MULTIPHYSICS MODELISATION OF AN UNPROTECTED LOSS OF FLOW TRANSIENT IN A SODIUM COOLED FAST REACTORS USING A NEUTRONIC-THERMAL-HYDRAULIC COUPLING SCHEME

Sodium cooled fast neutron reactors (SFR) are one of the selected reactor concepts in the framework of the Generation IV International Forum. In this concept, unprotected loss of cooling flow transients (ULOF), for which the non-triggering of backup systems is postulated, are regarded as potential initiators of core melting accidents. During an ULOF transient, spatial distributions of fuel, structure and sodium temperatures are affected by the core cooling flow decrease, which will modify the spatial and energy distribution of neutron in the core due to the spatial competition of neutron feedback effects. As no backup systems are triggered, sodium may reach its boiling temperature at some point, leading to local sodium density variations and making the transient fluctuate in a two-phase flow physics where thermal-hydraulics and neutronics may interact with each other. The transient phenomenology involves several physic disciplines at different time and spatial scales, such as core neutronics, coolant thermal-hydraulics and fuel thermo-mechanics. This paper presents the results of thermal-hydraulic/neutronic coupled simulations of an ULOF transient on the SFR project ASTRID. These coupled calculations are based on the supervisor platform SALOME to link the neutron code APOLLO3® to the system thermal-hydraulic code CATHARE3. The physical approach used by the coupling to describe the neutron kinetic is a quasi-static adiabatic one, updating the normalized spatial power distribution periodically by performing static neutron calculations, while a point kinetic model associated to a neutron feedback model calculates the power amplitude variations.

NEUTRONIC MODELING OF A FAST CORE WITH MODERATING MATERIALS USING APOLLO3R CODE

In order to improve passive safety of Sodium-cooled Fast Reactors The French Alternative Energies and Atomic Energy Commission (CEA) has proposed a new core design called CADOR - an SFR core with enhanced Doppler reactivity feedback. One of its most important design features is the introduction of solid moderating materials inside each fuel assemblies to slightly decrease the average neutron energy. The article focuses on development and validation of a neutronics calculation scheme able to produce accurate results in case of CADOR and other fast cores with moderating materials. The study uses two different fuel assembly models moderated by metallic beryllium and zirconium hydride (ZrH2) respectively The study includes discussion of neutron scattering treatment and different ways of spatial homogenization and energy condensations. The results indicate that the accurate scattering treatment leads to much better estimation of Doppler constant, especially in case of ZrH2 moderated core. By using combined deterministic-Monte Carlo calculation scheme we are able to quantify the biases on global reactivity, reactivity feedbacks and control rod worth. We demonstrate that spatial homogenization plays a more important role in case of moderated CADOR assemblies and thus preserving certain level of heterogeneity within fuel assemblies can lower the calculation bias significantly.

Heterogeneity of anti-β2-glycoprotein I antibodies

The aim of this study was to evaluate the heterogeneity of IgG-anti- β2 -glycoprotein I antibodies (IgG-aβ2 GPI) as regarding their reactivity pattern against different sources of human β2 GPI,their avidity and their association with clinical events of antiphospholipid syndrome (APS).Three thousand six hundred and eightyfour consecutive patient sera were routinely tested for IgG-a β2 GPI over 1 year using an in-house ELISA with 2 different commercial preparations of human purified β2GPI. Of the 340 sera found positive, all those clinically documented were included in this study; 61 were positive with only one preparation (S1) and 59 with both (S2).The results of ELISA were confirmed by Western blot. Heterogeneity was stressed by testing sera with a human recombinant protein and 3 β2 GPI-related peptides. No contribution of glycosylation in the binding to β2GPI was found.The avidity indices for each protein were significantly higher in S1 than in S2 (p = 0.0021). S2 were more associated with antiphospholipid antibodies than S1 (75% versus 21% ; p <0.0001).A similar frequency of the main clinical features of APS was found in S1 and S2 sera (69% and 71%, respectively). In conclusion, our data show a heterogeneity in the antigenic reactivity pattern of IgG- a β2 GPI and a relationship between a binding profile and antibody avidity.This heterogeneity could represent a crucial factor of variability in test results and underlines the difficulty of getting standardisation.

Balance between activating NKG2D, DNAM-1, NKp44 and NKp46 and inhibitory CD94/NKG2A receptors determine natural killer degranulation towards rheumatoid arthritis synovial fibroblasts

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and synovial hyperplasia leading to progressive joint destruction. Fibroblast-like synoviocytes (FLS) are central components of the aggressive, tumour-like synovial structure termed pannus, which invades the joint space and cartilage. A distinct natural killer (NK) cell subset expressing the inhibitory CD94/NKG2A receptor is present in RA synovial fluid. Little is known about possible cellular interactions between RA-FLS and NK cells. We used cultured RA-FLS and the human NK cell line Nishi, of which the latter expresses an NK receptor repertoire similar to that of NK cells in RA synovial fluid, as an in vitro model system of RA-FLS/NK cell cross-talk. We show that RA-FLS express numerous ligands for both activating and inhibitory NK cell receptors, and stimulate degranulation of Nishi cells. We found that NKG2D, DNAM-1, NKp46 and NKp44 are the key activating receptors involved in Nishi cell degranulation towards RA-FLS. Moreover, blockade of the interaction between CD94/NKG2A and its ligand HLA-E expressed on RA-FLS further enhanced Nishi cell degranulation in co-culture with RA-FLS. Using cultured RA-FLS and the human NK cell line Nishi as an in vitro model system of RA-FLS/NK cell cross-talk, our results suggest that cell-mediated cytotoxicity of RA-FLS may be one mechanism by which NK cells influence local joint inflammation in RA.

Anti-NKG2A autoantibodies in a patient with systemic lupus erythematosus

OBJECTIVES

To characterize a novel anti-NKG2A autoantibody detected in a patient with SLE during a severe flare, and in a cross-sectional study investigate the occurrence of such autoantibodies in patients with SLE and primary SS (pSS).

METHODS

Serum or IgG from patients with SLE, pSS and healthy volunteers were assayed for blocking of anti-NKG2A or HLA-E binding to peripheral blood mononuclear cells or CD94/NKG2A- and CD94/NKG2C-transfected Ba/F3 cells. The anti-NKG2A autoantibodies were evaluated for effect on NK cell degranulation in response to HLA-E-transfected K562 cells. IFN-α was determined by an immunoassay and disease activity by the SLEDAI score.

RESULTS

Anti-NKG2A autoantibodies, which blocked binding of HLA-E tetramers to CD94/NKG2A-transfected cells and impaired NKG2A-mediated inhibition of NK cell activation, were observed in a patient with SLE. The presence of anti-NKG2A autoantibodies was associated with high SLE disease activity (SLEDAI score 14 and 16) and increased serum IFN-α. Of 94 SLE, 60 pSS and 30 healthy donor sera, only the index patient serum contained anti-NKG2A autoantibodies.

CONCLUSION

The presence of autoantibodies targeting NKG2A is a rare event, but when such autoantibodies occur they may promote excessive NK cell function. This can contribute to the pathogenesis by increasing the killing of cells and the release of autoantigens. Our findings highlight the possible importance of NK cells in the SLE disease process.

Autoimmunity, spontaneous tumourigenesis, and IL-15 insufficiency in mice with a targeted disruption of the tumour suppressor gene Fus1

The Fus1 gene resides in the critical 3p21.3 human chromosomal region deleted in lung and breast cancers. Recently, the tumour suppressor properties of Fus1 were confirmed experimentally by intra-tumoural administration of Fus1 that suppressed experimental lung metastasis in mice. We generated Fus1-deficient mice that were viable, fertile, and demonstrated a complex immunological phenotype. Animals with a disrupted Fus1 gene developed signs of autoimmune disease, such as vasculitis, glomerulonephritis, anaemia, circulating autoantibodies, and showed an increased frequency of spontaneous vascular tumours. Preliminary analysis of immune cell populations revealed a consistent defect in NK cell maturation in Fus1 null mice that correlated with changes in the expression of IL-15. Injection of IL-15 into Fus1 knockout mice completely rescued the NK cell maturation defect. Based on these results, we propose the hypothesis that Fus1 deficiency affects NK cell maturation through the reduction of IL-15 production but does not directly alter their developmental capacity. Since acquired immunity was not affected in Fus1-deficient animals, we suggest a relationship between the Fus1 protein and the regulation of innate immunity via IL-15 production. The increased frequency of spontaneous cancers and the development of an autoimmune syndrome in Fus1 null mice imply that these mice could serve as a model for studying molecular mechanisms of anti-tumour immunity and autoimmunity.

Functional evidence supporting the predicted role of KIR3DS1 in the host response to HIV: KIR3DS1 is an activating receptor expressed by human Natural Killer cells (52.5)

KIR3DL1 is a highly polymorphic inhibitory Killer cell Immunoglobulin-like (KIR) Receptor gene with at least 23 alleles described, including its activating counterpart KIR3DS1. Recently, the KIR3DS1 allele has been shown to slow progression to AIDS in HLABw4*80I individuals. However, due to the lack of specific anti-KIR3DS1 antibody, expression and function have never been reported. In a study of 64 donors, we demonstrate KIR3DS1 expression on a substantial subset of peripheral Natural Killer (NK) cells through its recognition by the monoclonal antibody Z27. The fidelity of this detection method was confirmed by analysis of KIR3DS1 transfectants and the identification of a novel KIR3DS1 null allele. Furthermore, we show that ligation of KIR3DS1 by Z27 leads to NK cell degranulation and interferon gamma secretion. Finally, we document the persistence of KIR3DS1+ NK cells in HIV1 viremic patients. In conclusion, the high frequency of KIR3DS1 expression, together with its ability to activate NK cells, and its maintenance during HIV-1 viremia support the epidemiological data suggesting a critical role for this receptor in controlling HIV-1 pathogenesis.

This project has been funded in part with Federal funds from the NCI and the NIH, under DHHS #N01-C0-12400.

Genetic control of variegated KIR gene expression: polymorphisms of the bi-directional KIR3DL1 promoter are associated with distinct frequencies of gene expression (35.37)

The recent discovery of the bi-directional nature of the KIR gene promoters suggests that the relative strength of competing sense and antisense promoter elements might affect the probability of gene expression. Analysis of a panel of donors has revealed the presence of several functionally relevant promoter polymorphisms, clustered mainly in the inhibitory KIR family members, especially the KIR3DL1 alleles. The percentage of peripheral blood NK cells expressing either KIR3DL1 or KIR3DS1 was evaluated in individuals heterozygous at this locus. The KIR3DL1*001 and KIR3DS1 alleles were found to be expressed on a significantly higher percentage of NK cells than all other KIR3DL1 alleles. High frequency of expression was associated with a specific promoter polymorphism at a Sp1 transcription factor-binding site, and this change increased the relative promoter activity in the sense orientation. The KIR2DS4 promoter region is nearly identical to the KIR3DL1 promoter, and several polymorphisms are present, however none of the KIR2DS4 polymorphisms affect promoter activity in vitro and no association was observed between promoter polymorphisms and frequency of expression.

This research was supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research. Funded by NCI Contract N01-CO-12400

Identification of probabilistic transcriptional switches in the Ly49 gene cluster: a eukaryotic mechanism for selective gene activation

Murine natural killer cells selectively express members of the Ly49 family of class I MHC receptors; however, the molecular mechanism controlling probabilistic expression of Ly49 proteins has not been defined. A pair of overlapping, divergent promoters discovered in the Ly49g gene functions as a molecular switch that can produce a forward transcript containing the coding region of the gene (on position) or a noncoding transcript in the opposite direction (off position), and this element maintains transcription in the chosen direction. Competition of C/EBP and TBP transcription factors for overlapping binding sites determines the relative strength of the competing promoters and the probability of transcription in a given direction. Similar elements precede all Ly49 family members, and the relative strength of the forward promoter in each inhibitory Ly49 gene correlates with the percentage of natural killer cells that express a given receptor, supporting a promoter competition model of selective gene activation.

Analysis of donor NK and T cells infused in patients undergoing MHC-matched allogeneic hematopoietic transplantation

We retrospectively analyzed the percentages and absolute numbers of T cells, natural killer (NK) cells and NK cell subsets in cryopreserved samples of either bone marrow or blood non-T cell-depleted allogeneic MHC-matched hematopoietic grafts. Using flow cytometry, we found higher numbers of NK cells in aphereses than in bone marrow collections. We further investigated the distribution of NK cell subsets, defined by the cell surface expression of MHC class I-specific receptors, in these allogeneic grafts. The distribution of NK cell subsets from the two different origins were similar, with the exception of the CD158a/h(+) NK cell subset, whose size appeared to be smaller in bone marrow. The search for relations between the numbers of infused cells and post-transplantation events demonstrated that increasing numbers of infused T cells but not NK cells are related with decreased overall survival. Our study highlights the toxicity of infused T cells but not NK cells in allogeneic MHC-matched hematopoietic grafts. These data pave the way for further trials to investigate the effect of NK cell infusion in MHC-matched allogeneic transplantation, and in particular whether ex vivo NK cell expansion and activation may enhance the anti-tumoral effect of the procedure and decrease its morbidity.

Biology of T memory type 1 cells

Engagement of inhibitory natural killer (NK) cell receptors for MHC class I molecules (NKR) can impair NK-cell activation programs. Inhibitory NKR thus confer to NK cells the capacity to discriminate between MHC class I+ and MHC class I- target cells, and are therefore involved in the control of NK-cell tolerance to self, as well as in the elimination of MHC class I- distressed cells by NK cells. In human and mouse, a subset of alphabeta T cells also express inhibitory NKR at their surface, but the biological function of inhibitory NKR on T cells remains to be precisely elucidated. We refer to these cells as T memory type 1 (Tm1) cells, and review here the phenotypic and functional features of this subset of memory-phenotype CD8+ alphabeta T cells. In vitro studies suggest that inhibitory NKR are involved in the peripheral control of T-cell self-tolerance. In vitro and in vivo analysis have revealed a novel biological function for inhibitory NKR when expressed on T cells. Indeed, engagement of inhibitory NKR on T cells provides them with survival signals against activation-induced cell death. Thus, sensing of self-MHC class I molecules by inhibitory NKR displayed on alphabeta T cells leads to the in vivo accumulation of Tm1 cells.

Lead poisoning secondary to hyperthyroidism: report of two cases

With long-term exposure to lead, lead accumulates in bone, where it is stored for years. These quiescent lead stores are mobilised when increased bone turnover occurs, and latent lead toxicity may then become symptomatic. Although Graves' disease is a common cause of increased bone turnover, to date hyperthyroidism has been implicated in lead poisoning only twice. We describe herein two cases of hyperthyroidism, one caused by toxic multinodular thyroid enlargement, the second by Graves' disease, leading to lead poisoning. Treatment of hyperthyroidism with radioactive iodine cured both hyperthyroidism and lead poisoning and no chelating agent therapy was necessary. Lead poisoning is an important environmental health problem, and physicians must be aware of the endocrine disorders such as hyperthyroidism and hyperparathyroidism that increase bone turnover, favouring lead mobilisation. Atypical symptoms should draw the physician's attention to the possibility of lead poisoning, particularly in workers with occupational exposure to lead and in areas where lead poisoning is endemic.

A pharmacodynamic study of morphine and its glucuronide metabolites after single morphine dosing in cancer patients with pain

Eleven morphine naïve patients with cancer-related pain were given a single dose of either intravenous morphine (n = 5) or oral morphine (n = 6). Blood sampling was performed over a 24-hr period and serial pain assessments were made using a categorical scale. Plasma samples were analyzed for morphine, morphine-6-glucuronide (M-6-G), morphine-3-glucuronide (M-3-G), and normorphine using high-performance liquid chromatography. In neither the intravenous nor oral group was there a correlation between analgesia duration and the half-lives of morphine and M-6-G. There was no correlation between the time to peak analgesia and time to peak concentration for morphine or M-6-G. There was no significant difference in absolute concentrations of M-6-G or M-3-6 nor in the ratio of M-3-G to M-6-G at peak analgesia versus relapse.

[Value of ketoconazole in the treatment of Cushing disease]

Ketoconazole has been successfully used in short-term treatment of Cushing's syndrome. We treated 4 patients who had Cushing's disease with ketoconazole administered during 5 to 18 months. Two of them are still controlled after 15 months of treatment and 7 months after treatment was withdrawn. In the other two patients, treatment was ineffective primarily and after 5 months. Our data confirm the usefulness of ketoconazole in the treatment of Cushing's disease, but they also show that primary resistance and tachyphylaxis in long-term treatment may occur, as previously reported.