IRF2BP2 is a transcription factor that plays an important role in regulating immune pathways, angiogenesis, apoptosis, and cell differentiation. Defects in this gene have been implicated in immunodeficiency. To deepen the understanding of the clinical implications of IRF2BP2 variants, we sought to clinically characterize and functionally test 34 individuals with IRF2BP2 variants. We collected 34 subjects across 18 families with mutations in IRF2BP2. Records were abstracted for clinical phenotypes. Functional testing was performed on PBMCs. NFAT luciferase gene reporter constructs and quantitative cDNA determinations were used to evaluate repressor activity associated with ectopic expression of various IRF2BP2 mutant constructs in Jurkat cells. Most subjects had immunodeficiency (91%, n = 30 of 33) with variable gastrointestinal (65%, n = 20 of 31) and inflammatory or autoimmune features (57%, n = 17 of 30), including chronic abdominal pain, colitis, diarrhea, constipation, vitiligo, alopecia, and migratory rashes. There was a reduced frequency of memory B cells with poor immunoglobulin production and reduced calcium flux in response to B-cell receptor stimuli. PBMCs had increased apoptosis in vitro compared to healthy controls. Impaired IRF2BP2 repression of NFAT activation was observed using patient-derived mutant IRF2BP2 constructs compared to wild-type constructs. Similarly, TNF-α transcript levels were higher using patient-derived mutations compared to wild-type IRF2BP2 constructs. IRF2BP2 deficiency causes a complex immunodeficiency including gastrointestinal and inflammatory disorders as well as impaired B-cell maturation. Impaired repression of the NFAT pathway appears to enhance proinflammatory signaling through proinflammatory cytokine expression.

Common variable immunodeficiency (CVID) is the largest group of symptomatic primary immune deficiencies; it is characterized by hypogammaglobulinemia, poor response to vaccines and increased susceptibility to infections. Cellular phenotypes and abnormalities have been described both in adaptive and innate immune response. Several classifications of common variable immunodeficiency are based on defects found on T and B cells, which have been correlated with clinical manifestations. In recent years, significant progress has been made in elucidating the genetic mechanisms that result in a IDCV phenotype. Massive sequencing technologies have favored the description of mutations in several genes, but only in 2 % to 10 % of patients. These monogenetic defects are: ICOS, TNFRSF13B (TACI), TNFRS13C (BAFFR), TNRFSF12 (TWEAK), CD19, CD81, CR2 (CD21), MS4A1 (CD20), (CD27), LRBA, CTLA4, PRKCD, PLCG2, NFKB1, NFKB2, PIK3CD, PIK3R, VAV1, RAC1, BLK, IKZF1 (IKAROS) and IRF2BP2. These findings have provided a possible explanation for the pathogenesis of IDCV, since these molecules play an important role in the co-operation between B and T cells in the germinal center, as well as in intrinsic signaling pathways of both. La inmunodeficiencia común variable constituye el mayor grupo de inmunodeficiencias primarias sintomáticas; se caracterizan por hipogammaglobulinemia, pobre respuesta a las vacunas y susceptibilidad aumentada a las infecciones. Se han descrito fenotipos celulares y anormalidades tanto en la respuesta inmune adaptativa como en la innata. Varias de las clasificaciones se basan en los defectos encontrados en las células T y B, que se han correlacionado con las manifestaciones clínicas. En los últimos años se ha progresado significativamente en el desentrañamiento de los mecanismos genéticos que resultan en un fenotipo de inmunodeficiencia común variable. Las tecnologías de secuenciación masiva han favorecido la descripción de mutaciones en varios genes, pero solo en 2 a 10 % de los pacientes. Estos defectos monogénicos son ICOS, TNFRSF13B (TACI), TNFRS13C (BAFFR), TNRFSF12 (TWEAK), CD19, CD81, CR2 (CD21), MS4A1 (CD20), TNFRSF7 (CD27), LRBA, CTLA4, PRKCD, PLCG2, NFKB1, NFKB2, PIK3CD, PIK3R, VAV1, RAC1, BLK, IKZF1 (IKAROS) y IRF2BP2. Los anteriores hallazgos han proporcionado una posible explicación para la patogénesis de la inmunodeficiencia común variable, ya que esas moléculas desempeñan un papel importante en la cooperación entre las células B y T en el centro germinal, así como en las vías de señalización intrínseca de ambas.

Common variable immunodeficiency (CVID) is a primary antibody deficiency characterised by hypogammaglobulinaemia, impaired production of specific antibodies after immunisation and increased susceptibility to infections. CVID shows a considerable phenotypical and genetic heterogeneity. In contrast to many other primary immunodeficiencies, monogenic forms count for only 2-10% of patients with CVID. Genes that have been implicated in monogenic CVID include ICOS, TNFRSF13B (TACI), TNFRSF13C (BAFF-R), TNFSF12 (TWEAK), CD19, CD81, CR2 (CD21), MS4A1 (CD20), TNFRSF7 (CD27), IL21, IL21R, LRBA, CTLA4, PRKCD, PLCG2, NFKB1, NFKB2, PIK3CD, PIK3R1, VAV1, RAC2, BLK, IKZF1 (IKAROS) and IRF2BP2 With the increasing number of disease genes identified in CVID, it has become clear that CVID is an umbrella diagnosis and that many of these genetic defects cause distinct disease entities. Moreover, there is accumulating evidence that at least a subgroup of patients with CVID has a complex rather than a monogenic inheritance. This review aims to discuss current knowledge regarding the molecular genetic basis of CVID with an emphasis on the relationship with the clinical and immunological phenotype.

Genome-wide association studies have shown a pattern of rare copy number variations and single nucleotide polymorphisms in patients with common variable immunodeficiency disorder (CVID), which was recognizable by a support vector machine (SVM) algorithm. However, rare monogenic causes of CVID might lack such a genetic fingerprint. We sought to identify a unique monogenic cause of familial immunodeficiency and evaluate the use of SVM to identify patients with possible monogenic disorders. A family with multiple members with a diagnosis of CVID was screened by using whole-exome sequencing. The proband and other subjects with mutations associated with CVID-like phenotypes were screened through the SVM algorithm from our recent CVID genome-wide association study. RT-PCR, protein immunoblots, and in vitro plasmablast differentiation assays were performed on patient and control EBV lymphoblastoids cell lines. Exome sequencing identified a novel heterozygous mutation in IRF2BP2 (c.1652G>A:p.[S551N]) in affected family members. Transduction of the mutant gene into control human B cells decreased production of plasmablasts in vitro, and IRF2BP2 transcripts and protein expression were increased in proband versus control EBV-immortalized lymphoblastoid cell lines. The SVM algorithm categorized the proband and subjects with other immunodeficiency-associated gene variants in TACI, BAFFR, ICOS, CD21, LRBA, and CD27 as genetically dissimilar from polygenic CVID. A novel IRFBP2 mutation was identified in a family with autosomal dominant CVID. Transduction experiments suggest that the mutant protein has an effect on B-cell differentiation and is likely a monogenic cause of the family's CVID phenotype. Successful grouping by the SVM algorithm suggests that our family and other subjects with rare immunodeficiency disorders cluster separately and lack the genetic pattern present in polygenic CVID cases.