@article{DirksFischerHaaseetal.2021,
  author    = {Dirks, Johannes and Fischer, Jonas and Haase, Gabriele and Holl-Wieden, Annette and Hofmann, Christine and Girschick, Hermann and Morbach, Henner},
  title     = {CD21\(^{lo/-}\)CD27\(^-\)IgM\(^-\) Double-Negative B Cells Accumulate in the Joints of Patients With Antinuclear Antibody-Positive Juvenile Idiopathic Arthritis},
  series = {Frontiers in Pediatrics},
  volume    = {9},
  journal   = {Frontiers in Pediatrics},
  issn      = {2296-2360},
  doi       = {10.3389/fped.2021.635815},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236286},
  year      = {2021},
  abstract  = {Juvenile idiopathic arthritis (JIA) encompasses a heterogeneous group of diseases. The appearance of antinuclear antibodies (ANAs) in almost half of the patients suggests B cell dysregulation as a distinct pathomechanism in these patients. Additionally, ANAs were considered potential biomarkers encompassing a clinically homogenous subgroup of JIA patients. However, in ANA+ JIA patients, the site of dysregulated B cell activation as well as the B cell subsets involved in this process is still unknown. Hence, in this cross-sectional study, we aimed in an explorative approach at characterizing potential divergences in B cell differentiation in ANA+ JIA patients by assessing the distribution of peripheral blood (PB) and synovial fluid (SF) B cell subpopulations using flow cytometry. The frequency of transitional as well as switched-memory B cells was higher in PB of JIA patients than in healthy controls. There were no differences in the distribution of B cell subsets between ANA- and ANA+ patients in PB. However, the composition of SF B cells was different between ANA- and ANA+ patients with increased frequencies of CD21\(^{lo/-}\)CD27\(^-\)IgM\(^-\) "double negative" (DN) B cells in the latter. DN B cells might be a characteristic subset expanding in the joints of ANA+ JIA patients and are potentially involved in the antinuclear immune response in these patients. The results of our explorative study might foster further research dissecting the pathogenesis of ANA+ JIA patients.},
  language  = {en}
}
@article{FischerDirksKlaussneretal.2022,
  author    = {Fischer, Jonas and Dirks, Johannes and Klaussner, Julia and Haase, Gabriele and Holl-Wieden, Annette and Hofmann, Christine and Hackenberg, Stephan and Girschick, Hermann and Morbach, Henner},
  title     = {Effect of clonally expanded PD-1\(^h\)\(^i\)\(^g\)\(^h\) CXCR5-CD4+ peripheral T Helper cells on B cell differentiation in the joints of patients with antinuclear antibody-positive juvenile idiopathic arthritis},
  series = {Arthritis \& Rheumatology},
  volume    = {74},
  journal   = {Arthritis \& Rheumatology},
  number    = {1},
  doi       = {10.1002/art.41913},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256607},
  pages     = {150-162},
  year      = {2022},
  abstract  = {Objective Antinuclear antibody (ANA)-positive juvenile idiopathic arthritis (JIA) is characterized by synovial B cell hyperactivity, but the precise role of CD4+ T cells in promoting local B cell activation is unknown. This study was undertaken to determine the phenotype and function of synovial CD4+ T cells that promote aberrant B cell activation in JIA. Methods Flow cytometry was performed to compare the phenotype and cytokine patterns of PD-1\(^h\)\(^i\)\(^g\)\(^h\)CD4+ T cells in the synovial fluid (SF) of patients with JIA and T follicular helper cells in the tonsils of control individuals. TCRVB next-generation sequencing was used to analyze T cell subsets for signs of clonal expansion. The functional impact of these T cell subsets on B cells was examined in cocultures in vitro. Results Multidimensional flow cytometry revealed the expansion of interleukin-21 (IL-21) and interferon-γ (IFNγ)-coexpressing PD-1\(^h\)\(^i\)\(^g\)\(^h\)CXCR5-HLA-DR+CD4+ T cells that accumulate in the joints of ANA-positive JIA patients. These T cells exhibited signs of clonal expansion with restricted T cell receptor clonotypes. The phenotype resembled peripheral T helper (Tph) cells with an extrafollicular chemokine receptor pattern and high T-bet and B lymphocyte-induced maturation protein 1 expression, but low B cell lymphoma 6 expression. SF Tph cells, by provision of IL-21 and IFNy, skewed B cell differentiation toward a CD21\(^l\)\(^o\)\(^w\)\(^/\)\(^-\)CD11c+ phenotype in vitro. Additionally, SF Tph cell frequencies correlated with the appearance of SF CD21\(^l\)\(^o\)\(^w\)\(^/\)\(^-\)CD11c+CD27-IgM- double-negative (DN) B cells in situ.},
  language  = {en}
}
@article{DirksHaaseCantaertetal.2022,
  author    = {Dirks, Johannes and Haase, Gabriele and Cantaert, Tineke and Frey, Lea and Klaas, Moritz and Rickert, Christian H. and Girschick, Hermann and Meffre, Eric and Morbach, Henner},
  title     = {A novel AICDA splice-site mutation in two siblings with HIGM2 permits somatic hypermutation but abrogates mutational targeting},
  series = {Journal of Clinical Immunology},
  volume    = {42},
  journal   = {Journal of Clinical Immunology},
  number    = {4},
  doi       = {10.1007/s10875-022-01233-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324253},
  pages     = {771-782},
  year      = {2022},
  abstract  = {Hyper-IgM syndrome type 2 (HIGM2) is a B cell intrinsic primary immunodeficiency caused by mutations in AICDA encoding activation-induced cytidine deaminase (AID) which impair immunoglobulin class switch recombination (CSR) and somatic hypermutation (SHM). Whereas autosomal-recessive AID-deficiency (AR-AID) affects both CSR and SHM, the autosomal-dominant form (AD-AID) due to C-terminal heterozygous variants completely abolishes CSR but only partially affects SHM. AR-AID patients display enhanced germinal center (GC) reactions and autoimmune manifestations, which are not present in AD-AID, suggesting that SHM but not CSR regulates GC reactions and peripheral B cell tolerance. Herein, we describe two siblings with HIGM2 due to a novel homozygous AICDA mutation (c.428-1G > T) which disrupts the splice acceptor site of exon 4 and results in the sole expression of a truncated AID variant that lacks 10 highly conserved amino acids encoded by exon 4 (AID-ΔE4a). AID-ΔE4a patients suffered from defective CSR and enhanced GC reactions and were therefore indistinguishable from other AR-AID patients. However, the AID-ΔE4a variant only partially affected SHM as observed in AD-AID patients. In addition, AID-ΔE4a but not AD-AID patients revealed impaired targeting of mutational hotspot motives and distorted mutational patterns. Hence, qualitative defects in AID function and altered SHM rather than global decreased SHM activity may account for the disease phenotype in these patients.},
  language  = {en}
}
@article{ElHelouBiegnerBodeetal.2019,
  author    = {El-Helou, Sabine M. and Biegner, Anika-Kerstin and Bode, Sebastian and Ehl, Stephan R. and Heeg, Maximilian and Maccari, Maria E. and Ritterbusch, Henrike and Speckmann, Carsten and Rusch, Stephan and Scheible, Raphael and Warnatz, Klaus and Atschekzei, Faranaz and Beider, Renata and Ernst, Diana and Gerschmann, Stev and Jablonka, Alexandra and Mielke, Gudrun and Schmidt, Reinhold E. and Sch{\"u}rmann, Gesine and Sogkas, Georgios and Baumann, Ulrich H. and Klemann, Christian and Viemann, Dorothee and Bernuth, Horst von and Kr{\"u}ger, Renate and Hanitsch, Leif G. and Scheibenbogen, Carmen M. and Wittke, Kirsten and Albert, Michael H. and Eichinger, Anna and Hauck, Fabian and Klein, Christoph and Rack-Hoch, Anita and Sollinger, Franz M. and Avila, Anne and Borte, Michael and Borte, Stephan and Fasshauer, Maria and Hauenherm, Anja and Kellner, Nils and M{\"u}ller, Anna H. and {\"U}lzen, Anett and Bader, Peter and Bakhtiar, Shahrzad and Lee, Jae-Yun and Heß, Ursula and Schubert, Ralf and W{\"o}lke, Sandra and Zielen, Stefan and Ghosh, Sujal and Laws, Hans-Juergen and Neubert, Jennifer and Oommen, Prasad T. and H{\"o}nig, Manfred and Schulz, Ansgar and Steinmann, Sandra and Klaus, Schwarz and D{\"u}ckers, Gregor and Lamers, Beate and Langemeyer, Vanessa and Niehues, Tim and Shai, Sonu and Graf, Dagmar and M{\"u}glich, Carmen and Schmalzing, Marc T. and Schwaneck, Eva C. and Tony, Hans-Peter and Dirks, Johannes and Haase, Gabriele and Liese, Johannes G. and Morbach, Henner and Foell, Dirk and Hellige, Antje and Wittkowski, Helmut and Masjosthusmann, Katja and Mohr, Michael and Geberzahn, Linda and Hedrich, Christian M. and M{\"u}ller, Christiane and R{\"o}sen-Wolff, Angela and Roesler, Joachim and Zimmermann, Antje and Behrends, Uta and Rieber, Nikolaus and Schauer, Uwe and Handgretinger, Rupert and Holzer, Ursula and Henes, J{\"o}rg and Kanz, Lothar and Boesecke, Christoph and Rockstroh, J{\"u}rgen K. and Schwarze-Zander, Carolynne and Wasmuth, Jan-Christian and Dilloo, Dagmar and H{\"u}lsmann, Brigitte and Sch{\"o}nberger, Stefan and Schreiber, Stefan and Zeuner, Rainald and Ankermann, Tobias and Bismarck, Philipp von and Huppertz, Hans-Iko and Kaiser-Labusch, Petra and Greil, Johann and Jakoby, Donate and Kulozik, Andreas E. and Metzler, Markus and Naumann-Bartsch, Nora and Sobik, Bettina and Graf, Norbert and Heine, Sabine and Kobbe, Robin and Lehmberg, Kai and M{\"u}ller, Ingo and Herrmann, Friedrich and Horneff, Gerd and Klein, Ariane and Peitz, Joachim and Schmidt, Nadine and Bielack, Stefan and Groß-Wieltsch, Ute and Classen, Carl F. and Klasen, Jessica and Deutz, Peter and Kamitz, Dirk and Lassy, Lisa and Tenbrock, Klaus and Wagner, Norbert and Bernbeck, Benedikt and Brummel, Bastian and Lara-Villacanas, Eusebia and M{\"u}nstermann, Esther and Schneider, Dominik T. and Tietsch, Nadine and Westkemper, Marco and Weiß, Michael and Kramm, Christof and K{\"u}hnle, Ingrid and Kullmann, Silke and Girschick, Hermann and Specker, Christof and Vinnemeier-Laubenthal, Elisabeth and Haenicke, Henriette and Schulz, Claudia and Schweigerer, Lothar and M{\"u}ller, Thomas G. and Stiefel, Martina and Belohradsky, Bernd H. and Soetedjo, Veronika and Kindle, Gerhard and Grimbacher, Bodo},
  title     = {The German national registry of primary immunodeficiencies (2012-2017)},
  series = {Frontiers in Immunology},
  volume    = {10},
  journal   = {Frontiers in Immunology},
  doi       = {10.3389/fimmu.2019.01272},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226629},
  year      = {2019},
  abstract  = {Introduction: The German PID-NET registry was founded in 2009, serving as the first national registry of patients with primary immunodeficiencies (PID) in Germany. It is part of the European Society for Immunodeficiencies (ESID) registry. The primary purpose of the registry is to gather data on the epidemiology, diagnostic delay, diagnosis, and treatment of PIDs. Methods: Clinical and laboratory data was collected from 2,453 patients from 36 German PID centres in an online registry. Data was analysed with the software Stata® and Excel. Results: The minimum prevalence of PID in Germany is 2.72 per 100,000 inhabitants. Among patients aged 1-25, there was a clear predominance of males. The median age of living patients ranged between 7 and 40 years, depending on the respective PID. Predominantly antibody disorders were the most prevalent group with 57\% of all 2,453 PID patients (including 728 CVID patients). A gene defect was identified in 36\% of patients. Familial cases were observed in 21\% of patients. The age of onset for presenting symptoms ranged from birth to late adulthood (range 0-88 years). Presenting symptoms comprised infections (74\%) and immune dysregulation (22\%). Ninety-three patients were diagnosed without prior clinical symptoms. Regarding the general and clinical diagnostic delay, no PID had undergone a slight decrease within the last decade. However, both, SCID and hyper IgE-syndrome showed a substantial improvement in shortening the time between onset of symptoms and genetic diagnosis. Regarding treatment, 49\% of all patients received immunoglobulin G (IgG) substitution (70\%-subcutaneous; 29\%-intravenous; 1\%-unknown). Three-hundred patients underwent at least one hematopoietic stem cell transplantation (HSCT). Five patients had gene therapy. Conclusion: The German PID-NET registry is a precious tool for physicians, researchers, the pharmaceutical industry, politicians, and ultimately the patients, for whom the outcomes will eventually lead to a more timely diagnosis and better treatment.},
  language  = {en}
}