and open new perspectives for their use in cellular adoptive cancer immunotherapy.

Interleukin-15 enhances innate and adaptive immune responses to blood-stage malaria infection in mice

Compared to C57BL/6 wild-type mice, interleukin-15(-/-) (IL-15(-/-)) mice showed delayed clearance of Plasmodium chabaudi AS infection, lower type 1 cytokine production, impaired dendritic cell and NK cell functions, and lower titers of malaria-specific antibodies. Thus, IL-15 supports early control and timely resolution of blood-stage malaria through promotion of Th1-dependent innate and adaptive immune responses.

Targeting IL-2 to the endoplasmic reticulum confines autocrine growth stimulation to NK-92 cells

OBJECTIVE

Anti-tumor effects mediated by adoptively transferred natural killer (NK) cells are dependent on the presence of interleukin-2 (IL-2). IL-2 is considered to be a survival factor for NK cells and an enhancer of their cytotoxic potential. However, systemic administration of IL-2 is frequently impeded by undesirable side effects, such as high toxicity and nonlocalized administration. Genetic modification of NK cells expressing IL-2 in a localized and controlled manner could be a powerful tool for overcoming these obstacles.

METHODS

Consequently, we have cloned the IL-2 gene using PCR and designed constructs that target IL-2 to specific subcellular compartments. The IL-2-dependent NK-92 cell line was used to verify the functionality of the subcellularly targeted IL-2 constructs.

RESULTS

IL-2 targeted specifically to the endoplasmic reticulum (ER) was sufficient to support growth of NK-92 cells. In such cell lines, IL-2 was verified to be localized to the ER. IL-2 was not detected in the supernatant and growth of non-IL-2-modified NK-92 cells was not supported during coculturing experiments. IL-2-transduced NK-92 cell lines showed comparable functional activity and cytotoxicity to parental NK-92 cells.

CONCLUSION

We demonstrate the ability of ER-retained IL-2 to provide autocrine growth stimulation to NK-92 cells, without secretion of the cytokine to the extracellular compartment. Therapy with IL-2 gene-modified autoactivating NK cells may avoid side effects imposed by exogenously administered IL-2.

Changes in hippocampal IL-15, related cytokines, and neurogenesis in IL-2 deficient mice

Previous studies have demonstrated that interleukin-2 knockout (KO) mice exhibit alterations in hippocampal cytoarchitecture. Several lines of evidence suggest that these variations may result from immune dysregulation and/or autoimmunity. Thus, this study sought to compare adult IL-2 KO mice and wild-type littermates (8-12 weeks of age), the age where differences in hippocampal cytoarchitecture have previously been observed, for differences in measures of neuroimmunological status in the hippocampus. Furthermore, because IL-15 shares the same receptor subunits for signal transduction as IL-2 (IL-2/15Rbeta and gammac) that are enriched in the hippocampus and may induce inflammatory processes in IL-2 KO mice, we sought to test the hypothesis that IL-15 is elevated in the hippocampus of IL-2 KO mice. Compared to wild-type mice, IL-2 KO mice exhibited increased hippocampal protein concentrations of IL-15 as well as IL-12, IP-10, and MCP-1. These cytokine changes, however, did not correlate with levels in the peripheral circulation, and there were no T cells or an increase in MHCII-positive microglia in the hippocampus of IL-2 KO mice. Since elevated levels of certain inflammatory cytokines may impair hippocampal neurogenesis, we also tested the hypothesis that changes in neuroimmunological status would be associated with reductions in neurogenesis of neurons in the dentate gyrus of IL-2 KO mice. Contrary to this hypothesis, compared to wild-type mice, male IL-2 KO mice exhibited increased neurogenesis in both the infrapyramidal and suprapyramidal limbs of the granule cell layer of the dentate gyrus, differences that were not observed between females. These findings indicate that IL-2 gene deletion alters the neuroimmunological status of the mouse hippocampus through a dysregulation of cytokines produced by CNS cells, and in males, these changes are associated with increased hippocampal neurogenesis.

Interleukin-32: a cytokine and inducer of TNFalpha

We describe the gene structure, regulation, signal transduction. and functions of a cytokine, interleukin (IL)-32. An IL-18 unresponsive cell was converted to a responsive cell by transfection of the IL-18 receptor beta chain, and IL-18-induced microarray revealed high expression of a cytokine-like gene. Although IL-32 does not share sequence homology with known cytokine families, IL-32 induces various cytokines, human TNFalpha, and IL-8 in THP-1 monocytic cells as well as mouse TNFalpha and MIP-2 in Raw macrophage cells. IL-32 activates typical cytokine signal pathways of nuclear factor-kappa B (NF-kappaB) and p38 mitogen-activated protein kinase. IL-32 mRNA is highly expressed in immune tissue rather than other tissues. Human IL-32 exists as four splice variants, and IL-32 from other species were found as expressed sequence tag clones in the databank. Induced in human peripheral lymphocyte cells after mitogen stimulation, in human epithelial cells by IFNgamma, and in NK cells after exposure to the combination of IL-12 plus IL-18, IL-32 may play a role in inflammatory/autoimmune diseases.

Atherosclerotic abdominal aortic aneurysm and the interaction between autologous human plaque-derived vascular smooth muscle cells, type 1 NKT, and helper T cells

Immune cell infiltration, vascular smooth muscle cell (VSMC) proliferation, and apoptosis are pathological hallmarks of atherosclerosis. The multifocal, chronic, and inflammatory nature of this disease of the cardiovascular system complicates targeted cellular therapy and emphasizes the need to understand the role and interaction of immune cells with VSMCs. We characterized the immune cell subsets present in human atherosclerotic tissue derived from atherosclerotic abdominal aortic aneurysm (AAA) and expanded them to study their interaction with autologous plaque-derived VSMCs in vitro. We show here that apart from T lymphocytes, plaque infiltrates consist of lots of NK cells and significant proportions of NKT cells that express T cell receptor (TCR) alphabeta, CD4, and the NK markers CD56 and CD161. The infiltrates are predominantly IFN-gamma-producing Type 1 lymphoid cells. When cocultured, the T and NKT cells adhere to VSMCs. CD4+ T cells enhance VSMC proliferation. VSMCs in turn enhance CD4+CD161+ NKT but not CD4+ or CD8+ T cell proliferation. CD4+CD161+ NKT cells inhibit VSMC proliferation by inducing apoptosis. Our results suggest that the interactions of Type 1 CD4+ T and CD4+CD161+ NKT cells with VSMCs may regulate VSMC proliferation and death respectively in atherosclerosis and the balance of these interactions could determine plaque stability.

Interleukins 2 and 15 Regulate Ets1 Expression via ERK1/2 and MNK1 in Human Natural Killer Cells

Interleukins (IL)-2 and IL-15 regulate natural killer (NK) cell proliferation, survival, and cytolytic activity. Ets1 is a transcription factor expressed early in NK cell differentiation. Because IL-2Rbeta, IL-2Rgamma, IL-15, and Ets1 knock-out mice similarly lack NK cells, we explored a molecular connection between IL-2R signaling and Ets1. Here we report the post-transcriptional regulation of Ets1 by IL-2R signaling in human NK cells. IL-2 and IL-15 stimulation leads to increased Ets1 protein levels with no significant change in mRNA levels. Pulse and pulse-chase experiments show that IL-2 stimulation results in both a marked increase in the nascent translation of Ets1 and an increased protein half-life. Pharmacological inhibition of MEK specifically blocks IL-2- and IL-15-induced translation, whereas p38, phosphatidylinositol 3-kinase, and mTOR inhibitors had no effect on Ets1 levels. Fli1, an Ets family member, exhibited a different mechanism of regulation, illustrating the specificity of IL-2R beta and gamma subunit signaling on the regulation of Ets1 expression. Expression of a dominant negative form of MNK1, a regulator of the translation initiation factor eIF4E, blocks the expression of Ets1 as do the dominant negative forms of the common IL-2R beta and gamma chains. Expression of Ets1 is regulated similarly in normal peripheral human NK cells. Taken together, our findings provide a direct link between IL-2R subunit signaling and Ets1 expression and helps to explain the interdependence of the IL-2R subunits and Ets1 for NK cell development and function.

Anatomy of a murder—signal transduction pathways leading to activation of natural killer cells

Natural killer (NK) cells control the early phases of viral infections, modulate antigen-specific immune responses, and participate in the rejection of tumours and bone marrow grafts. A fine balance between inhibitory and activating receptors tightly regulates NK cell activation. Biochemical studies in human cell lines and primary cells have revealed some of the activating NK cell signalling pathways, however animal models are instrumental to understand the physiological implications of these findings for immune responses in vivo. Gene targeting in mice and biochemical studies in cells are helping to dissect out the various signal transduction pathways that control NK cell activation. A clearer view of these pathways may eventually help designing more effective immune therapies based on the use of NK cells.

Mechanisms of Superior Anti-Tumor Cytotoxic Response of Interleukin 15-Induced Lymphokine-Activated Killer Cells

Interleukin (IL) 15 is one of the main cytokines controlling cytotoxic lymphocyte survival and growth. Despite its receptor and functional similarity to IL-2, IL-15 affects a wider target cell population and utilizes different mechanisms in cell activation. The role of IL-15 in lymphokine-activated killer (LAK) cell generation in vitro and potential mechanisms of cytotoxicity compared with equivalent low concentration of IL-2 with or without mitogens (phytohemoglutinin (PHA) and anti-CD3 antibody) have been investigated in this study. IL-15 treatment resulted in moderate cell proliferation over 7 days, whereas IL-2 treatment was associated with decreased cell numbers. Unlike IL-2 in combination with mitogens, IL-15 caused increases in both cytotoxic T lymphocytes (CTL) and CD56 LAK cells, particularly cytokine-induced killer and cytolytic natural killer T-cell (CNK-T) subpopulations, which are known to be highly effective in cytotoxicity. IL-15 also increased overall perforin and tumor necrosis factor-alpha expression and more prominently in CTLs. Consequently, IL-15 resulted in superior cytotoxicity against two different NK-sensitive (human K-562 and murine YAC-1) and LAK-sensitive (human Daudi and Raji) cell lines compared with other cytokine combinations. There was also no contribution of mitogens to IL-2-induced cytotoxicity. In conclusion, IL-15 at the concentration of 10 ng/mL used in this study causes moderate proliferation and superior cytotoxicity of LAK cells in vitro that was associated with induction of a specific LAK cell subpopulation profile and related cellular killing mechanisms. These results are encouraging for potential use of IL-15 as part of immunotherapy.

Interleukin-15, as Interferon-gamma, Induces the Killing of Leishmania infantum in Phorbol-Myristate-Acetate-Activated Macrophages Increasing Interleukin-12

The potential leishmanicidal activity of interleukin-15 (IL-15) was examined while priming with the cytokine phorbol-myristate-acetate (PMA)-activated macrophages and infecting them with Leishmania infantum parasites. The activation of macrophage cultures with IL-15 determined a significant anti-leishmanial activity, comparable with that induced by interferon-gamma (IFN-gamma). The killing of Leishmania in macrophages primed with IL-15, as well as with IFN-gamma, was followed by an increase in the IL-12 synthesis. The neutralization of IL-15 or IFN-gamma, by specific monoclonal antibodies (MoAb) caused a significant reduction in leishmanicidal activity. Furthermore, in PMA-activated macrophages, the neutralization of IL-12 production by a specific anti-IL-12 MoAb reduced leishmanicidal activity induced by IL-15 and IFN-gamma. Data indicate that IL-15 could have a role as an activator of leishmanicidal activity, directly or indirectly, by inducing IL-12 production.

Thalidomide salvage therapy following allogeneic stem cell transplantation for multiple myeloma: a retrospective study from the Intergroupe Francophone du Myélome (IFM) and the Société Française de Greffe de Moelle et Thérapie Cellulaire (SFGM-TC)

Thalidomide is effective in multiple myeloma (MM), even in patients who have relapsed after high-dose therapy. A potent graft-versus-myeloma (GVM) effect can be induced against MM after allogeneic stem cell transplantation (allo-SCT). In all, 31 MM patients received thalidomide as a salvage therapy after progression following allo-SCT. The median maximum daily dose of thalidomide was 200 mg (range, 50-600). Thalidomide had to be discontinued in six patients (19%) because of toxicity. In all, nine patients (29%; 95% CI, 13-45) achieved an objective response with thalidomide therapy (six partial and three very good partial responses, VGPR). Five patients developed graft-versus-host disease (GVHD) after thalidomide therapy, including the three patients achieving a VGPR. These data demonstrate that thalidomide is potentially effective in MM patients failing allo-SCT.

TL1A synergizes with IL-12 and IL-18 to enhance IFN-gamma production in human T cells and NK cells

TL1A, a recently described TNF-like cytokine that interacts with DR3, costimulates T cells and augments anti-CD3 plus anti-CD28 IFN-gamma production. In the current study we show that TL1A or an agonistic anti-DR3 mAb synergize with IL-12/IL-18 to augment IFN-gamma production in human peripheral blood T cells and NK cells. TL1A also enhanced IFN-gamma production by IL-12/IL-18 stimulated CD56(+) T cells. When expressed as fold change, the synergistic effect of TL1A on cytokine-induced IFN-gamma production was more pronounced on CD4(+) and CD8(+) T cells than on CD56(+) T cells or NK cells. Intracellular cytokine staining showed that TL1A significantly enhanced both the percentage and the mean fluorescence intensity of IFN-gamma-producing T cells in response to IL-12/IL-18. The combination of IL-12 and IL-18 markedly up-regulated DR3 expression in NK cells, whereas it had minimal effect in T cells. Our data suggest that TL1A/DR3 pathway plays an important role in the augmentation of cytokine-induced IFN-gamma production in T cells and that DR3 expression is differentially regulated by IL-12/IL-18 in T cells and NK cells.

Diesel exhaust particles suppress in vivo IFN-gamma production by inhibiting cytokine effects on NK and NKT cells

Diesel exhaust particles (DEP) have strong, selective Th2 adjuvant activity when inhaled with conventional Ags. We used a novel technique for measuring in vivo cytokine production to investigate possible mechanisms by which DEP might promote a Th2 response. Injection of DEP i.p. stimulated IL-6 secretion, but failed to increase IL-4, IL-10, or TNF-alpha secretion, and decreased basal levels of IFN-gamma. When injected with or before LPS, DEP had little effect on the LPS-induced TNF-alpha responses, but partially inhibited the LPS-induced IL-10 response and strongly inhibited the LPS-induced IFN-gamma response. DEP also inhibited the IFN-gamma responses to IL-12, IL-12 plus IL-18, IL-2, and poly(I.C). DEP treatment had little effect on the percentages of NK and NKT cells in the spleen, but inhibited LPS-induced IFN-gamma production by splenic NK and NKT cells. In contrast, DEP failed to inhibit the IFN-gamma response by anti-CD3 mAb-activated NKT cells. Taken together, these observations suggest that DEP inhibit Toll-like receptor ligand-induced IFN-gamma responses by interfering with cytokine signaling pathways that stimulate NK and NKT cells to produce IFN-gamma. Our observations also suggest that DEP may promote a Th2 response by stimulating production of inflammatory cytokines while simultaneously inhibiting production of IFN-gamma, and raise the possibility that the same mechanisms contribute to the association between DEP exposure and asthma.

Murine hepatocyte cell lines promote expansion and differentiation of NK cells from stem cell precursors

While fetal liver is a major hematopoietic organ, normal adult liver provides a suitable microenvironment for a variety of immune cells and, in several pathological conditions, may become a site of extramedullary hematopoiesis. The direct influence of hepatocytes on hematopoietic cell differentiation is poorly understood. We have previously reported that the Met murine hepatocyte (MMH) untransformed hepatocytic lines retain several morphological and functional features of hepatocytes in vivo and are able to support the survival, self-renewal, and differentiation of hematopoietic precursors in a cell-cell contact system. Here we report the effects of soluble factors released by MMH lines on bone marrow-derived cells. Lymphohematopoietic cells were cultured in two different cell contact-free systems: transwell inserts on MMH feeder layers, and MMH conditioned medium (MMH-CM). Both culture systems were able to promote a substantial expansion of bone marrow-derived cells and their differentiation to natural killer (NK) cells that express the NK1.1 and U5A2-13 markers. Purified hematopoietic stem cells (Sca-1+Lin-), either plated as a bulk population or as single cells, were also able to differentiate into NK cells, when cultured in MMH-CM; thus, soluble factors secreted by MMH lines promote the expansion and differentiation of NK precursor cells. MMH-CM-derived NK cells are functionally active; stimulation by interleukin (IL)-12 together with IL-18 was required to induce interferon-gamma (IFNgamma) expression and to enhance their cytotoxic activity. In conclusion, our findings may imply a direct role of hepatocytes in NK cell development, and the system we have used may provide a tool for studying the molecular mechanisms of NK cell differentiation.

In vitro responsiveness to IL-18 in combination with IL-12 or IL-2 by PBMC from patients with bronchial asthma and atopic dermatitis

Interleukin (IL)-18 is a proinflammatory cytokine and is now recognized as an important regulator of both helper T cells (Th) 1 and 2 cytokine production. An increased IL-18 secretion has been reported in patients with allergic disorders. It is predominantly produced by activated macrophages, and synergizes with IL-12 and IL-2 to induce IFN-gamma synthesis, thereby promoting Th1 cytokine response. Paradoxically, IL-18, by itself, strongly induces immunoglobulin (Ig) E and allergic inflammation, indicating a role for IL-18 in promoting Th2 response. We investigated the inducing effect in vitro of combining IL-18 and Il-12 or Il-2 on Th1- and Th2-type cytokines production by peripheral blood mononuclear cells (PBMC) from patients with allergic diseases. PBMC derived from 44 allergic patients [23 bronchial asthma (BA) and 21 atopic dermatitis (AD)] and 20 healthy controls were cultured with IL-18 in the presence of phytohemagglutinin (PHA) and IL-12 or IL-2. The levels of IFN-gamma, IL-13, and IL-4 in the culture supernatants were measured using enzymatic immunoassaying. IFN-gamma production was detected in all cultures from nonallergic controls stimulated with IL-18 in the presence of IL-12; however, the results for five BA patients and five AD patients were under the detection limit for IFN-gamma. In collaboration with IL-2, IL-18 was able to induce IFN-gamma production by PBMCs from all nonallergic controls and all allergic patients, with the exception of one AD patient. Synergistic induction of IL-13 production was found in cultures with IL-18 + IL-2, and the IL-13 induction was significantly increased in BA patients when compared with that in nonallergic controls (P = 0.006). The stimulation by IL-18, even in combination with IL-2, failed to induce IL-4 production by PBMC from both nonallergic controls and allergic patients. Although the induction of IFN-gamma by IL-18 + IL-12 was impaired in around a quarter of the allergic patients, the impairment of the IFN-gamma production was completely restored by IL-2 in the presence of IL-18. Thus, IL-18 enhances IFN-gamma production through an IL-12-dependent pathway and exhibits synergism when combined with IL-2 in terms of enhanced IL-13 and IFN-gamma production, suggesting the involvement of IL-18/IL-12/IL-2 pathway in modulating Th1/Th2 cytokine response.

Aging of innate immunity: functional comparisons of NK/LAK cells obtained from bulk cultures of young and aged mouse spleen cells in high concentrations of interleukin-2

The technique of bulk cultivation of aged mouse spleen cells in high concentration of IL-2 was employed to obtain NK/LAK cells in sufficient number and enrichment for studies on the effects of aging on their functions. The yield and enrichment were equivalent to that of young mouse spleen cells. The aged and young mouse NK/LAK cells were equivalent also in their functional competence to proliferate, kill target cells and produce IFNgamma; i.e. they did not display age-associated defects typical of freshly-isolated NK/LAK cells. In two respects, however, the NK/LAK cells derived from aged mouse spleen were altered: (a) in the efficiency of nuclear translocation of transcription factors STAT 5A and 5B, and (b) in the deficiency in production of mRNA transcripts representing several chemokines. We recommend caution in the use of bulk cultivation in IL-2 to obtain NK/LAK cells for studies on aging. However, it does appear from this study that aging may severely affect chemokine production, at least in the case of NK/LAK cells.

Serum interleukin-12 and interleukin-18 levels as a tumor marker in patients with esophageal carcinoma

Interleukin (IL)-12 and IL-18 participate in tumor immunology. Serum IL-12 and IL-18 levels were determined in patients with esophageal carcinoma, and the relationship between clinicopathologic factors and prognosis was investigated. Peripheral blood samples were obtained from 15 healthy volunteers and from 70 patients with esophageal carcinoma before curative surgery. IL-12 and IL-18 levels were determined in each serum sample by enzyme-linked immunosorbent assay. Mean serum IL-12 and IL-18 levels were significantly higher in patients with esophageal carcinoma compared with healthy volunteers (P < 0.05) and mean serum IL-12 and IL-18 levels increased in patients as the pathologic stage progressed. A positive correlation was observed between serum IL-12 and IL-18 levels (P < 0.01). In patients with esophageal carcinoma, increasing serum IL-12 and IL-18 levels correlated with tumor growth and progression. The function of these two interleukin in the host immune response remains unclear. However, this part of the host immune response did not appear to contribute to the postoperative prognosis. Serum IL-12 and IL-18 levels might correlate with a certain depth of invasion and might be useful tumor markers in patients with esophageal carcinoma.

Determinants of Antileukemia Effects of Allogeneic NK Cells

In HLA-nonidentical bone marrow transplantation, we studied the characteristics of donor NK cells, recipient leukemia cells, and the cytokine environment that predict the antileukemia effects of allogeneic NK cells. We found that the risk of relapse in pediatric patients with hematologic malignancies was best predicted by a model taking into consideration the presence of inhibitory killer cell Ig-like receptors (KIRs) on the donor's NK cells and the absence of corresponding KIR ligand in the recipient's HLA repertoire (a receptor-ligand model). The risk of relapse was prognosticated less precisely by the Perugia donor-recipient KIR ligand-ligand mismatch model or by a natural cytotoxicity model. In contrast to the ligand-ligand model, we found that the new receptor-ligand model was accurate when analysis was applied to patients with lymphoid malignancy. These findings corroborate our observations that the recipient's KIR repertoire, which was derived from highly purified, HLA-disparate CD34+ cells, resumed a donor-specific pattern within 3 mo of transplantation, but did not correlate evidently with the donor or recipient ligand repertoire. In an in vitro assay and an in vivo mouse model, human NK cell cytotoxicity toward human leukemia cells with 11q23 chromosomal rearrangement increased with the number of receptor-ligand mismatch pairs or prestimulation with IL-12 and IL-18. These findings provide new insights into the determinants of antileukemia effects of allogeneic NK cells and therapeutic strategies.

Natural killer cells do not mediate facial motoneuron survival after facial nerve transection

The goal of the current study was to determine if natural killer (NK) cells mediate facial motoneuron (FMN) survival following injury. Wild-type (WT), perforin/recombinase activating gene-2 knockout (pfp/RAG-2 KO), and common gamma-chain (gammac)/RAG-2 KO mice received a right facial nerve axotomy. In WT mice, FMN survival was 86+/-1.0% relative to the contralateral control side. In contrast, pfp/RAG-2 and gammac/RAG-2 KO mice exhibited significant decreases in FMN survival ( approximately 20% and approximately 30%, respectively), relative to WT. Reconstitution of pfp/RAG-2 and gammac/RAG-2 KO mice with normal NK cells alone, failed to restore FMN survival levels to those of WT, but did restore functional lytic activity against YAC-1 cells. Reconstitution of pfp/RAG-2 and gammac/RAG-2 KO mice with splenocytes, and pfp/RAG-2 KO mice with CD4+ T-lymphocytes alone or in combination with NK cells, restored FMN survival levels to those of WT. Thus, NK cells appear to not be a component of immune cell-mediated rescue of motoneurons from axotomy induced cell death.

IL-15 and IL-2 oppositely regulate expression of the chemokine receptor CX3CR1

The chemokine receptor CX3CR1 (CX3C chemokine receptor 1) is expressed in mouse blood on natural killer (NK) cells and on monocytes. Because interleukin-15 (IL-15) is an essential cytokine for NK cell development and maintenance, we hypothesized that it may induce CX3CR1 expression on this cell type. In contrast, we found that in primary mouse bone marrow-derived NK cells IL-15 specifically inhibited CX3CR1 protein and mRNA accumulation, whereas the related cytokine IL-2 did not inhibit but instead increased CX3CR1 expression. Consistent with this finding, intravenous injection of a single dose of recombinant IL-15 into C57BL/6 mice decreased steady-state CX3CR1 levels 24 hours after injection in freshly isolated peripheral blood mononuclear cells (PBMCs), splenocytes, and bone marrow cells, and treatment of mouse PBMCs with IL-15 in vitro inhibited CX3CL1 (ligand for CX3CR1)-induced chemotaxis. These data suggest that IL-15 may be a negative regulator of innate immunity by inhibiting CX3CR1 expression. These data also suggest that IL-15 inhibition of CX3CR1 may subvert potential cell immunotherapy strategies in which IL-15 is used to expand NK cell populations in vivo or ex vivo. Finally, our results provide additional evidence for differential signaling by IL-2 and IL-15, despite usage of common beta gamma c receptor chains.

Innate immunity in the liver

PURPOSE OF REVIEW

The liver is constantly exposed to large varieties of antigens that are derived from the gastrointestinal tract, including dietary antigens, pathogens, and toxins. Its function as a major immune organ is now being appreciated. The liver lymphocyte population is enriched in macrophages (ie, Kupffer cells), natural killer and natural killer T cells, which constitute the innate immune system. This review will focus on recent advances in the understanding of mechanisms that regulate the hepatic innate immune system because the innate immune system may mediate many chronic liver diseases, including nonalcoholic fatty liver disease, and nonalcoholic steatohepatitis.

RECENT FINDINGS

Hepatic natural killer T cells modulate liver injury by balancing local production of proinflammatory (Th-1) and antiinflammatory (Th-2) cytokines. Hepatic natural killer T cell depletion leads to Th-1 polarization of hepatic cytokine production, increasing tumor necrosis factor alpha and interferon gamma. This potentates lipopolysaccharide-induced hepatotoxicity. The hepatic natural killer T cells themselves are regulated by Kupffer-cell-produced cytokines, dietary factors, and certain neurotransmitters, such as norepinephrine. In leptin-deficient ob/ob mice, an animal model for nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, insufficient norepinephrine increases hepatic natural killer T cell apoptosis, depleting hepatic natural killer T cells and inducing proinflammatory cytokine polarization. This contributes to chronic inflammation, increased lipopolysaccharide-induced hepatotoxicity, and insulin resistance in ob/ob mice.

SUMMARY

Assuming that defects in the hepatic innate immune system that promote Th-1 cytokine polarization are common pathogenic mechanisms for hepatic insulin resistance and nonalcoholic steatohepatitis, therapies that inhibit inflammatory activity may be beneficial for these disorders.

In vivo antitumor activity of NKT cells activated by the combination of IL-12 and IL-18

Interleukin-12 and IL-18 have been demonstrated to potentiate innate immunity in a variety of experimental tumor models, but the functional roles of NK and/or NKT cells and their mechanism of action in these models have not been fully addressed. Through adoptive transfer of NKT cells activated in vitro with a combination of IL-12 plus IL-18 (IL-12/IL-18 NKT) into syngeneic animals, we demonstrate in this study that IL-12/IL-18 NKT cells are essential and collaborate with the host's own NK cells in natural host immunity against the growth of ALC and MC57X syngeneic tumors. The relative roles of the adoptively transferred IL-12/IL-18 NKT cells and endogenous NK cells in host protection were first shown in normal C57BL/6 (B6) mice treated with anti-asialo GM1 Ab that selectively depletes NK cells; second, in B6.TCRJalpha281(-/-) mice specifically deficient for NKT cells; and third, in B6.scid mice that also lack NKT cells. Furthermore, by injecting normal B6 mice with anti-IL-2 and/or anti-IFN-gamma mAb, we could demonstrate that effective innate immunity against both types of syngeneic tumors was dependent on the production of IL-2 and IFN-gamma by the adoptively transferred NKT cells. In vitro studies confirmed both the secretion of IL-2 and IFN-gamma by the IL-12/IL-18-activated NKT cells and their collaborative role with NK cells for lysis of ALC and MC57X syngeneic tumor targets. This is the first description of an antitumor function of IL-12/IL-18 NKT cells adoptively transferred into syngeneic hosts that provides the basis for a new modality in the cellular immunotherapy of cancer.

Natural killer cell cytolytic activity is necessary for in vivo antitumor activity of the dipeptide L-glutamyl-L-tryptophan

A dipeptide, L-glutamyl L-tryptophan (L-glu-L-trp), was identified in a screen for immunomodulators in the soluble fraction of the thymus. L-glu-L-trp inhibits tumor growth in mice without showing direct cellular toxicity in a variety of human tumor cell lines. L-glu-L-trp antitumor activity in vivo requires the presence of natural killer (NK) cells. Defective trafficking of cytoplasmic granules caused by the Lyst mutation also resulted in loss of antitumor activity of the dipeptide. The effect of L-glu-L-trp on tumor growth in mice with targeted gene mutations demonstrated the absolute requirement for perforin for antitumor activity. The requirement of 2 major modulators of NK cell activity, gamma interferon (IFNgamma) and interleukin (IL)-12, were also tested. L-glu-L-trp had full antitumor activity in IFNgamma knockout mice, but had significantly diminished activity in IL-12 knockout mice. These data show that L-glu-L-trp antitumor activity in mice is dependent on cytolytic cell activity of NK or NKT cells. L-glu-L-trp in vivo regulates NK cell function independent of IFNgamma but partly dependent on IL-12.

Interleukin-12 and interleukin-2-induced invariant natural killer T-cell cytokine secretion and perforin expression independent of T-cell receptor activation

Human invariant natural killer (iNK) T cells expressing an invariant Valpha24-Jalpha15 T-cell receptor (TCR) are thought to be important regulators of autoimmunity and tumour surveillance. Two major subsets of iNK T cells, CD4+ or CD4- CD8- are known to exist, but the in vivo importance of CD4 expression is unclear. Since interleukin-12 (IL-12) is a key iNK T-cell-activating cytokine, the effect of IL-12 plus or minus the T-cell growth factor IL-2 on a large panel of CD4+ versus CD4- CD8- iNK T-cell clones was examined. Strikingly, IL-12 and IL-2 significantly activated iNK T cells to secrete IL-4, interferon-gamma and granulocyte-macrophage colony-stimulating factor, and up-regulated perforin expression in the absence of TCR stimulation. Furthermore, IL-2 and IL-12 treatment resulted in a preferential increase in apoptosis of CD4- CD8- clones. Thus, independent of TCR activation, IL-2 and IL-12 can directly activate iNK T cells and provide a selective advantage to the CD4+ iNK T-cell population.

Analysis of cytokine regulators inducing interferon production by mouse uterine natural killer cells

In mice and women, terminal differentiation of uterine natural killer (uNK) cells commences during endometrial decidualization. Both proliferation and interferon (IFN)-gamma are induced. Uterine NK cell precursors appear to home from secondary lymphoid organs to decidualizing uteri and localize mesometrially to the central decidua basalis, the site of maternal arterial modification at Gestation Days (gd) 9.5-10. In mice, genetic absence of uNK cells results in absence of pregnancy-induced spiral artery modification. Administration of IFN-gamma to uNK-negative pregnant females induces arterial modifications without fetal loss. In this study, we investigated the roles of cytokines, known in other tissues to differentiate and activate NK cells, in induction of IFN-gamma production in normal mouse implantation sites. Fecundity evaluation, implantation site morphometry, and IFN-gamma quantification in interleukin (IL)-12p40(0/0), IL-18(0/0), dual IL-12p40(0/0)/IL-18(0/0) and congenic strains revealed the importance of both IL-12 and IL-18 in the induction of spiral artery modification and IFN-gamma synthesis. Immediately after implantation, IL-18 was localized transiently to decidual cells, but by gd8, IL-18 was produced solely by uNK cells, suggesting that early uNK cells are activated by stroma and lymphocyte-derived signals maintain later uNK cell activation. Mesometrial tissue of C57Bl/6J mice was examined by reverse transcription polymerase chain reaction assay in virgin, early postimplantation, and midgestation females for expression of the heterodimeric cytokines IL-23 (composed of IL-12p40 and a novel alpha chain), IL-27 (composed of two IL-12-related chains) and IL-27R. No expression was detected in virgin uteri. The four genes were induced by gd6, and uNK cells isolated from midgestation transcribed IL-23alpha and IL-27R. This study advances the understanding of uNK cell activation during normal pregnancy.

IL-12 and IL-18 act in synergy to clear vaccinia virus infection: involvement of innate and adaptive components of the immune system

Development of a protective host response against intracellular pathogens requires innate and cell-mediated immune responses, with cytokines playing an important role in host defences. Different studies in mice have shown that IL-12 can promote protective immunity to a variety of viruses but, during virus infection, little is known about the in vivo function of IL-18 alone or in combination with IL-12. Using recombinant vaccinia viruses (rVVs) expressing IL-12 and IL-18, the antiviral role of both cytokines in mice has been analysed. The specific anti-VV immune response elicited and the persistence of the virus in target tissues were compared in BALB/c mice inoculated with rVVs expressing IL-12 and IL-18 either singly or in combination. Delivery of IL-12 and IL-18 by rVVs in mice induced a significant enhancement in virus clearance from ovaries and spleen, greater than that expected from the sum of action of both cytokines. Virus clearance involved NK and T cells, as demonstrated in mice depleted of NK cells and in immunodeficient SCID animals. Th1 parameters (CD8(+) T cell response and IgG2a : IgG1 ratios) were increased in mice inoculated with rVVs expressing both IL-12 and IL-18 as compared to those animals receiving a single cytokine. These findings indicate that when IL-12 and IL-18 are delivered by rVVs, different mechanisms involving both the innate and specific arms of the immune system act as mediators in the synergistic action of IL-12 and IL-18, leading to VV clearance. These results are of interest for the design of prophylactic as well as therapeutic VV-based strategies.

Disparate functions of immature and mature human myeloid dendritic cells: implications for dendritic cell-based vaccines

Although antigen-loaded dendritic cells (DC) are being investigated as antitumor vaccines, which DC differentiation state is most effective is not clear. Three DC functions that may be critical for immunization potential are expression of CD80/86, cytokine production following CD40 engagement, and migration to chemokine receptor 7-binding chemokines. We therefore examined highly purified human monocyte-derived immature and mature DC for these properties from normal donors and cancer patients. Although high expression of CD80/86 and migration to 6Ckine + macrophage-inflammatory protein-3beta were properties of mature DC, cytokine production following CD40 ligation was superior by immature DC. Loss of cytokine secretion occurred with multiple maturation conditions, was not apparently reversible, and was also seen with lipopolysaccharide stimulation in correlation with down-regulated Toll-like receptor expression. Our results suggest that the functions thought to contribute to optimal T cell priming are not coexpressed by the same DC population and that immature and mature DC likely possess distinct CD40-mediated signaling events.

NK cells regulate CD4 responses prior to antigen encounter

NK cells not only respond rapidly to infection, shaping subsequent adaptive immunity, but also play a role in regulating autoimmune disease. The ability of NK cells to influence adaptive immunity before Ag exposure was examined in a gender-dependent model of preferential Th1 and Th2 activation. The inability of young adult male SJL mice to activate Th1 cells was reversed via depletion of NK1.1(+) cells, whereas the presence or the absence of NK1.1(+) cells did not alter responses in age-matched females. Consistent with a gender-dependent role in regulating adaptive immunity, significantly more NK1.1(+) cells were present in males compared with females, and this difference was reversed by castration. In contrast to NK1.1(+) cells derived from C57BL/6 mice, no spontaneous cytokine secretion was detected in NK1.1(+) cells derived from either male or female SJL mice, although an increased frequency of IL-10-secreting NK1.1(+) cells was observed in males vs females following in vitro stimulation. Direct evidence that NK1.1(+) cells in males influence CD4(+) T cell activation before Ag exposure was demonstrated via the adoptive transfer of APC from control and NK1.1-depleted males. The absence of a functional NK T cell population in SJL mice suggests that NK cells influence adaptive immunity before Ag exposure via alterations in APC activity.

IL-21 in synergy with IL-15 or IL-18 enhances IFN-gamma production in human NK and T cells

NK and T cell-derived IFN-gamma is a key cytokine that stimulates innate immune responses and directs adaptive T cell response toward Th1 type. IL-15, IL-18, and IL-21 have significant roles as activators of NK and T cell functions. We have previously shown that IL-15 and IL-21 induce the expression of IFN-gamma, T-bet, IL-12R beta 2, and IL-18R genes both in NK and T cells. Now we have studied the effect of IL-15, IL-18, and IL-21 on IFN-gamma gene expression in more detail in human NK and T cells. IL-15 clearly activated IFN-gamma mRNA expression and protein production in both cell types. IL-18 and IL-21 enhanced IL-15-induced IFN-gamma gene expression. IL-18 or IL-21 alone induced a modest expression of the IFN-gamma gene but a combination of IL-21 and IL-18 efficiently up-regulated IFN-gamma production. We also show that IL-15 activated the binding of STAT1, STAT3, STAT4, and STAT5 to the regulatory sites of the IFN-gamma gene. Similarly, IL-21 induced the binding of STAT1, STAT3, and STAT4 to these elements. IL-15- and IL-21-induced STAT1 and STAT4 activation was verified by immunoprecipitation with anti-phosphotyrosine Abs followed by Western blotting with anti-STAT1 and anti-STAT4 Abs. IL-18 was not able to induce the binding of STATs to IFN-gamma gene regulatory sites. IL-18, however, activated the binding of NF-kappa B to the IFN-gamma promoter NF-kappa B site. Our results suggest that both IL-15 and IL-21 have an important role in activating the NK cell-associated innate immune response.

What does it take to make a natural killer?

We know how B and T cells develop, what they 'see' and the receptors they 'see with'. By contrast, and despite an unprecedented increase in the number of receptors and ligands known to regulate the activity of natural killer (NK) cells, we still have many questions regarding how these cells develop. Nevertheless, we are beginning to understand the transcriptional programmes of NK-cell maturation and the role of the effector functions of NK cells in the regulation of immune responses. An improved knowledge of NK-cell development in mice and humans might be useful to harness the power of these natural killers in the clinic to fight autoimmune diseases, infection and cancer.

Transfer of TCR genes into mature T cells is accompanied by the maintenance of parental T cell avidity

The adoptive transfer of tumor-specific T cells expanded in vitro can be of significant therapeutic value in select cancer patients. This strategy is limited though, as it is often difficult, if not impossible, to obtain T cells of clinical value. The transfer of TCR genes to mature T cells to generate tumor-reactive T cells provides a potential mechanism to overcome these limitations. To evaluate the feasibility of such an approach and the quality of the resulting T cells, we generated replication-deficient retroviral vectors using the well-characterized OT-1 TCR genes. After transducing murine T cells, we were able to expand large numbers of Ag-specific T cells that were functionally active against tumor cells expressing the relevant Ag. Furthermore, we found that T cells expressing retrovirally encoded TCR had avidity that was similar to that of the parental clone. This maintenance of avidity was despite variable expression of the retrovirally encoded TCR and the presence of potentially competing endogenous TCRs. These results suggest that the inherent qualities of the TCR, as dictated by the coding sequence, are the most critical parameters in the generation of high-avidity T cells.

Murine leptin deficiency alters Kupffer cell production of cytokines that regulate the innate immune system

BACKGROUND & AIMS

ob/ob mice are used to study the mechanisms that regulate the progression from steatosis to nonalcoholic steatohepatitis. The livers of ob/ob mice are depleted of CD4-positive natural killer cells, components of the innate immune system that induce anti-inflammatory cytokines. Although this may explain the sensitivity of fatty livers to lipopolysaccharide, why such hepatic CD4-positive natural killer cell depletion occurs is uncertain. Because leptin regulates macrophages, our hypothesis is that leptin deficiency alters Kupffer cell production of cytokines that inhibit (e.g., interleukin [IL]-12) or enhance (e.g., IL-15) hepatic CD4-positive natural killer cell viability.

METHODS

Kupffer cell cytokine production and the hepatic content of CD4-positive natural killer cells were compared in ob/ob and lean mice. ob/ob mice were then treated with IL-15 or leptin to determine whether either factor improved their immunologic abnormalities.

RESULTS

Compared with control Kupffer cells, ob/ob Kupffer cells produced less IL-15 basally and more IL-12 after lipopolysaccharide stimulation. Treatment of ob/ob mice with IL-15 for 1 week normalizes their hepatic CD4-positive natural killer cell content. Leptin increases the hepatic expression of IL-15 in ob/ob mice and partially replenishes their hepatic CD4-positive natural killer cells.

CONCLUSIONS

Leptin deficiency increases hepatic IL-12 and reduces hepatic IL-15 expression. The abnormal production of these Kupffer cell factors promotes hepatic CD4-positive natural killer cell depletion in ob/ob livers.

IL-18 is present at the maternal-fetal interface and enhances cytotoxic activity of decidual lymphocytes

PROBLEM

Perforin expressing uterine natural killer (uNK) cells are under complex cytokine influence. The aim of the study was to investigate the presence and role of interleukin (IL)-18 on NK cytolytic potential at maternal-fetal (M-F) interface.

METHOD OF STUDY

Peripheral blood cells and decidual tissue were obtained from elective pregnancy termination of normal human 6-10-week-old pregnancies. Perforin expression and cytolytic activity of peripheral blood (PBL) and decidual lymphocytes (DL) were analyzed by flow cytometry. IL-18 positive decidual adherent cells (DAC) were detected by the same method. Interleukin-18 and IL-18 receptor (IL-18R) expression on the trophoblastic cells was detected by immunohistology using biotinylated anti-IL-18 and IL-18R monoclonal antibodies.

RESULTS

The IL-18 added in a dose of 10 ng/mL up-regulates perforin expression and cytolytic activity of DL. Simultaneous stimulation with IL-18 and IL-12 enhanced DL cytolytic activity, while IL-18 combined with IL-10 or IL-15 did not show this effect. Cytolytic activity of PBL was up-regulated by IL-18 as well, and this effect was enhanced by the addition of IL-12 and IL-15. Interleukin-18 did not affect perforin-protein expression in cultured PBL. Approximately 20% of DAC were IL-18 positive and these cells were mostly human leukocyte antigen (HLA)-DR negative. IL-18R positive cells were found on syncytiotrophoblast cell layer, interstitial tissue cells of villi and fetal blood cells. There was no detectable IL-18 staining on trophoblast cell layer on villi, but strong staining of fetal blood cells in villous vessels.

CONCLUSION

These are first results showing IL-18R expression, but not IL-18 expression on villous trophoblastic cells, as well as enhancement of perforin expression and NK cytolytic potential of DL under the influence of IL-18. IL-18 in concert with other cytokines and hormones could play an important role in the regulation of cytolytic potential of first trimester pregnancy decidual and peripheral blood NK cells.

Characterization of a murine NKT cell tumor previously described as an acute myelogenous leukemia

C1498 is an atypical myeloid leukemia that originated in a C57BL/6 mouse and has been used as a model for acute myelogenous leukemia. In studies of the immune response to C 1498, we found that this tumor contained mRNA encoding the canonical NKT cell receptor Vbeta8.2-Valpha14Jalpha281. Although cell-surface phenotypic analysis showed C1498 to be negative for NK1.1, it expressed several other molecules associated with NKT cell populations, such as DX5, CDld, CD69, CD44, CD45RB and B220. RT-PCR demonstrated that C1498 contained CD3epsilon mRNA transcripts, but message was not found for CD4, CD8alpha, or CD8beta. This indicates that C1498 falls within the double negative (CD4-CD8-) NKT cell lineage. RNase protection analysis showed that C1498 expressed mRNA for IL-2, IL-15, and macrophage migration inhibitory factor (MIF). These findings suggest that C1498 should be re-classified as a NKT cell leukemia with atypical myeloid features. It may, therefore, be a novel cell line in which to study NKT cell development and serve as a model for human NKT cell malignancies.

IL-2 and IL-12 alter NK cell responsiveness to IFN-gamma-inducible protein 10 by down-regulating CXCR3 expression

Cytokine treatment of NK cells results in alterations in multiple cellular responses that include cytotoxicity, cytokine production, proliferation, and chemotaxis. To understand the molecular mechanisms underlying these responses, microarray analysis was performed and the resulting gene expression patterns were compared between unstimulated, IL-2, IL-2 plus IL-12, and IL-2 plus IL-18-stimulated NK92 cells. RNase protection assays and RT-PCR confirmed microarray predictions for changes in mRNA expression for nine genes involved in cell cycle progression, signal transduction, transcriptional activation, and chemotaxis. Multiprobe RNase protection assay also detected changes in the expression of CCR2 mRNA, a gene that was not imprinted on the microarray. We subsequently expanded our search for other chemokine receptor genes absent from the microarray and found an IL-2- and IL-12-dependent decrease in CXCR3 receptor mRNA expression in NK92 cells. A detailed analysis of CXCR3 expression in primary NK cells revealed that an IL-2 and an IL-12 together significantly decreased the CXCR3 receptor mRNA and receptor surface expression by 6 and 24 h of treatment, respectively. This decrease in receptor expression was associated with a significant reduction in chemotaxis in the presence of IFN-gamma-inducible protein-10. The decline in CXCR3 mRNA was due to transcriptional and posttranscriptional mechanisms as the addition of actinomycin D to IL-2- and IL-12-treated NK92 slightly altered the half-life of the CXCR3 mRNA. Collectively, these data suggest that IL-2 and IL-12 directly affect NK cell migratory ability by rapid and direct down-regulation of chemokine receptor mRNA expression.

Formation of the killer Ig-like receptor repertoire on CD4+CD28null T cells

Killer Ig-like receptors (KIRs) are expressed on CD4(+)CD28(null) T cells, a highly oligoclonal subset of T cells that is expanded in patients with rheumatoid arthritis. It is unclear at what stage of development these T cells acquire KIR expression. To determine whether KIR expression is a consequence of clonal expansion and replicative senescence, multiple CD4(+)CD28(null) T cell clones expressing the in vivo dominant TCR beta-chain sequences were identified in three patients and analyzed for their KIR gene expression pattern. Based on sharing of TCR sequences, the clones were grouped into five clone families. The repertoire of KIRs was diverse, even within each clone family; however, the gene expression was not random. Three particular receptors, KIR2DS2, KIR2DL2, and KIR3DL2, had significant differences in gene expression frequencies between the clone families. These data suggest that KIRs are successively acquired after TCR rearrangement, with each clone family developing a dominant expression pattern. The patterns did not segregate with the individual from whom the clones were derived, indicating that peripheral selection in the host environment was not a major shaping force. Several models were examined using a computer algorithm that was designed to simulate the expression of KIRs at various times during T cell proliferation. The computer simulations favored a model in which KIR gene expression is inducible for a limited time during the initial stages of clonal expansion.

Hepatic injury induced by interleukin-18 administration: importance of preceding priming effect

The priming effects of obstructive jaundice by bile duct ligation on interleukin (IL)-18-induced hepatic injury are investigated. The production of IL-12 and tumor necrosis factor-alpha increased 3 days after bile duct ligation. Subsequent IL-18 injection to rats with obstructive jaundice caused by BDL resulted in prominent interferon-gamma production and hepatic injury. These results suggest that IL-18 with IL-12 and/or tumor necrosis factor-alpha have synergistic effects on the induction of hepatic injury via interferon-gamma production on this model.

Natural killer T (NKT) cells and their role in antitumor immunity

Natural killer T (NKT) cells have become a major focus for those who study the innate immune response to tumors and infectious diseases, as well as autoimmunity. These novel T lymphocytes produce both Th1 and Th2 cytokines, recognize phospholipid and glycolipid antigens presented by CD1 molecules in a similar manner as peptides are recognized by cytotoxic T lymphocytes (CTL), and kill tumor cell targets by a perforin-dependent mechanism like NK cells and CTL. These ascribed functions thus demonstrate that NKT cells are a unique cytotoxic effector cell subpopulation with a kaleidoscope of activities. Because they can mediate antitumor effects in vivo with or without the collaboration of NK cells, the study of NKT cells in antitumor immunity may lead to novel treatments based on the ability to manipulate the generation and/or activity of these multifunctional lymphocytes.