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Objectives: In this study, we aimed to investigate the causes of liver test abnormalities in newly diagnosed patients naive to anti-tumoral therapy., Method: This study included a total of 490 patients with ALT levels > 5X ULN on liver function tests at the initial presentation to our clinic. Data from 247 (50.4%) patients diagnosed with cancer (cohort A) and 243 (49.6%) patients without cancer (cohort B) were compared with regard to the etiology of liver test abnormalities and the risk factors., Results: The most common etiological factor in cohort A was presence of liver metastasis (31.2%, n = 77). In the comparison of the two groups with regard to etiological factors; the rates of liver metastasis [31.2% vs 0%, ( p  < 0.001)], drug-induced liver toxicity [30/4% vs 19.8%, ( p  = 0.007)], pancreaticobiliary pathology [21.5% vs 14%, ( p  = 0.03)] and chronic viral hepatitis [14.2% vs 7.4%, ( p = 0.02)] were higher in the cohort A. The rate of NAFLD was higher in the cohort B [6.9% vs 42.2% ( p  < 0.001)., Conclusion: In our study, the most common cause of liver test abnormalities was the presence of liver metastasis in cohort A and NAFLD in cohort B.

Objective: To investigate the status of thiol-disulphide homeostasis and ischemic-modified albumin and their association with clinicopathological parameters in breast cancer., Study Design: A cross-sectional descriptive study., Place and Duration of Study: Department of Internal Medicine and Department of Medical Oncology, Dicle University, Turkey, from April to September 2021., Methodology: Forty treatment-naive female patients diagnosed with breast cancer who presented to the Oncology Clinic of the hospital and 33 healthy women with no comorbidities were included. Serum levels of native thiol (NT), disulphide (Ds), total thiol (TT), IMA (ischemic modified albumin) at diagnosis and disulphide/native thiol (Ds/NT), disulphide/total thiol (Ds/TT), and the ratios of native thiol/total thiol (NT/TT) were analysed by the colorimetric method., Results: Median age at diagnosis was 44 (29-70) years. The majority of patients had stage II-III disease (77.5%). Mean serum levels of TT were significantly lower in breast cancer patients (462.45 ± 100.2 μmol/L) compared to healthy controls (507.28 ± 75.72 μmol/L) (p=0.038). Mean serum levels of Ds were significantly lower in breast cancer patients (20.25 ± 5.94 μmol/L) compared to healthy controls (22.99 ± 3.56 μmol/L) (p=0.018). Meanwhile, mean IMA levels were significantly higher in breast cancer patients (0.81 ± 0.05 μmol/L) compared to healthy controls (0.73 ± 0.19 μmol/L) (p=0.016). NT and TT levels showed a moderate correlation with the percentage of fat mass and body mass index (BMI), and a weak correlation with age (p<0.05). Univariate and multivariate analyses examining the association between thiol-disulphide levels and patient clinical characteristics demonstrated that NT and TT levels had a statistically significant relationship with body mass index and menopausal status (p<0.05), with lower levels of NT and TT in postmenopausal patients and patients with high BMI., Conclusion: Decreased TT and Ds levels and increased IMA levels were determined in patients diagnosed with breast cancer compared to the healthy control group. Thiol-disulphide levels were observed to be associated with clinical characteristics such as menopausal status and BMI., Key Words: Breast cancer, Thiol, Ischemic modified albumin.

Objective: Cisplatin-paclitaxel and bevacizumab is a frequently used treatment regimen for metastatic or recurrent cervical cancer, and carboplatin-paclitaxel and bevacizumab are also among the recommended regimens. In this study we aimed to evaluate the efficacy of these two regimens for the treatment of metastatic or recurrent cervical cancer., Methods: Patients with metastatic or recurrent cervical cancer treated with cisplatin-paclitaxel and bevacizumab or carboplatin-paclitaxel and bevacizumab were retrospectively evaluated in this study. The clinical and demographic characteristics of patients in each group were evaluated. Median overall survival, progression-free survival, and response rates between the two groups were compared., Results: A total of 250 patients were included. Overall, the numbers of patients with recurrent disease and metastatic disease were 159 and 91, respectively. The most common histologic subtype was squamous cell carcinoma (83.2%). The median duration of follow-up was 13.6 (range 0.5-86) months. The median progression-free survival was 10.5 (95% CI 9.0 to 11.8) months in the cisplatin-paclitaxel and bevacizumab group (group 1), and 10.8 (95% CI 8.6 to 13.0) months in the carboplatin-paclitaxel and bevacizumab group (group 2) (HR 1.20; 95% CI 0.88 to 1.63; p=0.25). The median overall survival was 19.1 (95% CI 13.0 to 25.1) months in group 1 and 18.3 (95% CI 15.3 to 21.3) months in group 2 (HR 1.28; 95% CI 0.91 to 1.80; p=0.15)., Conclusions: There is no survival difference between cisplatin or carboplatin combined with paclitaxel and bevacizumab in metastatic or recurrent cervical cancer., Competing Interests: Competing interests: None declared., (© IGCS and ESGO 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: The aim of this study was to investigate the effect of the body fat mass ratio on survival and prognosis in advanced non-small-cell lung cancer patients., Methods: The study includes 200 patients who were diagnosed with advanced non-small-cell lung cancer between 2014 and 2018 and whose body fat mass percentage and body mass index (BMI) were determined using the Tanita Body Composition Analyzer during admission., Results: All patients had advanced incurable non-small-cell lung cancer (30% had locally advanced disease, 70% were stage IV). In the univariate and multivariate analyses, age, gender, histopathological type, smoking history, comorbidities, weight loss in the last six months and body mass index had no statistically significant effect on survival ( p  > 0.05). However, the performance status ( p  = 0.008), metastatic status ( p  = 0.003) and body fat mass ratio ( p  = 0.01) were found to have a significant effect on overall survival (OS): the median OS was 16.4 mo, in patients with the BFM ratio ≤ 22% and 29.2 mo, in those with > 22% ( p  = 0.01)., Conclusion: In this study, it was found that the body fat mass ratio was an important prognostic factor in patients with advanced non-small-cell lung cancer.

Objective: Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract. We aimed to examine the clinical characteristics and treatment outcomes of patients diagnosed with gastrointestinal stromal tumor (GIST) who were followed up and treated in our center., Methods: This study retrospectively evaluated the clinical characteristics, disease stages, administered treatments, and treatment responses of 67 patients diagnosed with GIST who presented to our center between 2007 and 2015., Results: Of the 67 patients included in our study, 24 (35.8%) were female and 43 (64.2%) were male. Median age at diagnosis was 54 years (23-86). Primary tumor localization was the stomach in 38.8% (n=26), small intestine in 46.2% (n=31), colorectal in 6% (n=4), and extra-gastrointestinal in 9% (n=6) of the patients. At diagnosis, 19 patients (28.4%) were at a metastatic stage. Fifty-seven patients (85.1%) underwent surgery. Thirty-three patients received one line, 20 patients received two lines, and 12 patients received three lines of treatment. The first-line treatment resulted in complete response in 12 patients (36.4%), partial response in 15 patients (45.5%), stable disease in 5 patients (15.2%), and progression in 1 patient (3%). Progression-free survival (PFS) was 36 months for the first-line treatment. The second-line treatment resulted in partial response in 7 patients (35%), stable disease in 12 patients (60%), and progression in 1 patient (5%). PFS was 12 months for the second-line treatment. The third-line treatment resulted in complete response in 1 patient (8.3%), partial response in 3 patients (25%), stable disease in 5 patients (41.7%), and progression in 3 patients (25%). PFS was 9 months for the third-line treatment. The fourth-line treatment resulted in stable disease in 4 patients (80%) and progression in 1 patient (20%). PFS was 4 months for the fourth-line treatment. Overall survival was 90 months for all patients., Conclusion: The use of tyrosine kinase inhibitors such as imatinib has a significant favorable effect on the prognosis in the treatment of GISTs, both in adjuvant therapy and in advanced stage disease., Competing Interests: Conflict of Interest: No conflict of interest was declared by the authors., (Copyright: © 2021 by Istanbul Northern Anatolian Association of Public Hospitals.)

Bariatric surgery has emerged as an effective treatment option in morbidly obese patients with non-alcoholic fatty liver disease (NAFLD). However, worsening or new onset of non-alcoholic steatohepatitis (NASH) and fibrosis have been observed. Caspase-cleaved keratin 18 (ccK18) has been established as a marker of hepatocyte apoptosis, a key event in NASH development. Thus, ccK18 measurements might be feasible to monitor bariatric surgery patients. Clinical data and laboratory parameters were collected from 39 patients undergoing laparoscopic Roux-en-Y gastric bypass at six timepoints, prior to surgery until one year after the procedure. ccK18 levels were measured and a high-throughput analysis of serum adipokines and cytokines was carried out. Half of the cohort's patients (20/39) presented with ccK18 levels indicative of progressed liver disease. 21% had a NAFLD-fibrosis score greater than 0.676, suggesting significant fibrosis. One year after surgery, a mean weight loss of 36.87% was achieved. Six and twelve months after surgery, ccK18 fragments were significantly reduced compared to preoperative levels ( p < 0.001). Yet nine patients did not show a decline in ccK18 levels ≥ 10% within one year postoperatively, which was considered a response to treatment. While no significant differences in laboratory parameters or ccK18 could be observed, they presented with a greater expression of leptin and fibrinogen before surgery. Consecutive ccK18 measurements monitored the resolution of NAFLD and identified non-responders to bariatric surgery with ongoing liver injury. Further studies are needed to elicit the pathological mechanisms in non-responders and study the potential of adipokines as prognostic markers.

DNA lesions inflicted by activation-induced deaminase (AID) instrumentally initiate the processes reshaping immunoglobulin genes in mature B-cells, from local somatic hypermutation (SHM) to junctions of distant breaks during class switch recombination (CSR). It remains incompletely understood how these divergent outcomes of AID attacks are differentially and temporally focused, with CSR strictly occurring in the Ig heavy chain (IgH) locus while SHM concentrates on rearranged V(D)J regions in the IgH and Ig light chain loci. In the IgH locus, disruption of either the 3'Regulatory Region (3'RR) super-enhancer or of switch (S) regions preceding constant genes, profoundly affects CSR. Reciprocally, we now examined if these elements are sufficient to induce CSR in a synthetic locus based on the Igκ locus backbone. Addition of a surrogate "core 3'RR" (c3'RR) and of a pair of transcribed and spliced Switch regions, together with a reporter system for "κ-CSR" yielded a switchable Igκ locus. While the c3'RR stimulated SHM at S regions, it also lowered the local SHM threshold necessary for switch recombination to occur. The 3'RR thus both helps recruit AID to initiate DNA lesions, but then also promotes their resolution through long-distance synapses and recombination following double-strand breaks., Competing Interests: The authors have declared that no competing interests exist.

Light chain (LC) deposition disease (LCDD) is a rare disorder characterized by glomerular and peritubular amorphous deposits of a monoclonal immunoglobulin LC, leading to nodular glomerulosclerosis and nephrotic syndrome. We developed a transgenic model using site-directed insertion of the variable domain of a pathogenic human LC gene into the mouse immunoglobulin κ locus, ensuring its production by all plasma cells (PCs). High free LC levels were achieved after backcrossing with mice presenting increased PC differentiation and no immunoglobulin heavy chain production. Our mouse model recapitulates the characteristic features of LCDD, including progressive glomerulosclerosis, nephrotic-range proteinuria, and finally kidney failure. The variable domain of the LC bears alone the structural properties involved in its pathogenicity. RNA sequencing conducted on PCs demonstrated that LCDD LC induces endoplasmic reticulum stress, likely accounting for the high efficiency of proteasome inhibitor-based therapy. Accordingly, reduction of circulating pathogenic LC was efficiently achieved and not only preserved renal function but also partially reversed kidney lesions. Finally, transcriptome analysis of presclerotic glomeruli revealed that proliferation and extracellular matrix remodeling represented the first steps of glomerulosclerosis, paving the way for future therapeutic strategies in LCDD and other kidney diseases featuring diffuse glomerulosclerosis, particularly diabetic nephropathy., (© 2020 by The American Society of Hematology.)

Purpose: This study aimed to analyze prognostic factors for survival and the reliability and the effectiveness of eribulin therapy in metastatic breast cancer (MBC) patients., Methods: A total of 80 patients treated with eribulin in 12 medical oncology centers in Turkey between 2013-2017 were retrospectively evaluated. Sixteen potential prognostic variables were assessed for analysis., Results: The patients had received a median of 5 prior chemotherapy regimens and a median of 3 eribulin cycles for MBC. Median progression-free survival (PFS) was 5.5 months (95% Cl: 4.1-7.8) and median overall survival (OS) was 11 months (95 % Cl: 6-15). Multivariate analysis showed that eribulin treatment line was shown to have independent prognostic significance for PFS. PFS difference was demostrated in patients who received 3 chemotherapy lines for advanced disease compared to those who had more than 3 chemotherapy lines [median PFS; 3 lines: 8.6 months (6.2-11) and ˃3 lines: 4.6 months (3.7-4.6) p=0.00]. The clinical benefit rate (CBR) was 52.5 and 35% in patients treated with three lines and with ˃3 previous chemotherapeutic regimens. Most common toxicities were neutropenia (62.5%), fatigue (52.5%), alopecia (50%) and nausea (37.5%)., Conclusions: Eribulin treatment line was identified as indepedent prognostic factor for PFS in MBC patients.

Rare tumours of the testis includes a wide variety of tumours. We aim to present clinical and histological characteristics of our patients with rare tumours of the testis. The medical records of 33 patients who were treated and followed-up for testicular rare tumours in our center between 2007 and 2020 were retrospectively reviewed. Of all the 243 testicular tumours, 222 cases (91.4%) were germ cell tumours and 21 cases (8.6%) were non-germ cell tumours. Thirty-three rare tumours of the testis including rare germ cell tumours and non-germ cell tumours were detected. The mean age of the patients at diagnosis was 34 years (range 18-68 years). The histological types of rare testicular tumours were as follows: teratoma 4.5% (n=11), sex-cord stromal tumours 4.5% (n=11), paratesticular tumours 3.2% (n=8), and the others [lymphoma 0.4% (n=1), mesothelioma 0.4% (n=1) and choriocarcinoma 0.4% (n=1)]. The median duration of follow-up was 32 months (range 1 to 256 months). None of the patients with non-metastatic disease stage developed recurrence after having received appropriate therapy. Metastatic disease was documented in 9 cases at the time of diagnosis (five patients with teratomas, two patients with Leydig cell tumour, one patient with choriocarcinoma and rhabdomyosarcoma). The most common subtypes of testicular rare tumours in our center was teratoma and sex-cord stromal tumours. Because of testicular rare tumours have different biological features and different clinical outcomes, the management of each tumour requires a different approach.

Purpose: This study aimed to analyze prognostic factors for survival and the reliability and the effectiveness of eribulin therapy in metastatic breast cancer (MBC) patients., Methods: A total of 80 patients treated with eribulin in 12 medical oncology centers in Turkey between 2013-2017 were retrospectively evaluated. Sixteen potential prognostic variables were assessed for analysis., Results: The patients had received a median of 5 prior chemotherapy regimens and a median of 3 eribulin cycles for MBC. Median progression-free survival (PFS) was 5.5 months (95% Cl: 4.1-7.8) and median overall survival (OS) was 11 months (95 % Cl: 6-15). Multivariate analysis showed that eribulin treatment line was shown to have independent prognostic significance for PFS. PFS difference was demostrated in patients who received 3 chemotherapy lines for advanced disease compared to those who had more than 3 chemotherapy lines [median PFS; 3 lines: 8.6 months (6.2-11) and ˃3 lines: 4.6 months (3.7-4.6) p=0.00]. The clinical benefit rate (CBR) was 52.5 and 35% in patients treated with three lines and with ˃3 previous chemotherapeutic regimens. Most common toxicities were neutropenia (62.5%), fatigue (52.5%), alopecia (50%) and nausea (37.5%)., Conclusions: Eribulin treatment line was identified as indepedent prognostic factor for PFS in MBC patients.

Purpose: To analyze the reliability and the effectiveness of chemotherapy and prognostic factors for survival in patients with HER2 (human epidermal growth receptor 2) negative early-stage breast cancer treated with adjuvant sequential anthracycline-based chemotherapy and paclitaxel., Methods: This analysis retrospectively evaluated the medical records of 756 HER2 negative early-stage breast cancer patients who received adjuvant sequential anthracycline-based chemotherapy and weekly paclitaxel in 15 medical oncology centers in Turkey between 2008-2015. Estrogen receptor (ER), progesterone receptor (PR),HER2,age,tumor size and grade,nodal status,perineural and lymphatic invasion,disease-free survival (DFS) and overall survival (OS) were analyzed., Results: The median patient age was 50 years (22-82). Median follow up period was 46 months (13-82). The rates of recurrence and death detected in this period were 14.8% and 7.4%, respectively. Median OS and PFS were not reached in this period. Five-year DFS and OS rates were 87% and 89%, respectively. Age (OR:0.35,95%Cl 0.12-0.96, p=0.04), PR status (OR:0.44,95%Cl 0.18-1, p=0.05), lymphatic invasion (OR:2.6,95%Cl 0.97-7.4, p=0.05) were independent prognostic factors. Most common grade 3-4 toxicities were fatigue (6.7%), neutropenia (1.7%) and nausea (1.3%). Neutropenic fever developed in 1.8% of the patients and peripheral neuropathy in 16.9%. Dose reduction was necessary for 10% of the patients due to grade 3-4 toxicity, whereas postponement of chemotherapy was necessary for 7% of the patients., Conclusions: This multicentric retrospective study confirmed that sequential adjuvant therapy with anthracycline-based chemotherapy and paclitaxel for HER2 negative breast cancer is an effective and reliable regimen.

Class switch recombination (CSR) plays an important role in adaptive immune response by enabling mature B cells to switch from IgM expression to the expression of downstream isotypes. CSR is preceded by inducible germline (GL) transcription of the constant genes and is controlled by the 3' regulatory region (3'RR) in a stimulus-dependent manner. Why the 3'RR-mediated up-regulation of GL transcription is delayed to the mature B-cell stage is presently unknown. Here we show that mice devoid of an inducible CTCF binding element, located in the α constant gene, display a marked isotype-specific increase of GL transcription in developing and resting splenic B cells and altered CSR in activated B cells. Moreover, insertion of a GL promoter downstream of the CTCF insulator led to premature activation of the ectopic promoter. This study provides functional evidence that the 3'RR has a developmentally controlled potential to constitutively activate GL promoters but that this activity is delayed, at least in part, by the CTCF insulator, which borders a transcriptionally active domain established by the 3'RR in developing B cells., Competing Interests: The authors declare no conflict of interest.

Cis-regulatory elements feature clustered sites for transcription factors, defining core enhancers and have inter-species homology. The mouse IgH 3΄ regulatory region (3'RR), a major B-cell super-enhancer, consists of four of such core enhancers, scattered throughout more than 25 kb of packaging 'junk DNA', the sequence of which is not conserved but follows a unique palindromic architecture which is conserved in all mammalian species. The 3'RR promotes long-range interactions and potential IgH loops with upstream promoters, controlling class switch recombination (CSR) and somatic hypermutation (SHM). It was thus of interest to determine whether this functional architecture also involves the specific functional structure of the super-enhancer itself, potentially promoted by its symmetric DNA shell. Since many transgenic 3'RR models simply linked core enhancers without this shell, it was also important to compare such a 'core 3'RR' (c3'RR) with the intact full-length super-enhancer in an actual endogenous IgH context. Packaging DNA between 3'RR core enhancers proved in fact to be necessary for optimal SHM, CSR and IgH locus expression in plasma cells. This reveals that packaging DNA can matter in the functional anatomy of a super-enhancer, and that precise evaluation of such elements requires full consideration of their global architecture., (© The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Mucosal HIV-1-specific IgA have been described as being able to neutralize HIV-1 and to block viral transcytosis. In serum and saliva, the anti-HIV IgA response is predominantly raised against the envelope of HIV-1. In this work, we describe the in vivo generation of gp41-specific IgA1 in humanized α1KI mice to produce chimeric IgA1. Mice were immunized with a conformational immunogenic gp41-transfected cell line. Among 2300 clones screened by immunofluorescence microscopy, six different gp41-specific IgA with strong recognition of gp41 were identified. Two of them have strong neutralizing activity against primary HIV-1 tier 1, 2, and 3 strains and present a low rate of somatic mutations and autoreactivity, unlike what was described for classical gp41-specific IgG. Epitopes were identified and located in the hepted repeat 2/membrane proximal external region. These Abs could be of interest in prophylactic treatment to block HIV-1 penetration in mucosa or in chronically infected patients in combination with antiretroviral therapy to reduce viral load and reservoir., (Copyright © 2016 by The American Association of Immunologists, Inc.)

IgA1 mesangial deposition is the hallmark of IgA nephropathy and Henoch-Schönlein purpura, the onset of which often follows infections. Deposited IgA has been reported as polymeric, J chain associated, and often, hypogalactosylated but with no information concerning the influence of the IgA repertoire or the link between immune stimuli and IgA structure. We explored these issues in the α1KI mouse model, which produces polyclonal human IgA1 prone to mesangial deposition. Compared with mice challenged by a conventional environment, mice in a specific pathogen-free environment had less IgA deposition. However, serum IgA of specific pathogen-free mice showed more galactosylation and much lower polymerization. Notably, wild-type, α1KI, and even J chain-deficient mice showed increased polymeric serum IgA on exposure to pathogens. Strict germfree conditions delayed but did not completely prevent deposition; mice housed in these conditions had very low serum IgA levels and produced essentially monomeric IgA. Finally, comparing monoclonal IgA1 that had different variable regions and mesangial deposition patterns indicated that, independently of glycosylation and polymerization, deposition might also depend on IgA carrying specific variable domains. Together with IgA quantities and constant region post-translational modifications, repertoire changes during immune responses might, thus, modulate IgA propensity to deposition. These IgA features are not associated with circulating immune complexes and C3 deposition and are more pertinent to an initial IgA deposition step preceding overt clinical symptoms in patients., (Copyright © 2016 by the American Society of Nephrology.)

The IgH 3' regulatory region (3'RR) controls class switch recombination (CSR) and somatic hypermutation (SHM) in B cells. The mouse 3'RR contains four enhancer elements with hs1,2 flanked by inverted repeated sequences and the centre of a 25-kb palindrome bounded by two hs3 enhancer inverted copies (hs3a and hs3b). hs4 lies downstream of the palindrome. In mammals, evolution maintained this unique palindromic arrangement, suggesting that it is functionally significant. Here we report that deconstructing the palindromic IgH 3'RR strongly affects its function even when enhancers are preserved. CSR and IgH transcription appear to be poorly dependent on the 3'RR architecture and it is more or less preserved, provided 3'RR enhancers are present. By contrast, a 'palindromic effect' significantly lowers VH germline transcription, AID recruitment and SHM. In conclusion, this work indicates that the IgH 3'RR does not simply pile up enhancer units but also optimally exposes them into a functional architecture of crucial importance.

As a master regulator of functional Ig heavy chain (IgH) expression, the IgH 3' regulatory region (3'RR) controls multiple transcription events at various stages of B-cell ontogeny, from newly formed B cells until the ultimate plasma cell stage. The IgH 3'RR plays a pivotal role in early B-cell receptor expression, germ-line transcription preceding class switch recombination, interactions between targeted switch (S) regions, variable region transcription before somatic hypermutation, and antibody heavy chain production, but the functional ranking of its different elements is still inaccurate, especially that of its evolutionarily conserved quasi-palindromic structure. By comparing relevant previous knockout (KO) mouse models (3'RR KO and hs3b-4 KO) to a novel mutant devoid of the 3'RR quasi-palindromic region (3'PAL KO), we pinpointed common features and differences that specify two distinct regulatory entities acting sequentially during B-cell ontogeny. Independently of exogenous antigens, the 3'RR distal part, including hs4, fine-tuned B-cell receptor expression in newly formed and naïve B-cell subsets. At mature stages, the 3'RR portion including the quasi-palindrome dictated antigen-dependent locus remodeling (global somatic hypermutation and class switch recombination to major isotypes) in activated B cells and antibody production in plasma cells.

Aberrantly rearranged immunoglobulin (Ig) alleles are frequent. They are usually considered sterile and innocuous as a result of nonsense-mediated mRNA decay. However, alternative splicing can yield internally deleted proteins from such nonproductively V(D)J-rearranged loci. We show that nonsense codons from variable (V) Igκ exons promote exon-skipping and synthesis of V domain-less κ light chains (ΔV-κLCs). Unexpectedly, such ΔV-κLCs inhibit plasma cell (PC) differentiation. Accordingly, in wild-type mice, rearrangements encoding ΔV-κLCs are rare in PCs, but frequent in B cells. Likewise, enforcing expression of ΔV-κLCs impaired PC differentiation and antibody responses without disturbing germinal center reactions. In addition, PCs expressing ΔV-κLCs synthesize low levels of Ig and are mostly found among short-lived plasmablasts. ΔV-κLCs have intrinsic toxic effects in PCs unrelated to Ig assembly, but mediated by ER stress-associated apoptosis, making PCs producing ΔV-κLCs highly sensitive to proteasome inhibitors. Altogether, these findings demonstrate a quality control checkpoint blunting terminal PC differentiation by eliminating those cells expressing nonfunctionally rearranged Igκ alleles. This truncated Ig exclusion (TIE) checkpoint ablates PC clones with ΔV-κLCs production and exacerbated ER stress response. The TIE checkpoint thus mediates selection of long-lived PCs with limited ER stress supporting high Ig secretion, but with a cost in terms of antigen-independent narrowing of the repertoire., (© 2016 Srour et al.)

Developing lymphocytes somatically diversify their antigen-receptor loci through V(D)J recombination. The process is associated with allelic exclusion, which results in monoallelic expression of an antigen receptor locus. Various cis-regulatory elements control V(D)J recombination in a developmentally regulated manner, but their role in allelic exclusion is still unclear. At the immunoglobulin heavy chain locus (IgH), the Eμ enhancer plays a critical role in V(D)J recombination. We generated a mouse line with a replacement mutation in the constant region of the locus that duplicates the Eμ enhancer and allows premature expression of the γ3 heavy chain. Strikingly, IgM expression was completely and specifically excluded in cis from the mutant allele. This cis exclusion recapitulated the main features of allelic exclusion, including differential exclusion of variable genes. Notably, sense and antisense transcription within the distal variable domain and distal V(H)-DJ(H) recombination were inhibited. cis exclusion was established and stably maintained despite an active endogenous Eμ enhancer. The data reveal the importance of the dynamic, developmental stage-dependent interplay between IgH locus enhancers and signaling in the induction and maintenance of allelic exclusion.

B-cell terminal differentiation into antibody secreting plasma cells (PCs) features a transcriptional shift driven by the activation of plasma cell lineage determinants such as Blimp-1 and Xbp-1, together with the extinction of Pax5. Little is known about the signals inducing this change in transcriptional networks and the role of the B-cell receptor (BCR) in terminal differentiation remains especially controversial. Here, we show that tonic BCR signal strength influences PC commitment in vivo. Using immuno-globulin light chain transgenic mice expressing suboptimal surface BCR levels and latent membrane protein 2A knock-in animals with defined BCR-like signal strengths, we show that weak, antigen-independent constitutive BCR signaling facilitates spontaneous PC differentiation in vivo and in vitro in response to TLR agonists or CD40/IL-4. Conversely, increasing tonic signaling completely prevents this process that is rescued by lowering surface BCR expression or through the inhibition of Syk phosphorylation. These findings provide new insights into the role of basal BCR signaling in PC differentiation and point to the need to resolve a strong BCR signal in order to guarantee terminal differentiation., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Background: Henoch-Schönlein purpura (HSP) and IgA nephropathy (IgAN) are characterized by mesangial deposition of polyclonal IgA eventually showing aberrant glycosylation, affinity for mesangial cells and/or co-precipitation with antigen, bacterial peptides, autoantibodies or soluble receptors. IgA were also suggested to be negatively charged and predominantly of λ type but rarely in a monoclonal form., Methods: A gammopathy case with HSP provided us with a unique molecularly defined nephritogenic IgA1λ. Immunological analysis, biological activities, glycosylation analysis and finally IgA sequence were determined., Results: Compared to IgA1 from healthy subjects or IgAN patients, IgA1 CAT showed hyposialylation but no hypogalactosylation, in agreement with underexpression of sialyltransferase genes by the plasma cell clone. IgA variable domains had low pIs with negatively charged complementarity-determining regions. Weak reactivity appeared against the cationic autoantigen lactoferrin, which was, however, absent from kidney deposits. Deposition also occurred in mice upon injection of only the polymeric form of IgA1 CAT, despite whether or not co-injected with lactoferrin., Conclusions: This monoclonal model of IgA nephritogenicity strongly suggests that beside hinge region glycosylation, V domains play a role in IgA stability and pathogenicity and supports the hypothesis that responses against cationic epitopes from pathogens or autoantigens may select negatively charged complementarity-determining regions prone either to bind charged structures of the mesangium or to promote by themselves IgA aggregation and deposition.

Anemia because of insufficient production of and/or response to erythropoietin (Epo) is a major complication of chronic kidney disease and cancer. The mechanisms modulating the sensitivity of erythroblasts to Epo remain poorly understood. We show that, when cultured with Epo at suboptimal concentrations, the growth and clonogenic potential of erythroblasts was rescued by transferrin receptor 1 (TfR1)-bound polymeric IgA1 (pIgA1). Under homeostatic conditions, erythroblast numbers were increased in mice expressing human IgA1 compared to control mice. Hypoxic stress of these mice led to increased amounts of pIgA1 and erythroblast expansion. Expression of human IgA1 or treatment of wild-type mice with the TfR1 ligands pIgA1 or iron-loaded transferrin (Fe-Tf) accelerated recovery from acute anemia. TfR1 engagement by either pIgA1 or Fe-Tf increased cell sensitivity to Epo by inducing activation of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways. These cellular responses were mediated through the TfR1-internalization motif, YXXΦ. Our results show that pIgA1 and TfR1 are positive regulators of erythropoiesis in both physiological and pathological situations. Targeting this pathway may provide alternate approaches to the treatment of ineffective erythropoiesis and anemia.

Class switch recombination (CSR) occurs between highly repetitive sequences called switch (S) regions and is initiated by activation-induced cytidine deaminase (AID). CSR is preceded by a bidirectional transcription of S regions but the relative importance of sense and antisense transcription for CSR in vivo is unknown. We generated three mouse lines in which we attempted a premature termination of transcriptional elongation by inserting bidirectional transcription terminators upstream of Sμ, upstream of Sγ3 or downstream of Sγ3 sequences. The data show, at least for Sγ3, that sense transcriptional elongation across S region is absolutely required for CSR whereas its antisense counterpart is largely dispensable, strongly suggesting that sense transcription is sufficient for AID targeting to both DNA strands.

Class-switch recombination (CSR) enables IgM-producing B cells to switch to the production of IgG, IgE, and IgA. The process requires germ-line (GL) transcription that initiates from promoters upstream of switch (S) sequences and is regulated by the 3' regulatory region (3'RR) located downstream of the Ig heavy chain (IgH) locus. How the 3'RR effect its long-range activation is presently unclear. We generated a mouse line in which Igamma3 GL promoter was replaced by Igamma1. We found that GL transcription could initiate from the inserted Igamma1 promoter and was induced by increased concentrations of IL-4 and that the transcripts were normally spliced. However, when compared with GL transcripts derived from the endogenous Igamma1 promoter in the same stimulation conditions, those from the inserted Igamma1 promoter were less abundant. CSR to Cgamma3 was abrogated both in vivo and in vitro. The results strongly suggest that the endogenous Igamma1 promoter insulates the inserted Igamma1 from the long-range activating effect of the 3'RR. The implications of our findings are discussed in light of the prominent models of long-distance activation in complex loci.

The mechanism by which the cytidine deaminase activation-induced deaminase (AID) acts at immunoglobulin heavy-chain class switch regions during mammalian class switch recombination (CSR) remains unclear. R-loops have been proposed as a basis for this targeting. Here, we show that the difference between various forms of the Smu locus that can or cannot undergo CSR correlates well with the locations and detectability of R-loops. The Smu R-loops can initiate hundreds of base pairs upstream of the core repeat switch regions, and the area where the R-loops initiate corresponds to the zone where the AID mutation frequency begins to rise, despite a constant density of WRC sites in this region. The frequency of R-loops is 1 in 25 alleles, regardless of the presence of the core Smu repeats, again consistent with the initiation of most R-loops upstream of the core repeats. These findings explain the surprisingly high levels of residual CSR in B cells from mice lacking the core Smu repeats but the marked reduction in CSR in mice with deletions of the region upstream of the core Smu repeats. These studies also provide the first analysis of how R-loop formation in the eukaryotic chromosome depends on the DNA sequence.

Class switch recombination (CSR) is preceded by germ line transcription that initiates from promoters upstream of switch (S) sequences and terminates downstream of associated constant genes. Previous work showed that germ line transcripts and their processing are required for CSR and that germ line transcription is regulated in a major part by a regulatory region located downstream of the Ig heavy chain locus. This long-range, polarized effect can be disturbed by inserting an expressed neomycine resistance (neo(r)) gene. To contribute to a better understanding of the mechanism of such a long-distance regulation, we generated knock-in mice in which a neo(r) gene was inserted downstream of Igamma3 exon leaving intact all the necessary elements for germ line transcription and splicing. We show that the expressed neo(r) gene interferes with transcription initiation from Igamma3, and that it impairs but does not block S recombination to Cgamma3. Moreover, we show for the first time that the neo(r) gene provides through chimeric neo(r)-Cgamma3 transcripts the necessary elements for splicing of germ line transcripts by activating two novel cryptic splice sites, one in the coding region of the intronless neo(r) gene and the other in the Igamma3-Cgamma3 intron.

Immunoglobulin heavy-chain class-switch recombination (CSR) occurs between highly repetitive switch sequences located upstream of the constant region genes. However, the role of these sequences remains unclear. Mutant mice were generated in which most of the I mu -- C mu intron was deleted, including all the repeats. Late B-cell development was characterized by a severe impairment, but not a complete block, in class switching to all isotypes despite normal germ line transcription. Sequence analysis of the I mu -- C mu intron in in vitro activated-mutant splenocytes did not reveal any significant increase in activation-induced cytidine deaminase (AID)-induced somatic mutations. Analysis of switch junctions showed that, in the absence of any S mu repeat, the Imicro exon was readily used as a substrate for CSR. In contrast to the sequence alterations downstream of the switch junctions, very few, if any, mutations were found upstream of the junction sites. Our data suggest that the core E mu enhancer could be the boundary for CSR-associated somatic mutations. We propose that the core E mu enhancer plays a central role in the temporal dissociation of somatic hypermutation from class switching.