Suppressive might of a few: T follicular regulatory cells impede auto-reactivity despite being outnumbered in the germinal centres

The selection of high-affinity B cells and the production of high-affinity antibodies are mediated by T follicular helper cells (Tfhs) within germinal centres (GCs). Therein, somatic hypermutation and selection enhance B cell affinity but risk the emergence of self-reactive B cell clones. Despite being outnumbered compared to their helper counterpart, the ablation of T follicular regulatory cells (Tfrs) results in enhanced dissemination of self-reactive antibody-secreting cells (ASCs). The specific mechanisms by which Tfrs exert their regulatory action on self-reactive B cells are largely unknown. We developed computer simulations to investigate how Tfrs regulate either selection or differentiation of B cells to prevent auto-reactivity. We observed that Tfr-induced apoptosis of self-reactive B cells during the selection phase impedes self-reactivity with physiological Tfr numbers, especially when Tfrs can access centrocyte-enriched GC areas. While this aided in selecting non-self-reactive B cells by restraining competition, higher Tfr numbers distracted non-self-reactive B cells from receiving survival signals from Tfhs. Thus, the location and number of Tfrs must be regulated to circumvent such Tfr distraction and avoid disrupting GC evolution. In contrast, when Tfrs regulate differentiation of selected centrocytes by promoting recycling to the dark zone phenotype of self-reactive GC resident pre-plasma cells (GCPCs), higher Tfr numbers were required to impede the circulation of self-reactive ASCs (s–ASCs). On the other hand, Tfr-engagement with GCPCs and subsequent apoptosis of s–ASCs can control self-reactivity with low Tfr numbers, but does not confer selection advantage to non-self-reactive B cells. The simulations predict that to restrict auto-reactivity, natural redemption of self-reactive B cells is insufficient and that Tfrs should increase the mutation probability of self-reactive B cells

Changes in renal function after nephroureterectomy for upper urinary tract carcinoma: analysis of a large multicenter cohort (Radical Nephroureterectomy Outcomes (RaNeO) Research Consortium)

Purpose To investigate prevalence and predictors of renal function variation in a multicenter cohort treated with radical nephroureterectomy (RNU) for upper tract urothelial carcinoma (UTUC). Methods Patients from 17 tertiary centers were included. Renal function variation was evaluated at postoperative day (POD)-1, 6 and 12 months. Timepoints differences were Delta 1 = POD-1 eGFR - baseline eGFR; Delta 2 = 6 months eGFR - POD-1 eGFR; Delta 3 = 12 months eGFR - 6 months eGFR. We defined POD-1 acute kidney injury (AKI) as an increase in serum creatinine by >= 0.3 mg/dl or a 1.5 1.9-fold from baseline. Additionally, a cutoff of 60 ml/min in eGFR was considered to define renal function decline at 6 and 12 months. Logistic regression (LR) and linear mixed (LM) models were used to evaluate the association between clinical factors and eGFR decline and their interaction with follow-up. Results A total of 576 were included, of these 409(71.0%) and 403(70.0%) had an eGFR < 60 ml/min at 6 and 12 months, respectively, and 239(41.5%) developed POD-1 AKI. In multivariable LR analysis, age (Odds Ratio, OR 1.05, p < 0.001), male gender (OR 0.44, p = 0.003), POD-1 AKI (OR 2.88, p < 0.001) and preoperative eGFR < 60 ml/min (OR 7.58, p < 0.001) were predictors of renal function decline at 6 months. Age (OR 1.06, p < 0.001), coronary artery disease (OR 2.68, p = 0.007), POD-1 AKI (OR 1.83, p = 0.02), and preoperative eGFR < 60 ml/min (OR 7.80, p < 0.001) were predictors of renal function decline at 12 months. In LM models, age (p = 0.019), hydronephrosis (p < 0.001), POD-1 AKI (p < 0.001) and pT-stage (p = 0.001) influenced renal function variation (ss 9.2 +/- 0.7, p < 0.001) during follow-up. Conclusion Age, preoperative eGFR and POD-1 AKI are independent predictors of 6 and 12 months renal function decline after RNU for UTUC

Diagnosis of prostate cancer with magnetic resonance imaging in men treated with 5-alpha-reductase inhibitors

Purpose The primary aim of this study was to evaluate if exposure to 5-alpha-reductase inhibitors (5-ARIs) modifies the effect of MRI for the diagnosis of clinically significant Prostate Cancer (csPCa) (ISUP Gleason grade &gt;= 2).Methods This study is a multicenter cohort study including patients undergoing prostate biopsy and MRI at 24 institutions between 2013 and 2022. Multivariable analysis predicting csPCa with an interaction term between 5-ARIs and PIRADS score was performed. Sensitivity, specificity, and negative (NPV) and positive (PPV) predictive values of MRI were compared in treated and untreated patients.Results 705 patients (9%) were treated with 5-ARIs [median age 69 years, Interquartile range (IQR): 65, 73; median PSA 6.3 ng/ml, IQR 4.0, 9.0; median prostate volume 53 ml, IQR 40, 72] and 6913 were 5-ARIs naive (age 66 years, IQR 60, 71; PSA 6.5 ng/ml, IQR 4.8, 9.0; prostate volume 50 ml, IQR 37, 65). MRI showed PIRADS 1-2, 3, 4, and 5 lesions in 141 (20%), 158 (22%), 258 (37%), and 148 (21%) patients treated with 5-ARIs, and 878 (13%), 1764 (25%), 2948 (43%), and 1323 (19%) of untreated patients (p &lt; 0.0001). No difference was found in csPCa detection rates, but diagnosis of high-grade PCa (ISUP GG &gt;= 3) was higher in treated patients (23% vs 19%, p = 0.013). We did not find any evidence of interaction between PIRADS score and 5-ARIs exposure in predicting csPCa. Sensitivity, specificity, PPV, and NPV of PIRADS &gt;= 3 were 94%, 29%, 46%, and 88% in treated patients and 96%, 18%, 43%, and 88% in untreated patients, respectively.Conclusions Exposure to 5-ARIs does not affect the association of PIRADS score with csPCa. Higher rates of high-grade PCa were detected in treated patients, but most were clearly visible on MRI as PIRADS 4 and 5 lesions.Trial registration The present study was registered at ClinicalTrials.gov number: NCT05078359

In-silico-Analyse der Mechanismen, die die Funktionalität der Keimzentren regulieren - Fokus auf follikuläre regulatorische T-Zellen

The Germinal Center (GC) is a complex microanatomical structure that forms during a T cell-dependent antibody response. It provides the milieu for the maturation of B lymphocytes, achieved through iterative rounds of B cell proliferation, somatic hypermutation (SHM) of the B Cell Receptor (BCR), and clonal selection. The inherent randomness in the SHM process can cause the insertion of off-target mutations, which can lead to uncontrolled B cell proliferation or the production of autoreactive antibodies. The efficiency and safety of the B cell selection process within the GCs are regulated by Follicular T cells. Follicular Helper T (Tfh) cells promote the selection and expansion of B cells. Interaction with Tfh cells leads to c-Myc upregulation in B cells, defining positive selection and inducing dark zone proliferation. The latter continues by "inertia" after the loss of c-Myc expression, driven by the expression of cyclin D3 in a dose-dependent manner. In silico analysis supports a temporal sequence of cMyc⁺ subpopulations of selected B cells. Moreover, it helps quantify the loss of proliferative capacity in cells with cyclin D3 defects. Given the observed relevance of c-Myc and cyclin D3 mutations in lymphomas, these studies hold significant implications for unravelling lymphomagenesis. On the other hand, Follicular Regulatory T (Tfr) cells control the development of self-reactive PCs, which could trigger autoimmunity, but the mechanisms by which this is achieved remain incompletely understood. An agent-based model was developed to address this matter. The analysis considered the ratio of Tfh and Tfr cells number (Tfh:Tfr) and the localisation of Tfr cells within the GC. Simulation results suggest that an optimal Tfh:Tfr ratio is required for Tfr cells to effectively restrain the selection of self-reactive B cells through Tfr-induced apoptosis without hindering selection of non-self B cells. In contrast, simulations propose that if Tfr cells regulate the differentiation of B cells by promoting the recycling of self-reactive pre-PCs, self-reactive B cells would outcompete the non-self population. On the other hand, Tfr-induced apoptosis of self-reactive PCs can control self-reactivity with low Tfr numbers but does not confer a selection advantage to non-self-reactive B cells. The model could be a valuable tool for unraveling the impact of Tfr cells on the development of self-reactive antibodies and eventually gaining insight into how a skewed balance between Tfr and Tfh cells might lead to the development of autoimmunity.Das Keimzentrum (GC) ist eine komplexe mikroanatomische Struktur, die sich während einer T-Zell-abhängigen Antikörperantwort bildet. Es stellt das Milieu für die Reifung von B-Lymphozyten bereit, die durch iterative Runden der B-Zell-Proliferation, der somatischen Hypermutation (SHM) des B-Zell-Rezeptors (BCR) und der klonalen Selektion erreicht wird. Die inhärente Zufälligkeit des SHM-Prozesses kann dazu führen, dass Off-Target-Mutationen eingefügt werden, was zu einer unkontrollierten B-Zell-Proliferation oder der Produktion autoreaktiver Antikörper führen kann. Die Effizienz und Sicherheit des B-Zell-Selektionsprozesses innerhalb der GCs werden durch follikuläre T-Zellen reguliert. Follikuläre Helfer-T-Zellen (Tfh) fördern die Selektion und Expansion von B-Zellen. Die Interaktion mit Tfh-Zellen führt zu einer Hochregulierung von c-Myc in B-Zellen, was eine positive Selektion definiert und die Proliferation der dunklen Zone induziert. Letzteres setzt sich nach dem Verlust der c-Myc-Expression durch "Trägheit" fort, angetrieben durch die dosisabhängige Expression von Cyclin D3. Die In-silico-Analyse unterstützt eine zeitliche Abfolge von cMyc⁺-Subpopulationen ausgewählter B-Zellen. Darüber hinaus hilft es, den Verlust der Proliferationskapazität in Zellen mit Cyclin-D3-Defekten zu quantifizieren. Angesichts der beobachteten Relevanz von c-Myc- und Cyclin-D3-Mutationen bei Lymphomen haben diese Studien erhebliche Auswirkungen auf die Aufklärung der Lymphomentstehung. Andererseits steuern follikuläre regulatorische T-Zellen (Tfr) die Entwicklung selbstreaktiver PCs, die eine Autoimmunität auslösen könnten. Die Mechanismen, durch die dies erreicht wird, sind jedoch noch nicht vollständig verstanden. Um dieses Problem anzugehen, wurde ein agentenbasiertes Modell entwickelt. Bei der Analyse wurden das Verhältnis der Anzahl der Tfh- und Tfr-Zellen (Tfh:Tfr) und die Lokalisierung der Tfr-Zellen innerhalb des GC berücksichtigt. Simulationsergebnisse legen nahe, dass ein optimales Tfh:Tfr-Verhältnis für Tfr-Zellen erforderlich ist, um die Selektion selbstreaktiver B-Zellen durch Tfr-induzierte Apoptose wirksam einzuschränken, ohne die Selektion nicht-selbstaktiver B-Zellen zu behindern. Im Gegensatz dazu deuten Simulationen darauf hin, dass, wenn Tfr-Zellen die Differenzierung von B-Zellen regulieren, indem sie das Recycling selbstreaktiver Prä-PCs fördern, selbstreaktive B-Zellen die nicht-selbstaktive Population übertreffen würden. Andererseits kann die Tfr-induzierte Apoptose selbstreaktiver PCs die Selbstreaktivität bei niedrigen Tfr-Zahlen steuern, verleiht nicht selbstreaktiven B-Zellen jedoch keinen Selektionsvorteil. Das Modell könnte ein wertvolles Werkzeug sein, um den Einfluss von Tfr-Zellen auf die Entwicklung selbstreaktiver Antikörper aufzuklären und schließlich Erkenntnisse darüber zu gewinnen, wie ein gestörtes Gleichgewicht zwischen Tfr- und Tfh-Zellen zur Entwicklung von Autoimmunität führen könnte

DataSheet_1_Suppressive might of a few: T follicular regulatory cells impede auto-reactivity despite being outnumbered in the germinal centres.pdf

The selection of high-affinity B cells and the production of high-affinity antibodies are mediated by T follicular helper cells (Tfhs) within germinal centres (GCs). Therein, somatic hypermutation and selection enhance B cell affinity but risk the emergence of self-reactive B cell clones. Despite being outnumbered compared to their helper counterpart, the ablation of T follicular regulatory cells (Tfrs) results in enhanced dissemination of self-reactive antibody-secreting cells (ASCs). The specific mechanisms by which Tfrs exert their regulatory action on self-reactive B cells are largely unknown. We developed computer simulations to investigate how Tfrs regulate either selection or differentiation of B cells to prevent auto-reactivity. We observed that Tfr-induced apoptosis of self-reactive B cells during the selection phase impedes self-reactivity with physiological Tfr numbers, especially when Tfrs can access centrocyte-enriched GC areas. While this aided in selecting non-self-reactive B cells by restraining competition, higher Tfr numbers distracted non-self-reactive B cells from receiving survival signals from Tfhs. Thus, the location and number of Tfrs must be regulated to circumvent such Tfr distraction and avoid disrupting GC evolution. In contrast, when Tfrs regulate differentiation of selected centrocytes by promoting recycling to the dark zone phenotype of self-reactive GC resident pre-plasma cells (GCPCs), higher Tfr numbers were required to impede the circulation of self-reactive ASCs (s–ASCs). On the other hand, Tfr-engagement with GCPCs and subsequent apoptosis of s–ASCs can control self-reactivity with low Tfr numbers, but does not confer selection advantage to non-self-reactive B cells. The simulations predict that to restrict auto-reactivity, natural redemption of self-reactive B cells is insufficient and that Tfrs should increase the mutation probability of self-reactive B cells.</p

Development of the reproduction number from coronavirus SARS-CoV-2 case data in Germany and implications for political measures.

Background: SARS-CoV-2 has induced a worldwide pandemic and subsequent non-pharmaceutical interventions (NPIs) to control the spread of the virus. As in many countries, the SARS-CoV-2 pandemic in Germany has led to a consecutive roll-out of different NPIs. As these NPIs have (largely unknown) adverse effects, targeting them precisely and monitoring their effectiveness are essential. We developed a compartmental infection dynamics model with specific features of SARS-CoV-2 that allows daily estimation of a time-varying reproduction number and published this information openly since the beginning of April 2020. Here, we present the transmission dynamics in Germany over time to understand the effect of NPIs and allow adaptive forecasts of the epidemic progression. Methods: We used a data-driven estimation of the evolution of the reproduction number for viral spreading in Germany as well as in all its federal states using our model. Using parameter estimates from literature and, alternatively, with parameters derived from a fit to the initial phase of COVID-19 spread in different regions of Italy, the model was optimized to fit data from the Robert Koch Institute. Results: The time-varying reproduction number (Rt) in Germany decreased to <1 in early April 2020, 2-3 weeks after the implementation of NPIs. Partial release of NPIs both nationally and on federal state level correlated with moderate increases in Rt until August 2020. Implications of state-specific Rt on other states and on national level are characterized. Retrospective evaluation of the model shows excellent agreement with the data and usage of inpatient facilities well within the healthcare limit. While short-term predictions may work for a few weeks, long-term projections are complicated by unpredictable structural changes. Conclusions: The estimated fraction of immunized population by August 2020 warns of a renewed outbreak upon release of measures. A low detection rate prolongs the delay reaching a low case incidence number upon release, showing the importance of an effective testing-quarantine strategy. We show that real-time monitoring of transmission dynamics is important to evaluate the extent of the outbreak, short-term projections for the burden on the healthcare system, and their response to policy changes

New Antiandrogen Compounds Compared to Docetaxel in Metastatic Hormone Sensitive Prostate Cancer: Results from a Network Meta-Analysis

PURPOSE: Docetaxel represent the standard of care in patients with metastatic, hormone sensitive prostate cancer. However, androgen receptor axis targeted therapies have also been shown to be effective. We aimed to analyze findings in randomized controlled trials investigating first-line treatment for hormone sensitive prostate cancer. MATERIALS AND METHODS: We systematically reviewed the literature according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria and the PICO (Population, Intervention, Comparator, Outcomes) methodology. Outcomes of interest were overall and progression-free survival, and the rate of high grade adverse events. RESULTS: No treatment was superior to docetaxel in terms of overall survival. However, abiraterone (HR 0.89, 95% CI 0.76-1.05), enzalutamide (HR 0.90, 95% CI 0.69-1.19) and apalutamide (HR 0.90, 95% CI 0.67-1.22) showed nonstatistically significant lower overall mortality rates than docetaxel. Abiraterone (HR 0.71, 95% CI 0.59-0.86), enzalutamide (HR 0.61, 95% CI 0.49-0.75) and apalutamide (HR 0.74, 95% CI 0.57-0.95) also showed statistically significant lower disease progression rates than docetaxel. Furthermore, abiraterone (OR 0.83, 95% CI 0.56-1.21) showed no statistically significantly lower rate of high grade adverse events compared to docetaxel. Finally, enzalutamide (OR 0.56, 95% CI 0.35-0.92) and apalutamide (OR 0.44, 95% CI 0.24-0.79) showed statistically significantly lower rates of high grade adverse events compared to docetaxel. CONCLUSIONS: Treatment with androgen receptor axis targeted therapies combined with androgen deprivation therapy in patients with hormone sensitive prostate cancer did not offer a statistically significant advantage in overall survival compared to the standard, docetaxel. However, it was associated with a lower disease progression rate. Moreover, apalutamide and enzalutamide offer a better safety profile

Permissive selection followed by affinity-based proliferation of GC light zone B cells dictates cell fate and ensures clonal breadth.

Affinity maturation depends on how efficiently germinal centers (GCs) positively select B cells in the light zone (LZ). Positively selected GC B cells recirculate between LZs and dark zones (DZs) and ultimately differentiate into plasmablasts (PBs) and memory B cells (MBCs). Current understanding of the GC reaction presumes that cMyc-dependent positive selection of LZ B cells is a competitive affinity-dependent process; however, this cannot explain the production of GC-derived lower-affinity MBCs or retention of GC B cells with varied affinities. Here, by combining single-cell/bulk RNA sequencing and flow cytometry, we identified and characterized temporally and functionally distinct positively selected cMyc+ GC B cell subpopulations. cMyc+ LZ B cell subpopulations enriched with either higher- or lower-affinity cells diverged soon after permissive positive selection. The former subpopulation contained PB precursors, whereas the latter comprised less proliferative MBC precursors and future DZ entrants. The overall affinity of future DZ entrants was enhanced in the LZ through preferential proliferation of higher-affinity cells. Concurrently, lower-affinity cells were retained in GCs and protected from apoptosis. These findings redefine positive selection as a dynamic process generating three distinct B cell fates and elucidate how positive selection ensures clonal diversity for broad protection

Round-robin testing for LMO2 and MYC as immunohistochemical markers to screen MYC rearrangements in aggressive large B-cell lymphoma

Data de publicació electrònica: 27-06-2023Aggressive large B-cell lymphomas (aLBCL) include a heterogeneous group of lymphomas with diverse biological features. One of the approaches to the diagnosis of aLBCL is based on the identification of MYC rearrangements (MYC-R), in addition to BCL2 and BCL6 rearrangements by genetic techniques, mainly fluorescent in situ hybridization (FISH). Because of the low incidence of MYC-R, the identification of useful immunohistochemistry markers to select cases for MYC FISH testing may be useful in daily practice. In a previous work, we identified a strong association between the profile CD10 positive/LMO2 negative expression and the presence of MYC-R in aLBCL and obtained good intralaboratory reproducibility. In this study, we wanted to evaluate external reproducibility. To evaluate whether LMO2 can be a reproducible marker between observers 50 aLBCL cases were circulated among 7 hematopathologists of 5 hospitals. Fleiss' kappa index for LMO2 and MYC were 0.87 and 0.70, respectively, indicating high agreement between observers. In addition, during 2021-2022, the enrolled centers included LMO2 in their diagnostic panels to evaluate prospectively the utility of the marker, and 213 cases were analyzed. Comparing LMO2 with MYC, the group of CD10 positive cases showed higher specificity (86% vs 79%), positive predictive value (66% vs 58%), likelihood positive value (5.47 vs 3.78), and accuracy (83% vs 79%), whereas the negative predictive values remained similar (90% vs 91%). These findings place LMO2 as a useful and reproducible marker to screen MYC-R in aLBCL

Cyclin D3 drives inertial cell cycling in dark zone germinal center B cells

© 2020 Pae et al. During affinity maturation, germinal center (GC) B cells alternate between proliferation and somatic hypermutation in the dark zone (DZ) and affinity-dependent selection in the light zone (LZ). This anatomical segregation imposes that the vigorous proliferation that allows clonal expansion of positively selected GC B cells takes place ostensibly in the absence of the signals that triggered selection in the LZ, as if by "inertia."We find that such inertial cycles specifically require the cell cycle regulator cyclin D3. Cyclin D3 dose-dependently controls the extent to which B cells proliferate in the DZ and is essential for effective clonal expansion of GC B cells in response to strong T follicular helper (Tfh) cell help. Introduction into the Ccnd3 gene of a Burkitt lymphoma-associated gain-of-function mutation (T283A) leads to larger GCs with increased DZ proliferation and, in older mice, clonal B cell lymphoproliferation, suggesting that the DZ inertial cell cycle program can be coopted by B cells undergoing malignant transformation