233 research outputs found
Lymphocytes B mémoire dans la réponse humorale anti- HLA en transplantation d'organe
Les alloanticorps anti-HLA sont dirigĂ©s vis-Ă -vis de diffĂ©rents Ă©pitopes des molĂ©cules du systĂšme HLA. Cette immunisation survient lors d'une transplantation d'organe, de transfusions sanguines ou d'une grossesse. On retrouve aussi ces anticorps, lorsque les techniques de dĂ©tection sont sensibles, en l'absence de tout Ă©vĂšnement immunisant. En transplantation d'organe, rĂ©nale en particulier, la prĂ©sence d anticorps anti-HLA, du fait des lĂ©sions de rejet humoral qu'ils induisent, constitue une des premiĂšres causes de perte de fonction des greffons Ă moyen et long terme. NĂ©anmoins, les cellules lymphocytaires qui sont la source de ces anticorps anti-HLA demeurent mal identifiĂ©es.Dans la premiĂšre partie de ce travail, nous avons Ă©tudiĂ©, dans une cohorte de patients en attente de transplantation rĂ©nale, la distribution des diffĂ©rentes sous-populations lymphocytaires B circulantes par cytomĂ©trie de flux en relation avec la nature des Ă©vĂšnements immunisants vis-Ă -vis du systĂšme HLA, la prĂ©sence et la diversitĂ© des anticorps anti-HLA. Nous avons Ă©tudiĂ© en parallĂšle les concentrations sĂ©riques de BAFF ("B cell activating factor belonging to the TNF family"), principal facteur impliquĂ© dans la survie et la diffĂ©renciation des lymphocytes B matures. Nous avons retrouvĂ© une association entre la prĂ©sence et la diversitĂ© des anticorps anti-HLA, et l'augmentation de la proportion de lymphocytes B naĂŻfs activĂ©s Bm2, par rapport aux autres sous-populations lymphocytaires B, et indĂ©pendamment de l'existence d'Ă©vĂšnements immunisants. Les concentrations sĂ©riques de BAFF Ă©taient Ă©galement associĂ©es positivement Ă la prĂ©sence et Ă la diversitĂ© des anticorps anti-HLA. Ces donnĂ©es suggĂšrent que l'augmentation des lymphocytes B naĂŻfs activĂ©s et des concentrations sĂ©riques de BAFF favorise le dĂ©veloppement des anticorps anti-HLA Ă la suite d'un Ă©vĂ©nement immunisant. A l'instar du mĂ©canisme Ă©voquĂ© en auto-immunitĂ©, BAFF pourrait intervenir en prĂ©sence de l'alloantigĂšne en favorisant la survie de clones B allorĂ©actifs.Dans la deuxiĂšme partie de notre travail, nous nous sommes intĂ©ressĂ©s plus particuliĂšrement Ă l'implication des lymphocytes B mĂ©moire allorĂ©actifs dans la rĂ©ponse humorale anti-HLA. Pour dĂ©tecter les lymphocytes B mĂ©moire circulants, nous avons utilisĂ© un test de stimulation polyclonale permettant leur diffĂ©renciation en plasmablastes puis nous avons recherchĂ© et Ă©tudiĂ© la spĂ©cificitĂ© des anticorps anti-HLA produits dans les surnageants de culture. Un premier rĂ©sultat important a Ă©tĂ© la possibilitĂ© de dĂ©tecter, chez les patients prĂ©sentant des anticorps anti-HLA, des lymphocytes B mĂ©moire allorĂ©actifs circulants plusieurs annĂ©es aprĂšs un Ă©vĂ©nement immunisant. En deuxiĂšme lieu, la prĂ©sence de ces lymphocytes B mĂ©moire Ă©tait associĂ©e au nombre d'Ă©vĂšnements immunisants. En effet, les patients ayant dĂ©veloppĂ©, en l'absence d'Ă©vĂ©nement immunisant des anticorps anti-HLA - dont nous montrons par ailleurs le caractĂšre potentiellement pathogĂšne - n'ont pas prĂ©sentĂ© de lymphocytes B mĂ©moire allorĂ©actifs circulants. Enfin, Ă l'aide du logiciel HLAMatchmaker, nous avons montrĂ© que les anticorps produits par les lymphocytes B mĂ©moire Ă©taient dirigĂ©s contre un nombre restreint d'Ă©pitopes partagĂ©s par plusieurs antigĂšnes HLA, ce qui suggĂšre une oligoclonalitĂ© du contingent B mĂ©moire allorĂ©actif. Chez les mĂȘmes patients, les anticorps anti-HLA circulants prĂ©sentaient une diversitĂ© de spĂ©cificitĂ© plus large, Ă©tant dirigĂ©s contre de multiples Ă©pitopes HLA. Ces rĂ©sultats suggĂšrent l'existence d'au moins deux types de rĂ©ponse humorale vis-Ă -vis des alloantigĂšnes HLA : l'une aboutissant Ă la production de lymphocytes B mĂ©moire et de plasmocytes Ă la suite d'une rĂ©action de centre germinatif T-dĂ©pendante, l'autre impliquant seulement des plasmocytes, possiblement issus de rĂ©ponses extra-folliculaires. Les facteurs orientant vers l un ou l autre type de rĂ©ponse sont encore mal dĂ©finis mais pourraient impliquer la dose et la voie d'exposition aux alloantigĂšnes.Anti-HLA antibodies are directed against various epitopes of HLA molecules. They develop during organ transplantations, red cell transfusions or pregnancies. But anti-HLA antibodies are also detected with sensitive assays in the absence of any sensitizing event. In renal transplantation, anti-HLA antibodies, through the development of antibody-mediated rejection, represent the first cause of late allograft loss. Nevertheless, the mechanisms and the exact nature of B cells involved in anti-HLA antibodies synthesis are poorly understood.In a first part, we studied by flow cytometry in patients awaiting kidney transplantation the distribution of the different peripheral B cell subsets in relation with immunizing events, titer and diversity of anti-HLA antibodies. We also studied the serum levels of BAFF ("B cell activating factor belonging to the TNF family"), the main factor involved in survival and differentiation of mature B cells. We found an association between the presence and the diversity of anti-HLA antibodies, and the proportion of activated naive Bm2 B cells, at the expense of other subsets, independently of immunizing events. BAFF serum levels were also positively associated with the presence and the diversity of anti-HLA antibodies. These data suggest that the increase in activated naive B cells and in BAFF levels facilitate the development of anti-HLA antibodies, following an immunizing event. Similarly to what is observed in autoimmunity, BAFF could help to the positive selection of alloreactive B cell clones, in the presence of alloantigen.In a second part, we focused on the role of circulating alloreactive memory B cells in anti-HLA humoral response. To detect those alloreactive memory B cells, we used a polyclonal stimulation assay allowing the differentiation of memory B cells into plasmablasts and we studied the specificity of anti-HLA antibodies recovered from culture supernatant. A first important result was the detection, decades after an imunizing event, of specific alloreactive memory B cells, even in the absence of the antigen. The detection of those circulating alloreactive memory B cells was related to the strength of immunizing events, i.e. the number of different immunizing events in the history of patients. Indeed, patients with anti-HLA antibodies with no history of immunizing event had no circulating alloreactive memory B cells. Eventually, with HLAMatchmaker software, we showed that antibodies produced by memory B cells were directed against a limited number of epitopes shared by HLA antigens, which suggests an oligoclonality of the alloreactive memory B cell population. By comparison, serum antibodies displayed a greater diversity, with multiple epitopic specificities. These results suggest two distinct cellular arms of humoral response towards HLA epitopes: medullar plasma cells, involved in long term HLA antibodies synthesis, and memory B cells waiting for a recall response in the presence of the antigen. The factors involved in the choice of those two cellular fates are poorly understood but may involve dose and route of exposition to the alloantigen.PARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF
Home and Office Blood Pressure Monitoring in Renal Transplant Recipients
Background. Arterial hypertension in renal transplant recipients (RTR) is associated with increased morbid mortality. In the general population, home blood pressure monitoring (HBPM) was found to be superior to office blood pressure (OBP) in identifying true hypertensive patients. The aim of this study was to investigate HBPM for the assessment of blood pressure profile in RTR. Methodology and Principal Findings. We included prospectively 87 stable RTR. Sitting OBP was measured during the outpatient clinic. HBPM was performed by measuring BP every morning and night for 4 days. The accepted limits for the OBP and HBPM, were respectively, 140/90âmmHg and 135/85âmmHg. Patients were classified as ânormotensive,â âuncontrolled,â âwhite-coat hypertensiveâ and âmasked hypertensiveâ, (OBP below the limit and HBPM above). During the study, 81 patients (55 males, age 48.5 ± 14 years) were available for analysis. The mean OBP and HBP were 138/83 ± 14/10âmmHg and 133/79 ± 14/8âmmHg; 29% of patients were uncontrolled, 28% normotensive, 21% white coat, and 21% masked hypertensive. Age, glycemia, and number of antihypertensive drugs were associated with hypertension. Conclusion and Significance. In RTR, HBPM is well accepted and better define BP profile since there is 42% discrepancy between OBPM and HBPM. Whether this discrepancy is associated with worst outcome in the long term remains to be demonstrated
Structure of the human activating natural cytotoxicity receptor NKp30 bound to its tumor cell ligand B7-H6
As revealed by the first crystal structure of a natural cytotoxicity receptor bound to its ligand, NKp30 engages B7-H6 in a manner structurally distinct from that of other CD28 family members
Role of simian virus 40 in cancer incidence in solid organ transplant patients
Transplant recipients have an increased risk of developing cancer in comparison with the general population. We present here data on cancer development in transplanted subjects who received organs from donors whose DNA was previously examined for the genomic insertion of Simian Virus 40 (SV40). Active follow-up of 387 recipients of solid organs donated by 134 donors, not clinically affected by cancer, was performed through the National Transplant Center (NTC). The average length of follow-up after transplant was 671±219 days (range 0â1085 days). Out of 134 proposed donors, 120 were utilised for organ donation. Of these, 12 (10%) were classified as positive for SV40 genomic insertion. None of the 41 recipients of organs from SV40 positive donors developed a tumour during the follow-up. In all, 11 recipients of organs given by SV40 negative donors developed a tumour (cancer incidence: 0.015 per year). In conclusion, cancer rates observed in our study are comparable to what reported by the literature in transplanted patients. Recipients of solid organs from SV40 positive donors do not have an increased risk of cancer after transplant. The role of SV40 in carcinogenesis in transplanted patients may be minimal
Disentangling molecular and clinical stratification patterns in beta-galactosidase deficiency
INTRODUCTION: This study aims to define the phenotypic and molecular spectrum of the two clinical forms of ÎČ-galactosidase (ÎČ-GAL) deficiency, GM1-gangliosidosis and mucopolysaccharidosis IVB (Morquio disease type B, MPSIVB). METHODS: Clinical and genetic data of 52 probands, 47 patients with GM1-gangliosidosis and 5 patients with MPSIVB were analysed. RESULTS: The clinical presentations in patients with GM1-gangliosidosis are consistent with a phenotypic continuum ranging from a severe antenatal form with hydrops fetalis to an adult form with an extrapyramidal syndrome. Molecular studies evidenced 47 variants located throughout the sequence of the GLB1 gene, in all exons except 7, 11 and 12. Eighteen novel variants (15 substitutions and 3 deletions) were identified. Several variants were linked specifically to early-onset GM1-gangliosidosis, late-onset GM1-gangliosidosis or MPSIVB phenotypes. This integrative molecular and clinical stratification suggests a variant-driven patient assignment to a given clinical and severity group. CONCLUSION: This study reports one of the largest series of b-GAL deficiency with an integrative patient stratification combining molecular and clinical features. This work contributes to expand the community knowledge regarding the molecular and clinical landscapes of b-GAL deficiency for a better patient management
Thiopurine Methyltransferase Predicts the Extent of Cytotoxicty and DNA Damage in Astroglial Cells after Thioguanine Exposure
Thiopurine methyltransferase (Tpmt) is the primary enzyme responsible for deactivating thiopurine drugs. Thiopurine drugs (i.e., thioguanine [TG], mercaptopurine, azathioprine) are commonly used for the treatment of cancer, organ transplant, and autoimmune disorders. Chronic thiopurine therapy has been linked to the development of brain cancer (most commonly astrocytomas), and Tpmt status has been associated with this risk. Therefore, we investigated whether the level of Tpmt protein activity could predict TG-associated cytotoxicity and DNA damage in astrocytic cells. We found that TG induced cytotoxicity in a dose-dependent manner in Tpmt+/+, Tpmt+/â and Tpmtâ/â primary mouse astrocytes and that a low Tpmt phenotype predicted significantly higher sensitivity to TG than did a high Tpmt phenotype. We also found that TG exposure induced significantly more DNA damage in the form of single strand breaks (SSBs) and double strand breaks (DSBs) in primary astrocytes with low Tpmt versus high Tpmt. More interestingly, we found that Tpmt+/â astrocytes had the highest degree of cytotoxicity and genotoxicity (i.e., IC50, SSBs and DSBs) after TG exposure. We then used human glioma cell lines as model astroglial cells to represent high (T98) and low (A172) Tpmt expressers and found that A172 had the highest degree of cytoxicity and SSBs after TG exposure. When we over-expressed Tpmt in the A172 cell line, we found that TG IC50 was significantly higher and SSB's were significantly lower as compared to mock transfected cells. This study shows that low Tpmt can lead to greater sensitivity to thiopurine therapy in astroglial cells. When Tpmt deactivation at the germ-line is considered, this study also suggests that heterozygosity may be subject to the greatest genotoxic effects of thiopurine therapy
Practical Recommendations for Long-term Management of Modifiable Risks in Kidney and Liver Transplant Recipients
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