Clonal Progression during the T Cell-Dependent B Cell Antibody Response Depends on the Immunoglobulin DH Gene Segment Repertoire

The diversity of the third complementarity determining region of the IgH chain is constrained by natural selection of immunoglobulin diversity (D(H)) sequence. To test the functional significance of this constraint in the context of thymus-dependent (TD) immune responses, we immunized BALB/c mice with WT or altered D(H) sequence with 2-phenyloxazolone-coupled chicken serum albumin (phOx-CSA). We chose this antigen because studies of the humoral immune response to the hapten phOx were instrumental in the development of the current theoretical framework on which our understanding of the forces driving TD responses is based. To allow direct comparison, we used the classic approach of generating monoclonal Ab (mAb) from various stages of the immune response to phOx to assess the effect of changing the sequence of the D(H) on clonal expansion, class switching, and affinity maturation, which are hallmarks of TD responses. Compared to WT, TD-induced humoral IgM as well as IgG antibody production in the D-altered ΔD-DμFS and ΔD-iD strains were significantly reduced. An increased prevalence of IgM-producing hybridomas from late primary, secondary, and tertiary memory responses suggested either impaired class switch recombination (CSR) or impaired clonal expansion of class switched B cells with phOx reactivity. Neither of the D-altered strains demonstrated the restriction in the V(H)/V(L) repertoire, the elimination of V(H)1 family-encoded antibodies, the focusing of the distribution of CDR-H3 lengths, or the selection for the normally dominant Ox1 clonotype, which all are hallmarks of the anti-phOx response in WT mice. These changes in clonal selection and expansion, as well as CSR indicate that the genetic constitution of the D(H) locus, which has been selected by evolution, can strongly influence the functional outcome of a TD humoral response

The complexity of biological control systems: An autophagy case study.

Funder: UK Dementia Research Institute; Id: http://dx.doi.org/10.13039/501100017510Autophagy and YAP1-WWTR1/TAZ signalling are tightly linked in a complex control system of forward and feedback pathways which determine different cellular outcomes in differing cell types at different time-points after perturbations. Here we extend our previous experimental and modelling approaches to consider two possibilities. First, we have performed additional mathematical modelling to explore how the autophagy-YAP1 crosstalk may be controlled by posttranslational modifications of components of the pathways. Second, since analogous contrasting results have also been reported for autophagy as a regulator of other transduction pathways engaged in tumorigenesis (Wnt/β-catenin, TGF-β/Smads, NF-kB or XIAP/cIAPs), we have considered if such discrepancies may be explicable through situations involving competing pathways and feedback loops in different cell types, analogous to the autophagy-YAP/TAZ situation. Since distinct posttranslational modifications dominate those pathways in distinct cells, these need to be understood to enable appropriate cell type-specific therapeutic strategies for cancers and other diseases.We are grateful for funding from the UK Dementia Research Institute (funded by MRC, Alzheimer’s Research UK and the Alzheimer’s Society), a grant of the Romanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0733, within PNCDI-III, and POC/448/1/1/127606 CENEMED project (M.P.)

α-Catenin levels determine direction of YAP/TAZ response to autophagy perturbation

The factors regulating cellular identity are critical for understanding the transition from health to disease and responses to therapies. Recent literature suggests that autophagy compromise may cause opposite effects in different contexts by either activating or inhibiting YAP/TAZ co-transcriptional regulators of the Hippo pathway via unrelated mechanisms. Here, we confirm that autophagy perturbation in different cell types can cause opposite responses in growth-promoting oncogenic YAP/TAZ transcriptional signalling. These apparently contradictory responses can be resolved by a feedback loop where autophagy negatively regulates the levels of α-catenins, LC3-interacting proteins that inhibit YAP/TAZ, which, in turn, positively regulate autophagy. High basal levels of α-catenins enable autophagy induction to positively regulate YAP/TAZ, while low α-catenins cause YAP/TAZ activation upon autophagy inhibition. These data reveal how feedback loops enable post-transcriptional determination of cell identity and how levels of a single intermediary protein can dictate the direction of response to external or internal perturbations

Analysis and study of the hysteretic properties in thermo-piezo- and photo-switchable spin-transition compounds

L objet principal de ce travail est l étude des propriétés de commutation de composés à transition de spin à l aide de la méthode FORC (First Order Reversal Curves), développé récemment dans le but de caractériser les matériaux magnétiques, et que nous avons adapté pour ce présent champ d investigation. Notre travail contient trois parties. La première partie concerne l application de la présente méthode à l étude des hystérésis thermo-induits des composés à transition de spin de formule générale [FexM1-x(btr)2(NCS)2]H2O où M = Zn, Co, Ni. En utilisant le modèle type-Ising, nous avons réussi à déterminer la distribution des paramètres physiques à partir des données FORC expérimentales. Nous avons aussi mis au point une procédure d analyse statistique de la distribution FORC obtenue. Dans une seconde étape, nous avons réalisé une extension dynamique de la méthode pour évaluer les effets cinétiques sur les cycles d hystérésis FORC photo-induits. Notre modèle a permis d ajuster les données expérimentales en utilisant comme paramètres d entrée la distribution obtenue à partir du cycle d hystérésis thermo-induit. Finalement nous sommes concentrés sur un problème d actualité qui est celui de la commutation induite par une perturbation rapide . Le dispositif de pression que nous avons automatisé, nous a permis de mesurer pour la première fois les diagrammes FORC pour l hystérésis piezo-induit. Par ailleurs nous avons aussi analysé la cinétique de commutation entre les états haut-spin et bas-spin sous l effet d une variation rapide de pression et de température.The main subject of this thesis is the investigation of the switching properties of the spin crossover compounds with the FORC (First Order Reversal Curves) method, only recently developed to characterise the magnetic materials, and translated by us to this field. Our work was split in three main directions. One of this was to applying the FORC method in order to study the thermal hysteresis of the compound with general formula [FexM1-x(btr)2(NCS)2]H2O where M = Zn, Co, Ni. Using an Ising-like model we had determined the distribution of physical parameters directly from experimental FORC data. A procedure of statistical analyses of the FORC distribution was also realized. The second direction was to evaluate the kinetic effects in the Light Induced Thermal Hysteresis (LITH) using the FORC diagram method. We have succeeded to fit the experimental data with our model using as input the physical distribution determined from thermal hysteresis. In the end we were focused on the actual problem of switching under a fast perturbation. The pressure set-up that we had automatized allowed us to measure for the first tine the FORCs for the pressure hysteresis. Also, under fast variation of pressure and temperature, the pizo and thermal stitching was measured and analysedVERSAILLES-BU Sciences et IUT (786462101) / SudocSudocFranceF

Cell type-specific YAP1-WWTR1/TAZ transcriptional responses after autophagy perturbations are determined by levels of α-catenins (CTNNA1 and CTNNA3).

The YAP1-WWTR1/TAZ transcription co-factors are key determinants of cell growth that are perturbed in many cancers. Previous studies have reported divergent responses in YAP1-WWTR1/TAZ activities after autophagy perturbations in different contexts. Recently, we identified that α-catenin levels determine whether YAP1-WWTR1/TAZ signaling will be increased or decreased after macroautophagy/autophagy inhibition/induction. CTNNA1/α-catenin can act as a switch in this pathway, as it is an autophagy substrate and a negative regulator of YAP1-WWTR1/TAZ. However, YAP1-WWTR1/TAZ are also directly degraded by autophagy and there is a feedback loop where YAP1-WWTR1/TAZ positively regulate autophagy. These features were integrated into a mathematical numerical model based on a set of differential equations in order to clarify the integrated output on YAP1-WWTR1/TAZ activity at different time-points after autophagy perturbation in cells with distinct initial levels of α-catenins (CTNNA1 and CTNNA3). Our theoretical and experimental data allow an understanding of cell-type specific and time-dependent responses to autophagy manipulations that may be relevant in many contexts, including different types of cancer.We are grateful for funding from the UK Dementia Research Institute (funded by MRC, Alzheimer’s Research UK and the Alzheimer’s Society) and The Roger de Spoelberch Foundation (D.C.R.), Wellcome Trust [095317/Z/11/Z, 100140/Z/12/Z], Romanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0733, within PNCDI-III (M.P.)

Unraveling the Environment Influence in Bistable Spin-Crossover Particles Using Magnetometric and Calorimetric First-Order Reverse Curves

International audienceA first-order reversal curve (FORC) method is used here to analyze the unexpected change of memory characteristic of spin-crossover microparticles embedded in glass-forming or semicrystalline matrices, reflected in the larger hysteresis loop compared to the bulk. The huge reversibility shown by the reversal curves was attributed to the effect of the matrix, implying a variable external pressure and a cutoff–switch on mechanism of particle–matrix interactions. The FORC analysis indicates that heating and cooling processes in the case of matrix-embedded spin-crossover systems are driven by different mechanisms. In complement of standard magnetometry measurements, a calorimetry method, which demands an alternative method to extract FORC distributions, is introduced for tracking the signature of the composite transformation to understand and control the role of embedding matrices

Unexpected Light-Induced Thermal Hysteresis in Matrix Embedded Low Cooperative Spin Crossover Microparticles

The embedding of spin-crossover micro- or nanocrystals in various surroundings dramatically changes their functionalities based on first-order spin transitions. The dampening of their internal cooperativity, together with introducing a new kind of interactions occurring at interfaces between spin-crossover particles and their environment, results in spectacular effects, as an enhanced hysteresis with non-cooperative transitions. In this work, we deal with the influence of the embedding matrix on the light-induced thermal hysteresis (LITH) in the case of spin-crossover microparticles of Fe(phen)2(NCS)2. Despite the low cooperativity of this compound, the competition between the continuous photoexcitation towards the metastable high spin state and the relaxation down to low spin ground state leads to a light-induced thermal hysteresis, with a quasi-static width of around 10 K. This unexpected hysteresis is explained by considering a switch-on/cutoff mechanism of the particle–matrix interactions in the framework of a mean-field approach based on negative external pressures, with Gaussian distributed variations and of an Ising-like model with various interactions with the environment. Additional first-order reversal curves measurements and corresponding calculated distributions are in line with relaxations under light and confirm the existence of a non-kinetic LITH

Mechanical-tuning of the cooperativity of SC particles via the matrix crystallization and related size effects

International audienceWe investigate the composites formed by a volume-changing material with a first-order spin transition [Fe-III(3-OMe-SalEen)(2)]PF6, when incorporated into a matrix of 1-butanol with a combination of calorimetric and magnetic measurements. DSC evidences the multiple phase transitions of the composite and the experimental conditions to select for promoting a possibly double phase transition of 1-butanol (crystallization) on both sides of the spin transition. Cycling the compound in the liquid matrix preserves the spin-transition properties of the reference with a 1 K wide hysteresis. In contrast, the crystallization around low-spin (high-spin) particles leads to changes in the heating (cooling) branch resulting in a non-persistent (persistent) hysteresis and a positive (negative) temperature shift, as a consequence of the environmental pressure experienced by the particles. The relaxed hysteretic regime that requires the crystallization of butanol around the high-spin particles of higher volume was studied by first-order reversal curves (FORCs) technique. The particular shape of FORCs shows a cooperative mechanism and the absence of the reversible component that was previously assigned to particles-matrix elastic interactions. The first-order spin transition of a single-crystal was characterized with X-ray diffraction measurements in presence of a thin layer of 1-butanol. The temperature dependence of the volume and unit-cell parameters reproduces the changes characterizing the matrix solidification around an ensemble of low-spin (butanol coating) or high-spin (paratone coating) particles. It is also shown that the increase of cooperativity resulting from the mechanical interactions taking place in the particle-matrix system can partly counterbalance the loss of cooperativity observed when reducing the size of the spin-transition materials

Multidrug-Resistant (MDR) Urinary Tract Infections Associated with Gut Microbiota in CoV and Non-CoV Patients in a Urological Clinic during the Pandemic: A Single Center Experience

The aim of the study was to compare the profile of COVID-19 (CoV)-infected patients with non-COVID-19 (non-CoV) patients who presented with a multidrug-resistant urinary tract infection (MDR UTI) associated with gut microbiota, as well as analyze the risk factors for their occurrence, the types of bacteria involved, and their spectrum of sensitivity. Methods: We conducted a case–control study on patients admitted to the urology clinic of the “Parhon” Teaching Hospital in Iasi, Romania, between March 2020 and August 2022. The study group consisted of 22 CoV patients with MDR urinary infections associated with gut microbiota. For the control group, 66 non-CoV patients who developed MDR urinary infections associated with gut microbiota were selected. Electronic medical records were analyzed to determine demographics, characteristics, and risk factors. The types of urinary tract bacteria involved in the occurrence of MDR urinary infections and their sensitivity spectrum were also analyzed. Results: Patients in both groups studied were over 60 years of age, with no differences in gender, environment of origin, and rate of comorbidities. Patients in the CoV group had a higher percentage of urosepsis (54.5% versus 21.2%, p p p > 0.05), antibiotic therapy (77.3% versus 87.9%, p > 0.05), and the presence of permanent urinary catheters (77.27% versus 84.85%, p > 0.05). Escherichia coli (31.8% versus 42.4%, p > 0.05), Klebsiella spp. (22.7% versus 34.8%, p > 0.05), and Pseudomonas aeruginosa (27.3% versus 9.1%, p > 0.05) were the most common urinary tract bacteria found in the etiology of MDR urinary infections in CoV and non-CoV patients. A high percentage of the involved MDR urinary tract bacteria were resistant to quinolones (71.4–76.2% versus 80.3–82%, p > 0.05) and cephalosporins (61.9–81% versus 63.9–83.6%, p > 0.05), both in CoV and non-CoV patients. Conclusions: Patients with urological interventions who remain on indwelling urinary catheters are at an increased risk of developing MDR urinary infections associated with gut microbiota resistant to quinolones and cephalosporins. Patients with MDR UTIs who have CoV-associated symptoms seem to have a higher rate of urosepsis and a longer hospitalization length