María Belén Almejún1, Bárbara Carolina Campos2, Virginia Patiño3, Miguel Galicchio4, Marta Zelazko5, Matías Oleastro5, Pablo Oppezzo3, Silvia Danielian5. 1. Servicio de Immunología y Reumatología, Hospital Nacional de Pediatría Prof. Dr Juan P. Garrahan, Buenos Aires, Argentina. Electronic address: mbalmejun@gmail.com. 2. Coordinación de Laboratorio, Hospital Nacional de Pediatría Prof. Dr Juan P. Garrahan, Buenos Aires, Argentina. 3. Unidad de Proteínas Recombinantes, Instituto Pasteur, Montevideo, Uruguay. 4. Hospital de Niños Víctor J. Vilela, Rosario, Santa Fé, Argentina. 5. Servicio de Immunología y Reumatología, Hospital Nacional de Pediatría Prof. Dr Juan P. Garrahan, Buenos Aires, Argentina.
Abstract
BACKGROUND: Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by impaired immunoglobulin production and usually presents with a normal quantity of peripheral B cells. Most attempts aiming to classify these patients have mainly been focused on T- or B-cell phenotypes and their ability to produce protective antibodies, but it is still a major challenge to find a suitable classification that includes the clinical and immunologic heterogeneity of these patients. OBJECTIVE: In this study we evaluated the late stages of B-cell differentiation in a heterogeneous population of patients with pediatric-onset CVID to clinically correlate and assess their ability to perform somatic hypermutation (SHM), class-switch recombination (CSR), or both. METHODS: We performed a previously reported assay, the restriction enzyme hotspot mutation assay (IgκREHMA), to evaluate in vivo SHM status. We amplified switch regions from genomic DNA to investigate the quality of the double-strand break repairs in the class-switch recombination process in vivo. We also tested the ability to generate immunoglobulin germline and circle transcripts and to upregulate the activation-induced cytidine deaminase gene through in vitro T-dependent and T-independent stimuli. RESULTS: Our results showed that patients could be classified into 2 groups according to their degree of SHM alteration. This stratification showed a significant association between patients of group A, severe alteration, and the presence of noninfectious complications. Additionally, 60% of patients presented with increased microhomology use at switched regions. In vitro activation revealed that patients with CVID behaved heterogeneously in terms of responsiveness to T-dependent stimuli. CONCLUSIONS: The correlation between noninfectious complications and SHM could be an important tool for physicians to further characterize patients with CVID. This categorization would help to improve elucidation of the complex mechanisms involved in B-cell differentiation pathways.
BACKGROUND: Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by impaired immunoglobulin production and usually presents with a normal quantity of peripheral B cells. Most attempts aiming to classify these patients have mainly been focused on T- or B-cell phenotypes and their ability to produce protective antibodies, but it is still a major challenge to find a suitable classification that includes the clinical and immunologic heterogeneity of these patients. OBJECTIVE: In this study we evaluated the late stages of B-cell differentiation in a heterogeneous population of patients with pediatric-onset CVID to clinically correlate and assess their ability to perform somatic hypermutation (SHM), class-switch recombination (CSR), or both. METHODS: We performed a previously reported assay, the restriction enzyme hotspot mutation assay (IgκREHMA), to evaluate in vivo SHM status. We amplified switch regions from genomic DNA to investigate the quality of the double-strand break repairs in the class-switch recombination process in vivo. We also tested the ability to generate immunoglobulin germline and circle transcripts and to upregulate the activation-induced cytidine deaminase gene through in vitro T-dependent and T-independent stimuli. RESULTS: Our results showed that patients could be classified into 2 groups according to their degree of SHM alteration. This stratification showed a significant association between patients of group A, severe alteration, and the presence of noninfectious complications. Additionally, 60% of patients presented with increased microhomology use at switched regions. In vitro activation revealed that patients with CVID behaved heterogeneously in terms of responsiveness to T-dependent stimuli. CONCLUSIONS: The correlation between noninfectious complications and SHM could be an important tool for physicians to further characterize patients with CVID. This categorization would help to improve elucidation of the complex mechanisms involved in B-cell differentiation pathways.
Authors: Carole Le Coz; Bertram Bengsch; Caroline Khanna; Melissa Trofa; Takuya Ohtani; Brian E Nolan; Sarah E Henrickson; Michele P Lambert; Taylor Olmsted Kim; Jenny M Despotovic; Scott Feldman; Olajumoke O Fadugba; Patricia Takach; Melanie Ruffner; Soma Jyonouchi; Jennifer Heimall; Kathleen E Sullivan; E John Wherry; Neil Romberg Journal: J Allergy Clin Immunol Date: 2019-08-22 Impact factor: 10.793
Authors: Neil Romberg; Carole Le Coz; Salomé Glauzy; Jean-Nicolas Schickel; Melissa Trofa; Brian E Nolan; Michele Paessler; Mina L Xu; Michele P Lambert; Saquib A Lakhani; Mustafa K Khokha; Soma Jyonouchi; Jennifer Heimall; Patricia Takach; Paul J Maglione; Jason Catanzaro; F Ida Hsu; Kathleen E Sullivan; Charlotte Cunningham-Rundles; Eric Meffre Journal: J Allergy Clin Immunol Date: 2018-06-20 Impact factor: 10.793
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