In‐vivo stimulation of macaque natural killer T cells with α‐galactosylceramide

Natural killer T cells are a potent mediator of anti‐viral immunity in mice, but little is known about the effects of manipulating NKT cells in non‐human primates. We evaluated the delivery of the NKT cell ligand, α‐galactosylceramide (α‐GalCer), in 27 macaques by studying the effects of different dosing (1–100 μg), and delivery modes [directly intravenously (i.v.) or pulsed onto blood or peripheral blood mononuclear cells]. We found that peripheral NKT cells were depleted transiently from the periphery following α‐GalCer administration across all delivery modes, particularly in doses of ≥10 μg. Furthermore, NKT cell numbers frequently remained depressed at i.v. α‐GalCer doses of >10 μg. Levels of cytokine expression were also not enhanced after α‐GalCer delivery to macaques. To evaluate the effects of α‐GalCer administration on anti‐viral immunity, we administered α‐GalCer either together with live attenuated influenza virus infection or prior to simian immunodeficiency virus (SIV) infection of two macaques. There was no clear enhancement of influenza‐specific T or B cell immunity following α‐GalCer delivery. Further, there was no modulation of pathogenic SIV_mac251 infection following α‐GalCer delivery to a further two macaques in a pilot study. Accordingly, although macaque peripheral NKT cells are modulated by α‐GalCer in vivo, at least for the dosing regimens tested in this study, this does not appear to have a significant impact on anti‐viral immunity in macaque models.     

Presentation of alpha-galactosylceramide by murine CD1d to natural killer T cells is facilitated by plasma membrane glycolipid rafts

CD1 molecules are non-polymorphic major histocompatibility complex class I-related proteins that bind and present glycolipid antigens to T-cell antigen receptors (TCR) expressed by alphabeta T cells or natural killer-like T cells (NKT). Anti-metastatic properties of NKT cells reactive to the CD1d-binding antigen alpha-galactosylceramide (alpha-GalCer) are now being explored as a contributor to tumour cell killing. In this study, we tested the hypothesis that presentation of alpha-GalCer by murine CD1d (mCD1d) to mCD1d-restricted NKT cells was facilitated by plasma membrane glycolipid rafts. Confocal microscopy of mCD1d-transfected A20 B cells (A20mCD1d) demonstrated that mCD1d was raft-localized. This observation was confirmed by immunoblotting of raft fractions isolated on sucrose density gradients. Raft disruption by the cholesterol-binding agent nystatin, or short-chain ceramides, inhibited presentation of low concentrations of alpha-GalCer to NKT cells. Inhibition of antigen presentation was reversed by treatment of A20mCD1d cells with higher alpha-GalCer concentrations, or removal of raft-disrupting agents. These data indicate that partitioning of mCD1d into membrane rafts increases the capacity of antigen-presenting cells to present limiting quantities of glycolipid antigens, perhaps by stabilizing mCD1d/antigen structures on the plasma membrane and optimizing TCR engagement on NKT cells.     

Invariant natural killer T (iNKT) cell exhaustion in sarcoidosis

Invariant natural killer T (iNKT) cells are integral components of immune responses during many chronic diseases, yet their surface phenotypes, subset distribution, and polyfunctional capacity in this environment are largely unknown. Therefore, using flow cytometry, we determined iNKT cell phenotypic and functional characteristics in subjects with chronic inflammatory disease sarcoidosis and matched controls. We found that sarcoidosis subjects displayed lower iNKT‐cell frequencies, which correlated with lung fibrosis, C‐reactive protein levels, and other measures of clinical disease. The CD4^?CD8^? (double negative, DN) iNKT‐cell population was selectively lower in diseased individuals and the remaining DN iNKT cells exhibited higher frequencies of the activation markers CD69 and CD56. Functionally, both total IFN‐γ⁺ and the dual‐functional IFN‐γ⁺ TNF‐α⁺ iNKT cells were decreased in sarcoidosis subjects and these functional defects correlated with total iNKT‐cell circulating frequencies. As the loss of polyfunctionality can reflect functional exhaustion, we measured the surface antigens programmed death‐1 receptor and CD57 and found that levels inversely correlated with dual‐functional iNKT‐cell percentages. These findings reveal that, similar to traditional T cells, iNKT cells may also undergo functional exhaustion, and that circulating iNKT‐cell frequencies reflect these defects. Programmed death‐1 receptor antagonists may therefore be attractive therapeutic candidates for sarcoidosis and other iNKT‐cell‐mediated chronic diseases.     

α‐GalCer ameliorates listeriosis by accelerating infiltration of Gr‐1+ cells into the liver

α‐Galactosylceramide (α‐GalCer) activates invariant (i)NKT cells, which in turn stimulate immunocompetent cells. Although activation of iNKT cells appears critical for regulation of immune responses, it remains elusive whether protection against intracellular bacteria can be induced by α‐GalCer. Here, we show that α‐GalCer treatment ameliorates murine listeriosis, and inhibits inflammation following Listeria monocytogenes infection. Liver infiltration of Gr‐1⁺ cells and γ/δ T cells was accelerated by α‐GalCer treatment. Gr‐1⁺ cell and γ/δ T‐cell depletion exacerbated listeriosis in α‐GalCer‐treated mice, and this effect was more pronounced after depletion of Gr‐1⁺ cells than that of γ/δ T cells. Although GM‐CSF and IL‐17 were secreted by NKT cells after α‐GalCer treatment, liver infiltration of Gr‐1⁺ cells was not prevented by neutralizing mAb. In parallel to the numerical increase of CD11b⁺Gr‐1⁺ cells in the liver following α‐GalCer treatment, CD11b^?Gr‐1⁺ cells were numerically reduced in the bone marrow. In addition, respiratory burst in Gr‐1⁺ cells was enhanced by α‐GalCer treatment. Our results indicate that α‐GalCer‐induced antibacterial immunity is caused, in part, by accelerated infiltration of Gr‐1⁺ cells and to a lesser degree of γ/δ T cells into the liver. We also suggest that the infiltration of Gr‐1⁺ cells is caused by an accelerated supply from the bone marrow.     

In vivo activation of invariant V alpha 14 natural killer T cells by alpha-galactosylceramide sequentially induces Fas-dependent and -independent cytotoxicity

The present study was designed to clarify the cytotoxic capacities of invariant V alpha 14 natural killer T (iNKT) cells activated in vivo. We found that as early as 2 h after a single injection of alpha-galactosylceramide (alpha-GalCer), sorted iNKT splenocytes from treated mice kill Fas-transfected target cells. The implication of the Fas pathway in this lysis was strengthened by both the blockage of cytotoxicity in the presence of anti-Fas ligand (FasL) monoclonal antibody (mAb) and the up-regulation of FasL expression on iNKT cells. Sorted NK cells did not participate in the lytic activity at this time point. Yet, they became cytotoxic later on, 24 h post-treatment, when target cell lysis was mainly independent of the Fas pathway. This type of cell killing was predominant at this later time point, even though iNKT cells conserved a slight Fas-dependent cytotoxicity. NK cells failed to acquire the ability to kill target cells when IFN-gamma production in alpha-GalCer-injected mice was blocked by anti-IFN-gamma mAb, underscoring the major role of this cytokine. In conclusion, our findings provide the first direct evidence that iNKT cells can exert Fas-dependent cytotoxicity very shortly after in vivo alpha-GalCer activation and later, through IFN-gamma secretion, enable NK cells to kill target cells in a Fas-independent pathway.     

Activation of invariant natural killer T cells in regional lymph nodes as new antigen‐specific immunotherapy via induction of interleukin‐21 and interferon‐γ

Invariant natural killer T (iNKT) cells play important immunoregulatory functions in allergen‐induced airway hyperresponsiveness and inflammation. To clarify the role of iNKT cells in allergic rhinitis (AR), we generated bone marrow‐derived dendritic cells (BMDCs), which were pulsed by ovalbumin (OVA) and α‐galactosylceramide (OVA/α‐GalCer‐BMDCs) and administered into the oral submucosa of OVA‐sensitized mice before nasal challenge. Nasal symptoms, level of OVA‐specific immunoglobulin (IgE), and T helper type 2 (Th2) cytokine production in cervical lymph nodes (CLNs) were significantly ameliorated in wild‐type (WT) mice treated with OVA/α‐GalCer‐BMDCs, but not in WT mice treated with OVA‐BMDCs. These anti‐allergic effects were not observed in Jα18^–/– recipients that lack iNKT cells, even after similar treatment with OVA/α‐GalCer‐BMDCs in an adoptive transfer study with CD4⁺ T cells and B cells from OVA‐sensitized WT mice. In WT recipients of OVA/α‐GalCer‐BMDCs, the number of interleukin (IL)‐21‐producing iNKT cells increased significantly and the Th1/Th2 balance shifted towards the Th1 dominant state. Treatment with anti‐IL‐21 and anti‐interferon (IFN)‐γ antibodies abrogated these anti‐allergic effects in mice treated with α‐GalCer/OVA‐BMDCs. These results suggest that activation of iNKT cells in regional lymph nodes induces anti‐allergic effects through production of IL‐21 or IFN‐γ, and that these effects are enhanced by simultaneous stimulation with antigen. Thus, iNKT cells might be a useful target in development of new treatment strategies for AR.     

Invariant natural killer T cells in lupus patients promote IgG and IgG autoantibody production

IgG autoantibodies, including antibodies to double‐stranded DNA (dsDNA), are pathogenic in systemic lupus erythematosus (SLE), but the mechanisms controlling their production are not understood. To assess the role of invariant natural killer T (iNKT) cells in this process, we studied 44 lupus patients. We took advantage of the propensity of PBMCs from patients with active disease to spontaneously secrete IgG in vitro. Despite the rarity of iNKT cells in lupus blood (0.002–0.05% of CD3‐positive T cells), antibody blockade of the conserved iNKT TCR or its ligand, CD1d, or selective depletion of iNKT cells, inhibited spontaneous secretion of total IgG and anti‐dsDNA IgG by lupus PBMCs. Addition of anti‐iNKT or anti‐CD1d antibody to PBMC cultures also reduced the frequency of plasma cells, suggesting that lupus iNKT cells induce B‐cell maturation. Like fresh iNKT cells, expanded iNKT‐cell lines from lupus patients, but not healthy subjects, induced autologous B cells to secrete antibodies, including IgG anti‐dsDNA. This activity was inhibited by anti‐CD40L antibody, as well as anti‐CD1d antibody, confirming a role for CD40L‐CD40 and TCR‐CD1d interactions in lupus iNKT‐cell‐mediated help. These results reveal a critical role for iNKT cells in B‐cell maturation and autoantibody production in patients with lupus.     

Engagement of glycosylphosphatidylinositol-anchored proteins results in enhanced mouse and human invariant natural killer T cell responses

Invariant natural killer T (iNKT) cells are a small subset of lymphocytes that recognize glycolipid antigens in the context of CD1d and consequently produce large quantities of pro-inflammatory and/or anti-inflammatory cytokines. Several transmembrane glycoproteins have been implicated in the co-stimulation of iNKT cell responses. However, whether glycosylphosphatidylinositol (GPI)-anchored proteins can function in this capacity is not known. Here, we demonstrate that antibody-mediated cross-linking of the prototype mouse GPI-anchored protein Thy-1 (CD90) on the surface of a double-negative (CD4⁻CD8⁻) iNKT cell line leads to cytokine production at both the mRNA and protein levels. In addition, Thy-1 triggering enhanced cytokine secretion by iNKT cells that were concomitantly stimulated with α-galactosylceramide (αGC), consistent with a co-stimulatory role for Thy-1 in iNKT cell activation. This was also evident when a CD4⁺ mouse iNKT cell line or primary hepatic NKT cells were stimulated with αGC and/or anti-Thy-1 antibody. Cross-linking Ly-6A/E, another GPI-anchored protein, could also boost cytokine secretion by αGC-stimulated iNKT cells, suggesting that the observed effects reflect a general property of GPI-anchored proteins. To extend these results from mouse to human cells, we focused on CD55, a GPI-anchored protein that, unlike Thy-1, is expressed on human iNKT cells. Cross-linking CD55 augmented αGC-induced iNKT cell responses as judged by more vigorous proliferation and higher CD69 expression. Collectively, these findings demonstrate for the first time that GPI-anchored proteins are able to co-stimulate CD1d-restricted, glycolipid-reactive iNKT cells in both mice and humans.     

α‐Galactosylceramide‐activated murine NK1.1+ invariant‐NKT cells in the myometrium induce miscarriages in mice

Innate immunity, which is unable to discriminate self from allo‐antigens, is thought to be important players in the induction of miscarriages. Here, we show that the administration of IL‐12 to syngeneic‐mated C57BL/6 mice on gestation day 7.5 (Gd 7.5), drives significant miscarriages in pregnant females. Furthermore, the administration on Gd 7.5 of α‐galactosylceramide (α‐GalCer), which is known to activate invariant natural killer T (iNKT) cells, induced miscarriages in both syngeneic‐mated C57BL/6 mice and allogeneic‐mated mice (C57BL/6 (♀) × BALB/c (♂)). Surprisingly, the percentages of both DEC‐205⁺ DCs and CD1d‐restricted NK1.1⁺ iNKT cells were higher in the myometrium of pregnant mice treated i.p. with α‐GalCer than in the decidua. IL‐12 secreted from α‐GalCer‐activated DEC‐205⁺ DCs stimulated the secretion of cytokines, including IL‐2, IL‐4, IFN‐γ, TNF‐α, perforin, and granzyme B, from the NK1.1⁺ iNKT cells in the myometrium, leading to fetal loss in pregnant mice. Finally, the i.p. administration of IL‐12 and/or α‐GalCer in iNKT‐deficient Jα18(‐/‐) (Jα18 KO) mice did not induce miscarriages. This study provides a new perspective on the importance of the myometrium, rather than the decidua, in regulating pregnancy and a mechanism of miscarriage mediated by activated DEC‐205⁺ DCs and NK1.1⁺ iNKT cells in the myometrium of pregnant mice.     

Critical roles of conventional dendritic cells in promoting T cell‐dependent hepatitis through regulating natural killer T cells

Dendritic cells (DCs) play critical roles in initiating and regulating innate immunity as well as adaptive immune responses. However, the role of conventional dendritic cells (cDCs) in concanavalin A (ConA)‐induced fulminant hepatitis is unknown. In this study, we demonstrated that depletion of cDCs using either CD11c‐diphtheria toxin receptor transgenic mice (DTR Tg) mice or anti‐CD11c antibody reduced the severity of liver injury significantly, indicating a detrimental role of cDCs in ConA‐induced hepatitis. We elucidated further the pathological role of cDCs as being the critical source of interleukin (IL)‐12, which induced the secretion of interferon (IFN)‐γ by natural killer (NK) T cells. Reconstitution of cDCs‐depleted mice with IL‐12 restored ConA‐induced hepatitis significantly. Furthermore, we determined that NK T cells were the target of DC‐derived IL‐12, and NK T cells contributed to liver inflammation and injury through production of IFN‐γ. In summary, our study demonstrated a novel function of cDCs in mediating ConA‐induced hepatitis through regulating IFN‐γ secretion of NK T cells in an IL‐12‐dependent fashion. Targeting cDCs might provide potentially therapeutic applications in treating autoimmune related liver diseases.     

Syndecan‐1 identifies and controls the frequency of IL‐17‐producing naïve natural killer T (NKT17) cells in mice

Invariant natural killer T (iNKT) cells recognize glycolipids as antigens and diversify into NKT1 (IFN‐γ), NKT2 (IL‐4), and NKT17 (IL‐17) functional subsets while developing in the thymus. Mechanisms that govern the balance between these functional subsets are poorly understood due, partly, to the lack of distinguishing surface markers. Here we identify the heparan sulfate proteoglycan syndecan‐1 (sdc1) as a specific marker of naïve thymic NKT17 cells in mice and show that sdc1 deficiency significantly increases thymic NKT17 cells at the expense of NKT1 cells, leading to impaired iNKT cell‐derived IFN‐γ, both in vitro and in vivo. Using surface expression of sdc1 to identify NKT17 cells, we confirm differential tissue localization and interstrain variability of NKT17 cells, and reveal that NKT17 cells express high levels of TCR‐β, preferentially use Vβ8, and are more highly sensitive to ɑ‐GalCer than to CD3/CD28 stimulation. These findings provide a novel, noninvasive, simple method for identification, and viable sorting of naïve NKT17 cells from unmanipulated mice, and suggest that sdc1 expression negatively regulates homeostasis in iNKT cells. In addition, these findings lay the groundwork for investigating the mechanisms by which sdc1 regulates NKT17 cells.     

经链球菌菌体制剂OK-432刺激的树突状细胞对自然杀伤细胞增殖及功能的影响

目的:探讨经链球菌菌体制剂OK-432刺激的树突状细胞(Dendritic cells,DC)对自体自然杀伤细胞(Naturalkiller cells,NK)体外扩增和功能的影响。方法:将DC分为未成熟DC组和OK-432刺激的DC组,48小时后MTT法检测DC增殖情况,FCM检测DC表型CD80、CD83、CD86的表达情况;后将未成熟DC组和OK-432刺激的DC组分别与NK细胞以1∶1、1∶5、1∶10、1∶20、1∶40比例混合继续培养。0、2、4、6天时计算NK细胞扩增倍数;FCM检测NK细胞PFP、GraB、CD107a的表达;LDH释放法检测NK对HepG2细胞的杀伤活性。结果:OK-432(5μg/ml)使DC增殖达到最佳(30%),且能显著增强DC表型表达(P<0.05)。1∶5(OK-DC)组NK细胞扩增倍数达最大(P<0.05);1∶5(OK-DC)组能显著促进NK释放穿孔素(Pore-forming protein,PFP)、颗粒酶(Granzyme B,GraB)、CD107a(P<0.05);1∶5(OK-DC)组对HepG2细胞的杀伤活性(67.12±5.36)%达到最大(P<0.05)。结论:OK-432(终浓度5μg/ml)能促进DC增殖,并促进DC成熟;OK-DC与NK细胞共培养能以剂量依赖的方式增强NK细胞杀伤HepG2细胞功能,可能与增加NK扩增倍数和PFP、GraB、CD107a的表达有关。     

Thymus medulla fosters generation of natural Treg cells,invariant γδ T cells,and invariant NKT cells: What we learn from intrathymic migration

The organization of the thymus into distinct cortical and medullary regions enables it to control the step‐wise migration and development of immature T‐cell precursors. Such a process provides access to specialized cortical and medullary thymic epithelial cells at defined stages of maturation, ensuring the generation of self‐tolerant and MHC‐restricted conventional CD4⁺ and CD8⁺ αβ T cells. The migratory cues and stromal cell requirements that regulate the development of conventional αβ T cells have been well studied. However, the thymus also fosters the generation of several immunoregulatory T‐cell populations that form key components of both innate and adaptive immune responses. These include Foxp3⁺ natural regulatory T cells, invariant γδ T cells, and CD1d‐restricted invariant natural killer T cells (iNKT cells). While less is known about the intrathymic requirements of these nonconventional T cells, recent studies have highlighted the importance of the thymus medulla in their development. Here, we review recent findings on the mechanisms controlling the intrathymic migration of distinct T‐cell subsets, and relate this to knowledge of the microenvironmental requirements of these cells.     

Autoreactive natural killer T cells: promoting immune protection and immune tolerance through varied interactions with myeloid antigen-presenting cells

Natural killer T (NKT) cells are innate T lymphocytes that are restricted by CD1d antigen‐presenting molecules and recognize lipids and glycolipids as antigens. NKT cells have attracted attention for their potent immunoregulatory effects. Like other types of regulatory lymphocytes, a high proportion of NKT cells appear to be autoreactive to self antigens. Thus, as myeloid antigen‐presenting cells (APCs) such as monocytes, dendritic cells (DCs) and myeloid‐derived suppressor cells (MDSCs) constitutively express CD1d, NKT cells are able to interact with these APCs not only during times of immune activation but also in immunologically quiescent periods. The interactions of NKT cells with myeloid APCs can have either pro‐inflammatory or tolerizing outcomes, and a central question is how the ensuing response is determined. Here we bring together published results from a variety of model systems to highlight three critical factors that influence the outcome of the NKT–APC interaction: (i) the strength of the antigenic signal delivered to the NKT cell, as determined by antigen abundance and/or T‐cell receptor (TCR) affinity; (ii) the presence or absence of cytokines that costimulate NKT cells [e.g. interleukin (IL)‐12, IL‐18 and interferon (IFN)‐α]; (iii) APC intrinsic factors such as differentiation state (e.g. monocyte versus DC) and Toll‐like receptor (TLR) stimulation. Together with recent findings that demonstrate new links between NKT cell activation and endogenous lipid metabolism, these results outline a picture in which the functions of NKT cells are closely attuned to the existing biological context. Thus, NKT cells may actively promote tolerance until a critical level of danger signals arises, at which point they switch to activating pro‐inflammatory immune responses.     

Leishmania donovani‐induced expression of signal regulatory protein α on Kupffer cells enhances hepatic invariant NKT‐cell activation

Signal regulatory protein α (SIRPα) and its cognate ligand CD47 have been documented to have a broad range of cellular functions in development and immunity. Here, we investigated the role of SIRPα–CD47 signalling in invariant NKT (iNKT) cell responses. We found that CD47 was required for the optimal production of IFN‐γ from splenic iNKT cells following exposure to the αGalCer analogue PBS‐57 and in vivo infection of mice with Leishmania donovani. Surprisingly, although SIRPα was undetectable in the liver of uninfected mice, the hepatic iNKT‐cell response to infection was also impaired in CD47^?/? mice. However, we found that SIRPα was rapidly induced on Kupffer cells following L. donovani infection, via a mechanism involving G‐protein‐coupled receptors. Thus, we describe a novel amplification pathway affecting cytokine production by hepatic iNKT cells, which may facilitate the breakdown of hepatic tolerance after infection.     

Enhancement of the synthetic ligand-mediated function of liver NK1.1Ag+ T cells in mice by interleukin-12 pretreatment

We previously reported that mouse NK1.1 Ag+ T (NKT) cells activated by interleukin-12 (IL-12) act as anti-tumour/anti-metastatic effectors. However, IL-12 reportedly induces a rapid disappearance of liver NKT cells by activation-induced apoptosis. In the present study, however, we show that injection of IL-12 into mice merely down-regulates the NK1.1 expression of liver NKT cells and Vbeta8+ intermediate T-cell receptor cells and CD1d/alpha-galactosylceramide (alpha-GalCer)-tetramer reactive cells in the liver remained and did not decrease. Furthermore, when IL-12-pretreated (24 hr before) mice were injected with alpha-GalCer, not only serum interferon-gamma but also serum IL-4 concentrations increased several-fold in comparison to the control alpha-GalCer-injected mice. However, IL-12 pretreatment markedly up-regulated serum ALT levels and Fas-ligand expression on NKT cells after alpha-GalCer injection in middle-aged mice only. Consistently, the liver mononuclear cells (MNC) from IL-12-pretreated mice stimulated with alpha-GalCer in vitro produced much greater amounts of interferon-gamma and IL-4, and also showed a more potent cytotoxicity against tumour targets than those from mice pretreated with phosphate-buffered saline. Liver MNC from middle-aged mice, but not from young mice pretreated with IL-12, also showed increased cytotoxicity following in vitro alpha-GalCer stimulation against cultured hepatocytes. Furthermore, IL-12 treatment of middle-aged mice enhanced tumour necrosis factor receptor 1 mRNA expression in liver Vbeta8+ T cells, and in vitro experiments also revealed that IL-12 pretreatment of liver MNC from middle-aged mice enhanced their tumour necrosis factor-alpha production after alpha-GalCer stimulation. Synthetic ligand-mediated functions of NKT cells, including IL-4 production, are thus enhanced by IL-12 pretreatment.     

RASAL3, a novel hematopoietic RasGAP protein,regulates the number and functions of NKT cells

Ras GTPase‐activating proteins negatively regulate the Ras/Erk signaling pathway, thereby playing crucial roles in the proliferation, function, and development of various types of cells. In this study, we identified a novel Ras GTPase‐activating proteins protein, RASAL3, which is predominantly expressed in cells of hematopoietic lineages, including NKT, B, and T cells. We established systemic RASAL3‐deficient mice, and the mice exhibited a severe decrease in NKT cells in the liver at 8 weeks of age. The treatment of RASAL3‐deficient mice with α‐GalCer, a specific agonist for NKT cells, induced liver damage, but the level was less severe than that in RASAL3‐competent mice, and the attenuated liver damage was accompanied by a reduced production of interleukin‐4 and interferon‐γ from NKT cells. RASAL3‐deficient NKT cells treated with α‐GalCer in vitro presented augmented Erk phosphorylation, suggesting that there is dysregulated Ras signaling in the NKT cells of RASAL3‐deficient mice. Taken together, these results suggest that RASAL3 plays an important role in the expansion and functions of NKT cells in the liver by negatively regulating Ras/Erk signaling, and might be a therapeutic target for NKT‐associated diseases.     

Defective tumor necrosis factor alpha-induced maturation of monocyte-derived dendritic cells in patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are clonal stem cell disorders, characterized by ineffective and dysplastic hematopoiesis. MDS patients have a defective immune response manifested by increased susceptibility to bacterial infections, autoimmune phenomena, and high incidence of lymphoid malignancies. Presently, we investigated the phenotype and function of monocyte-derived dendritic cells (MoDC) in 23 MDS patients and 15 controls at different stages of differentiation using the maturation stimuli tumor necrosis factor-alpha (TNF-alpha) and LPS. Monocytes from MDS patients showed low potential to differentiate into dendritic cells (DC), as determined by low cell yield and CD1a expression. MDS-MoDCs exhibited low expression of mannose receptor and reduced endocytic capacity. MDS-MoDCs showed a diminished response to TNF-alpha with low CD83, CD80, and CD54 expression and allostimulatory capacity. In patients with 5q syndrome, monocytes and MoDCs were positive for the 5q deletion, suggesting their origin from the malignant clone. Our data indicate that MoDCs in MDS display quantitative and functional abnormalities that may contribute to the defective immune response of these patients.     

Expression of an avian CD6 candidate is restricted to αβ T cells,splenic CD8+ γδ T cells and embryonic natural killer cells

A candidate avian CD6 homolog is identified by the S3 monoclonal antibody. The S3 antigen exists in a phosphorylated glycoprotein form of 130 kDa and a nonphosphorylated form of 110 kDa. Removal of phosphate groups and N-linked carbohydrates indicates a 78-kDa protein core. During thymocyte differentiation, the γδ T cells do not express S3, whereas mature CD4⁺ and CD8⁺ cells of αβ lineage acquire S3 antigen. All αβ T cells in the blood and spleen express the S3 antigen at relatively high levels. In contrast, only the CD8⁺ sub-population of γδ T cells in the spleen expresses the antigen and neither αβ nor γδ T cells in the intestinal epithelium express the S3 antigen. The S3 antigen is also found on embryonic splenocytes with a phenotypic profile characteristic of avian natural killer cells. The biochemical characteristics and this cellular expression pattern imply that the S3 antigen is the chicken CD6 homolog.