Delphine Rossille

IL-2 Requirement for Human Plasma Cell Generation: Coupling Differentiation and Proliferation by Enhancing MAPK–ERK Signaling

Mature B cell differentiation involves a well-established transcription factor cascade. However, the temporal dynamics of cell signaling pathways regulating transcription factor network and coordinating cell proliferation and differentiation remain poorly defined. To gain insight into the molecular processes and extrinsic cues required for B cell differentiation, we set up a controlled primary culture system to differentiate human naive B cells into plasma cells (PCs). We identified T cell-produced IL-2 to be critically involved in ERK1/2-triggered PC differentiation. IL-2 drove activated B cell differentiation toward PC independently of its proliferation and survival functions. Indeed, IL-2 potentiated ERK activation and subsequent BACH2 and IRF8 downregulation, sustaining BLIMP1 expression, the master regulator for PC differentiation. Inhibition of the MAPK–ERK pathway, unlike STAT5 signaling, impaired IL-2–induced PC differentiation and rescued the expression profile of BACH2 and IRF8. These results identify IL-2 as a crucial early input in mature B cell fate commitment.

T-cell defect in diffuse large B-cell lymphomas involves expansion of myeloid-derived suppressor cells

In diffuse large B-cell lymphoma (DLBCL), the number of circulating monocytes and neutrophils represents an independent prognostic factor. These cell subsets include monocytic and granulocytic myeloid-derived suppressor cells (M- and G-MDSCs) defined by their ability to suppress T-cell responses. MDSCs are a heterogeneous population described in inflammatory and infectious diseases and in numerous tumors including multiple myeloma, chronic lymphocytic leukemia, and DLBCL. However, their mechanisms of action remain unclear. We broadly assessed the presence and mechanisms of suppression of MDSC subsets in DLBCL. First, a myeloid suppressive signature was identified by gene expression profiling in DLBCL peripheral blood. Accordingly, we identified, in a cohort of 66 DLBCL patients, an increase in circulating G-MDSC (Lin(neg)HLA-DR(neg)CD33(pos)CD11b(pos)) and M-MDSC (CD14(pos)HLA-DR(low)) counts. Interestingly, only M-MDSC number was correlated with the International Prognostic Index, event-free survival, and number of circulating Tregs. Furthermore, T-cell proliferation was restored after monocyte depletion. Myeloid-dependent T-cell suppression was attributed to a release of interleukin-10 and S100A12 and increased PD-L1 expression. In summary, we identified expanded MDSC subsets in DLBCL, as well as new mechanisms of immunosuppression in DLBCL.

Comparison of two enzymatic immunoassays, high resolution mass spectrometry method and radioimmunoassay for the quantification of human plasma histamine

Histamine (HA) is one of the main immediate mediators involved in allergic reactions. HA plasma concentration is well correlated with the severity of vascular and respiratory signs of anaphylaxis. Consequently, plasma quantification of HA is useful to comfort the diagnosis of anaphylaxis. Currently, radioimmunoassay (RIA) is the gold standard method to quantify HA due to its high sensitivity, but it is time consuming, implicates specific formations and cautions for technicians, and produces hazardous radioactive wastes. The aim of this study was to compare two enzymatic immunoassays (EIA) and one in-house liquid chromatography high-resolution mass spectrometry method (LC-HRMS) with the gold standard method for HA quantification in plasma samples of patients suspected of anaphylaxis reactions. Ninety-two plasma samples were tested with the 4 methods (RIA, 2 EIA and LC-HRMS) for HA quantification. Fifty-eight samples displayed HA concentrations above the positive cut-off of 10nM evaluated by RIA, including 18 highly positive samples (>100 nM). This study shows that Immunotech(®) EIA and LC-HRMS concentrations were highly correlated with RIA values, in particular for samples with a HA concentration around the positive cut-off. In our hands, plasma concentrations obtained with the Demeditec Diagnostics(®) EIA correlated less with results obtained by RIA, and an underestimation of plasma HA levels led to a lack of sensitivity. In conclusion, this study demonstrates that Immunotech(®) EIA and LC-HRMS method could be used instead of RIA to assess plasma HA in human diagnostic use.

Prédire l’accès à la liste d’attente de transplantation rénale: comparaison de deux méthodes de fouille de données

The study compares the effectiveness of Bayesian networks versus Decision Trees for predicting access to the renal transplant waiting list in a French healthcare network. The data set consisted in 809 patients starting renal replacement therapy. The data were randomly devised in a training set (90 %) and a validation set (l0 %). Bayesian networks and CART decision tree were built on the training set. Their predictive performances were compared on the validation set. The Age variable was found to be the most important factor for predicting registration on the waiting list in both models. Both models were highly sensitive and specific: sensitivity 90.0 % (95 % CI: 76.8–100), specificity 96.7% (95 % CI: 92.2–100). Moreover, the models were complementary since the Bayesian network provided a global view of the variables’ associations while the decision tree was more easily interpretable by physicians. These approaches provide insights on the current care process. This knowledge could be used for optimizing the healthcare process.