Combined Immunodeficiency Phenotype Research Articles

Neurodevelopmental disorder and immunodeficiency

Background: Neurodevelopment is closely entwined with immune maturation and function during embryogenesis. While haematopoietic-derived microglia have recognized roles in a number of neurodevelopmental processes, the contribution of molecules classically involved in the immune system (including complement, toll-like receptors, and cytokines) are also emerging. To date, approximately 11% of genes known to cause primary immunodeficiency also confer varying degrees of neurological abnormalities. These can range from intellectual disability, cognitive and behavioural disorders, through to seizures, spasticity, and motor development delay. However, very rarely are sensory processing defects associated with aberrations of the immune system. Aims: To define the clinical presentation and immune phenotype of a novel syndrome encompassing immunodeficiency, neurodevelopmental abnormalities, and altered pain sensitivity in two siblings. Methods: Comprehensive retrospective review of the patient’s charts were performed, in accordance with local research ethics board approval. Results: We describe two teenage sisters who presented with recurrent sinopulmonary infections, lymphopenia affecting both B and T cells, developmental delay, learning and processing disorder, seizures, and reduced sensitivity to pain. Other features include bronchogenic cyst, microscopic hematuria, oral ulcers, papular urticaria, and keratosis pilaris. Conclusion: An underlying defect in genes known to cause primary immunodeficiency was not identified, suggesting the role of an as-yet undefined molecule at the crossroads of immunity, neurodevelopment, and sensory processing. Statement of novelty: We report on two patients, siblings, with a novel phenotype of combined immunodeficiency, neurodevelopmental delay, and reduced sensitivity to painful stimuli.

Novel RAG2 Mutation in a Patient with Leaky Severe Combined Immunodeficiency

T and B lymphocytes development and function are highly dependent on Recombination Activating Genes (RAG) 1 and 2. RAG mutations result in different degree of T and B cell impaired function, broad clinical manifestations, and immunological manifestations. Pathogenic mutations cause severe combined immunodeficiency (SCID) phenotype, while hypomorphic mutations are responsible for leaky or partial SCID.
 Here, we described a 4-year-old girl who had a persistent diarrhea, recurrent infection and vomiting. Although physicians were suspicious about autoimmune enteropathy, her molecular report showed a homozygous and novel RAG2 mutation in its core domain. The number of CD4 T cells and IgA level were lower than normal ranges. Lack of IgA brought about different GI complications. Our patient died finally because of the liver and gallbladder failure.

A newborn with multiple intestinal atresias found to have variants in tetratricopeptide repeat domain 7A gene

We report a male infant born with multiple intestinal atresias (MIA) prompting early genetic testing. Bi-allelic, compound heterozygous variants in tetratricopeptide repeat domain 7A (TTC7A) gene were identified. TTC7A is involved in transporting phosphatidylinositol 4-kinase IIIα into the plasma membrane (1). Mutations in this gene disrupt intestinal development and polarity, causing intestinal diseases such as atresia, enteropathy, and very early onset inflammatory bowel disease (VEO-IBD), as well as variable degrees of immunodeficiency (1).The identification of variants in TTC7A gene prompted an immune evaluation since as many as 75% of patients with TTC7A mutations reported in the literature have an underlying immunodeficiency (2). Flow cytometry was relatively unremarkable except for a slightly low memory T-cell count and percentage. NK-cell and B-cell numbers and percentages were appropriate for age. His phytohemagglutinin response was relatively low, but still significant, suggesting a possible component of combined immunodeficiency. To further characterize his T-cell function, we assessed his T-cell proliferation response to anti-CD3, which showed moderately decreased response of CD45+ lymphocytes and CD3+ T-cells to soluble anti-CD3 alone. However, co-stimulation with anti-CD3+anti-CD28 and anti-CD3+IL-2 normalized his T-cell proliferative response. Immunoglobulins were all low. Given his subtle T-cell defect and hypogammaglobulinemia, he was classified as having MIA with combined immunodeficiency (MIA-CID) phenotype of TTC7A.Cobalamin was tried in this patient as it has a low side effect profile and showed benefits in gut motility and intestinal tract luminal narrowing in a TTC7A zebrafish model (3). We considered investigational use of leflunomide, which showed the most promising results in the same zebrafish model (3). Bowel and hematopoietic stem-cell transplantation were considered too. Enterectomy was also offered, as this was shown to be effective in a case report of two patients with similar MIA-CID TTC7A phenotype (4). Unfortunately, the patient did not respond to steroids or cobalamin. His clinical condition worsened, and he passed away at four months of age.Mutations in the TTC7A gene result in various gastrointestinal pathologies with varying degrees of immunodeficiency in approximately 75% of patients (2). All patients with MIA or VEO-IBD should have an immune evaluation and genetic testing.

Lymphoma as an Exclusion Criteria for CVID Diagnosis Revisited.

Hypogammaglobulinemia in a context of lymphoma is usually considered as secondary and prior lymphoma remains an exclusion criterion for a common variable immunodeficiency (CVID) diagnosis. We hypothesized that lymphoma could be the revealing symptom of an underlying primary immunodeficiency (PID), challenging the distinction between primary and secondary hypogammaglobulinemia. Within a French cohort of adult patients with hypogammaglobulinemia, patients who developed a lymphoma either during follow-up or before the diagnosis of hypogammaglobulinemia were identified. These two chronology groups were then compared. For patients without previous genetic diagnosis, a targeted next-generation sequencing of 300 PID-associated genes was performed. A total of forty-seven patients had developed 54 distinct lymphomas: non-Hodgkin B cell lymphoma (67%), Hodgkin lymphoma (26%), and T cell lymphoma (7%). In 25 patients, lymphoma developed prior to the diagnosis of hypogammaglobulinemia. In this group of patients, Hodgkin lymphoma was overrepresented compared to the group of patients in whom lymphoma occurred during follow-up (48% versus 9%), whereas MALT lymphoma was absent (0 versus 32%). Despite the histopathological differences, both groups presented with similar characteristics in terms of age at hypogammaglobulinemia diagnosis, consanguinity rate, or severe T cell defect. Overall, genetic analyses identified a molecular diagnosis in 10/47 patients (21%), distributed in both groups and without peculiar gene recurrence. Most of these patients presented with a late onset combined immunodeficiency (LOCID) phenotype. Prior or concomitant lymphoma should not be used as an exclusion criteria for CVID diagnosis, and these patients should be investigated accordingly.

Role of foxn1 in Xenopus laevis thymopoiesis.

Abstract The transcription factor forkhead box N1 (FOXN1) plays a pivotal role in differentiation of thymic epithelial cells (TECs) essential for intrathymic T cell education and keratinocyte development. Mutations in murine foxn1 are associated with T− B+ NK+ nude/severe combined immunodeficiency (SCID) phenotype. In humans FOXN1 mutations also lead to thymic aplasia or hypoplasia, hair loss and dysmorphic nails. In the amphibian Xenopus tropicalis, foxn1−/− line exhibited loss of thymi formation and absence of mature T-cells, similar with Foxn1−/− murine line. Due to expanded resources in immunobiology of X. laevis (a close relative of X. tropicalis), we generated a novel foxn1-deficient X. laevis model by using the CRISPR/Cas9. foxn1 crispants shows a high mutational efficiency (30–90%) and about 25% of tadpoles (stage 55–56), exhibit hypoplastic thymi. foxn1 disruption resulted in significant reduction of T-cell markers transcript levels, detected by RT-PCR. Furthermore, spleen of foxn1 crispants had markedly reduced CD3e staining compared to controls. Interestingly, Mycobacterium marinum (M. marinum) infection of tadpoles results in noninflammatory CD8 negative- and iT cell–mediated response, while foxn1 mutations in X. laevis appeared to affect tolerigenic innate immune response of infected tadpoles. This foxn1-deficient transgenic line will empower X. laevis as nonmammalian alternative experimental organism for studying host interaction with to non-tuberculosis mycobacteria. Currently, we are investigating mechanisms by which foxn1 mutation alter innate immunity of M. marinum inoculated tadpoles and evaluating tolerance/resistance by analysing the inflammatory/anti-inflammatory cytokine profile.

Case Report: Hypomorphic Function and Somatic Reversion in DOCK8 Deficiency in One Patient With Two Novel Variants and Sclerosing Cholangitis

DOCK8 deficiency is a combined immunodeficiency due to biallelic variants in dedicator of cytokinesis 8 (DOCK8) gene. The disease has a wide clinical spectrum encompassing recurrent infections (candidiasis, viral and bacterial infections), virally driven malignancies and immune dysregulatory features, including autoimmune (cytopenia and vasculitis) as well as allergic disorders (eczema, asthma, and food allergy). Hypomorphic function and somatic reversion of DOCK8 has been reported to result in incomplete phenotype without IgE overproduction. Here we describe a case of DOCK8 deficiency in a 8-year-old Caucasian girl. The patient’s disease was initially classified as autoimmune thrombocytopenia, which then evolved toward a combined immunodeficiency phenotype with recurrent infections, persistent EBV infection and lymphoproliferation. Two novel variants (one deletion and one premature stop codon) were characterized, resulting in markedly reduced, but not absent, DOCK8 expression. Somatic reversion of the DOCK8 deletion was identified in T cells. Hypomorphic function and somatic reversion were associated with restricted T cell repertoire, decreased STAT5 phosphorylation and impaired immune synapse functioning in T cells. Although the patient presented with incomplete phenotype (absence of markedly increase IgE and eosinophil count), sclerosing cholangitis was incidentally detected, thus indicating that hypomorphic function and somatic reversion of DOCK8 may delay disease progression but do not necessarily prevent from severe complications.

A novel splice site variant in FOXN1 in a patient with abnormal newborn screening for severe combined immunodeficiency and congenital lymphopenia

Background: The Forkhead box protein N1 (FOXN1) is a key regulator of thymic epithelial development, and its complete deficiency leads to a nude-severe combined immunodeficiency (SCID) phenotype. More recently, heterozygous mutations in FOXN1 have been linked with a syndrome of congenital lymphopenia and a wide clinical spectrum, with most cases being caused by missense mutations. Aim: To broaden the genotypic and phenotypic spectrum of heterozygous FOXN1 deficiency. Methods: Case report of a patient with FOXN1 haploinsufficiency due to a novel splice-site mutation. Results: Our patient was identified at 3 weeks of life given an abnormal newborn screen (NBS) for SCID, and was found to have congenital lymphopenia preferentially affecting CD8+ T-cells. Her cellular and humoral function were both excellent, and she has remained entirely asymptomatic and thriving for the first 3 years of her life. The patient was found on whole exome sequencing to carry a heterozygous splice-site mutation in the FOXN1 gene, affecting the Forkhead domain. The mutation was also identified in her asymptomatic mother. Conclusion: Heterozygous FOXN1 mutations are an increasingly-recognized cause of congenital lymphopenia. Our experience suggests most patients remain clinically well, with main manifestation including T-lymphopenia, mostly affecting CD8+ cells. Identification of the same variant in an asymptomatic parent suggests age-dependent improvement in T-cell counts and an overall benign course, while provides impetus for diligent conservative management with regular follow-up. Statement of novelty: Heterozygous FOXN1 deficiency is a relatively new entity, attributed in most cases to missense mutations in FOXN1. To further expand the knowledge basis regarding this emerging disorder, as well as its genotypic repertoire, we herein report a case of heterozygous FOXN1 deficiency caused by a splice site mutation.

Homozygous NF-kB1 mutation causing combined immunodeficiency: a histopathological analysis

Introduction: The nuclear factor-kB (NF-kB) signaling pathway plays a major role in mediating multiple cellular processes, including immune and inflammatory responses. Aims: We describe the histopathological findings of lymph nodes from a patient with a homozygous NF-kB subunit 1 (NF-kB1) mutation causing a combined immunodeficiency phenotype. Results: A nodal biopsy was performed for lymphadenopathy evaluation, in the context of development of persistent EBV infection. Our findings show that this patient has normal lymph node tissue present, however, abnormal histopathology features were observed, including atrophic germinal centers. B cell subset components within the B cell domain were also analyzed. The development of the B cell response during EBV infection was found to be significantly impaired. Conclusion: Aberrant signaling due to NF-kB1 deficiency has a significant impact on the development of B cell immunoproliferative responses. Statement of novelty: We report on the abnormal histopathology findings of lymph node biopsy from a patient with homozygous NF-kB1 mutation.

A clinical case of the X-linked moesin deficiency

With the increasing availability of genetic testing, the population of patients diagnosed with CVID breaks down into groups depending on monogenic defects. There is more and more evidence that adults can have combined immunodeficiencies with a late onset.
 This article discusses a clinical case of X-linked moesin-associated immunodeficiency (X-MAID). This is a recently described immunodeficiency, which mostly manifests itself at an early age with severe lymphopenia and hypogammaglobulinemia, fluctuating monocytopenia and neutropenia, a weak immune response to vaccine antigens, and increased susceptibility to bacteria and type 3 human herpesvirus.
 X-MAID, X-linked immunodeficiency with a recessive mode of inheritance, is caused by genetic defects in the MOESIN gene (membrane organizing spike elongation protein, MSN). Until recently, there were records of 10 people with this mutation, 9 of which have the phenotype of severe combined immunodeficiency (SCID). The patient described in this article has been under observation since the age of 12 and diagnosed with SCID due to an IgG decrease accompanied by infectious-purulent processes of the respiratory tract and diarrheal syndrome.
 However, the patient did not entirely fit into the typical clinical picture of CVID due to a severe therapy-torpid papillomavirus infection, the increased number of switched memory B-cells, IgG isolated decrease, persistent severe leukopenia and lymphopenia of CD4+ cells. In accordance with the clinical picture and the results of the immunological examination, combined immunodeficiency was surmised. After a full exome DNA sequencing chrX: g.64951012C T missense type mutation was found in exon 5 of the MSN gene (change in the ENSP00000353408.5:p.Arg171Trp protein). X-MAID was therefore confirmed.
 Of the 9 described patients with a similar mutation, 8 had a clinical picture of severe combined immune deficiency. This clinical case confirms the possibility of a milder clinical phenotype development with a late onset under the guise of CVID and shows the need for molecular genetic examination of the adult population of patients with impaired antibody synthesis. The verification of the diagnosis allows not only to determine the prognosis and tactics of the therapy, but also to carry out genetic family counseling and to offer a possibility of giving birth to healthy offspring.

A Decade Experience on Severe Combined Immunodeficiency Phenotype in Oman, Bridging to Newborn Screening.

IntroductionSevere combined immunodeficiency (SCID) results from various monogenic defects that impair immune function and brings on early severe and life-threatening infections. The main stay of treatment for SCID is hematopoietic stem cell transplant (HSCT) with near normal survival at 5 years for an early transplant done at or before the age of 3.5 months of life and the patient is maintained free of infections. Although overall rare, it constitutes a major burden on affected children, their families and on the health system especially in communities with a high rate of consanguinity where incidence and prevalence of recessive inborn errors of immunity (IEI) are expected to be high.MethodHere, we report the clinical, immunological, and molecular findings in 36 children diagnosed with SCID from a single tertiary center in Oman for the last decade.ResultsWe observed a median annual incidence rate of 4.5 per 100,000 Omani live births, and 91.7% of affected children were born to consanguineous parents. Twenty-three children (63.9%) fulfilled the criteria for typical SCID. The median age at onset, diagnosis and diagnostic delay were 54, 135, and 68 days, respectively. The most common clinical manifestations were pneumonia, septicemia, and chronic diarrhea. Eleven children (30.6%) have received hematopoietic stem cell transplant (HSCT) with a survival rate of 73%. The most frequent genetic cause of SCID in this cohort (n = 36) was (RAG-1), encoding for recombination activating gene (n = 5, 13.9%). Similarly, Major histocompatibility complex type II deficiency accounted for (n = 5, 13.9%) of our cohort.ConclusionOur report broadens the knowledge of clinical and molecular manifestations in children with SCID in the region and highlights the need to initiate newborn based screening program (NBS) program.

DNA-PKcs chemical inhibition versus genetic mutation: Impact on the junctional repair steps of V(D)J recombination

Spontaneous DNA-PKcs deficiencies in animals result in a severe combined immunodeficiency (SCID) phenotype because DNA-PKcs is required to activate Artemis for V(D)J recombination coding end hairpin opening. The impact on signal joint formation in these spontaneous mutant mammals is variable. Genetically engineered DNA-PKcs null mice and cells from them show a >1,000-fold reduction in coding joint formation and minimal reduction in signal joint formation during V(D)J recombination. Does chemical inhibition of DNA-PKcs mimic this phenotype? M3814 (also known as Nedisertib) is a potent DNA-PKcs inhibitor. We find here that M3814 causes a quantitative reduction in coding joint formation relative to signal joint formation. The sequences of signal and coding junctions were within normal limits, though rare coding joints showed novel features. The signal junctions generally did not show evidence of resection into the signal ends that is often seen in cells that have genetic defects in DNA-PKcs. Comparison of the chemical inhibition findings here with the known results for spontaneous and engineered DNA-PKcs mutant mammals is informative for considering pharmacologic small molecule inhibition of DNA-PKcs in various types of neoplasia.

Heterozygous FOXN1 Variants Cause Low TRECs and Severe T Cell Lymphopenia, Revealing a Crucial Role of FOXN1 in Supporting Early Thymopoiesis

FOXN1 is the master regulatory gene of thymic epithelium development. FOXN1 deficiency leads to thymic aplasia, alopecia, and nail dystrophy, accounting for the nude/severe combined immunodeficiency (nu/SCID) phenotype in humans and mice. We identified several newborns with low levels of Tcell receptor excision circles (TRECs) and Tcell lymphopenia at birth, who carried heterozygous loss-of-function FOXN1 variants. Longitudinal analysis showed persistent Tcell lymphopenia during infancy, often associated with nail dystrophy. Adult individuals with heterozygous FOXN1 variants had in most cases normal CD4+ but lower than normal CD8+ cellcounts. We hypothesized a FOXN1 gene dosage effect on the function of thymic epithelial cells (TECs) and thymopoiesis and postulated that these effects would be more prominent early in life. To test this hypothesis, we analyzed TEC subset frequency and phenotype, early thymic progenitor (ETP) cell count, and expression of FOXN1 target genes (Ccl25, Cxcl12, Dll4, Scf, Psmb11, Prss16, and Cd83) in Foxn1nu/+ (nu/+) mice and age-matched wild-type (+/+) littermate controls. Both the frequency and the absolute count of ETP were significantly reduced in nu/+ mice up to 3weeks of age. Analysis of the TEC compartment showed reduced expression of FOXN1 target genes and delayed maturation of the medullary TEC compartment in nu/+ mice. These observations establish a FOXN1 gene dosage effect on thymic function and identify FOXN1 haploinsufficiency as an important genetic determinant of Tcell lymphopenia at birth.

Noncoding RNA transcription at enhancers and genome folding in cancer.

Changes of nuclear localization of lineage‐specific genes from a transcriptionally inert to permissive environment are a crucial step in establishing the identity of a cell. Noncoding RNA transcription‐mediated genome folding and activation of target gene expression have been found in a variety of cell types. Noncoding RNA ThymoD (thymocyte differentiation factor) transcription at superenhancers is essential for mouse T‐cell lineage commitment. The cessation of ThymoD transcription abolishes transcription‐mediated demethylation, recruiting looping factors such as the cohesin complex, CCCTC‐binding factor (CTCF), ultimately leading to the phenotype of severe combined immunodeficiency and T‐cell leukemia/lymphoma. In this review, we describe the functional role of RNA polymerase II‐mediated transcription at enhancers and in genome folding. We also highlight the involvement of faulty activation or suppression of enhancer transcription and enhancer‐promoter interaction in cancer development.

Clinical and Immunological Characterization of ICF Syndrome in Japan

Immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a rare autosomal recessive primary immunodeficiency. Hypogammaglobulinemia is a major manifestation of ICF syndrome, but immunoglobulin replacement therapy does not seem to be effective for some ICF patients. Therefore, we aimed to reassess the immunological characteristics of this syndrome. Eleven Japanese patients with ICF syndrome were enrolled. We performed whole-exome sequencing in four cases and homozygosity mapping using SNP analysis in two. We evaluated their clinical manifestations and immunological status. We newly diagnosed six ICF patients who had tentatively been diagnosed with common variable immunodeficiency. We identified two novel mutations in the DNMT3B gene and one novel mutation in the ZBTB24 gene. All patients showed low serum IgG and/or IgG2 levels and were treated by periodic immunoglobulin replacement therapy. Three of the six patients showed worse results of the mitogen-induced lymphocyte proliferation test. Analyses of lymphocyte subpopulations revealed that CD19+CD27+ memory B cells were low in seven of nine patients, CD3+ T cells were low in three patients, CD4/8 ratio was inverted in five patients, CD31+ recent thymic emigrant cells were low in two patients, and CD19+ B cells were low in four patients compared with those in the normal controls. ICF2 patients showed lower proportions of CD19+ B cells and CD16+56+ NK cells and significantly higher proportions of CD3+ T cells than ICF1 patients. T cell receptor excision circles were undetectable in two patients. Despite being treated by immunoglobulin replacement therapy, three patients died of influenza virus, fatal viral infection with persistent Epstein-Barr virus infection, or JC virus infection. One of three dead patients showed normal intelligence with mild facial anomaly. Two patients presented with autoimmune or inflammatory manifestations. Infectious episodes decreased in three patients who were started on trimethoprim-sulfamethoxazole and/or antifungal drugs in addition to immunoglobulin replacement therapy. These patients might have suffered from T cell immunodeficiency. These results indicate that patients with ICF syndrome have a phenotype of combined immunodeficiency. Thus, to achieve a better prognosis, these patients should be treated as having combined immunodeficiency in addition to receiving immunoglobulin replacement therapy.

MHC-II Deficiency Among Egyptians: Novel Mutations and Unique Phenotypes

MHC class II deficiency leads to defective CD4+ T-cell function that results from impaired antigen presentation. A genetic disorder in 1 of 4 genes results in this syndrome that is associated with the clinical phenotype of combined immunodeficiency. To describe the clinical, immunological, and molecular characteristics of 10 Egyptian patients from 9 different families having presented with MHC class II deficiency between 2012 and2017. An initial diagnosis based on the combination of clinical features and low HLA-DR expression by flow cytometry was confirmed by genetic analyses. Symptoms included failure to thrive (n= 9), persistent diarrhea (n= 5), and pneumonia (n= 8). Septicemia due to coagulase-negative staphylococci (n= 1) and Candida krusei (n= 1) was diagnosed. Nine patients orally received the live attenuated polio vaccine, of whom 3 developed acute flaccid paralysis thereafter. Nine patients received the BCG vaccine and none developed obvious signs of BCGitis. Four patients carried RFXANK gene mutations, 3 carried RFX5 gene mutations, 1 carried a CIITA gene mutation, and none carried RFXAP gene mutations. Six of the 7 detected mutations were previously unreported mutations: c.431T>C, c.247_250delTCAG, and c.600delG in the RFXANK gene; c.116+1G>A and c.715C>T in the RFX5 gene; and c.929delA in the CIITA gene. Given that Egypt is a North African country with a high rate of consanguinity, MHC class II deficiency is not rare. However, the molecular defects differ from those reported in nearby countries. Early diagnosis must be based on suspicious clinical signs and laboratory diagnosis because the defect can be missed by T-cell receptor excision circles based on neonatal screening.

Prevalence and clinical challenges among adults with primary immunodeficiency and recombination-activating gene deficiency

Prevalence and clinical challenges among adults with primary immunodeficiency and recombination-activating gene deficiency

Clinical characteristics of human recombination activating gene 1 mutations in 8 immunodeficiency patients with diverse phenotypes

Objective: To investigate the clinical characteristics of 8 immunodeficiency cases caused by human recombination activating gene 1 (RAG1) mutations, and to explore the relationship among genotypes, clinical manifestations and immunophenotypes. Methods: Clinical data were collected and analyzed from patients with RAG1 mutations who visited the Department of Clinical Immunology, Children's Hospital of Fudan University between October 2013 and June 2017. The data included clinical manifestations, immunophenotypes and genotypes. Results: A total of 8 patients were diagnosed with RAG1 deficiency (6 boys and 2 girls). The minimum age of onset was 2 months, and the maximum age was 4 months. The minimum age of diagnosis was 2 months, and the maximum age was 13 years. Four patients had a family history of infant death due to severe infections. Two cases were born to the same consanguineous parents. All cases had recurrent infections, including involvement of respiratory tract (8 cases), digestive tract (6 cases), urinary tract (1 case), and central nervous system (1 case). The pathogens of infection included bacteria, viruses and fungi. Rotavirus was found in 3 cases, cytomegalovirus (CMV) in 5 cases, bacillus Calmette-Guérin adverse reaction in 2 cases (1 of whom had a positive acid-fast smear from lymph node puncture fluid), fungal infection in 3 cases. One case had multiple nodular space-occupying lesions in lungs and abdominal cavity complicated with multiple bone destruction. The peripheral blood lymphocyte counts of all patients ranged between 0.1 ×10(9)/L and 3.3×10(9)/L (median, 0.65×10(9)/L). Eosinophilia was found in 3 cases (range, (0.48-1.69) ×10(9)/L). The patients were classified according to immunophenotype as severe combined immunodeficiency phenotype (4 cases), leaky severe combined immunodeficiency (2 cases), Omenn syndrome (1 case) and combined immunodeficiency (1 case) . Decreased serum IgG levels were found in 3 cases, increased serum IgM levels in 3 cases, increased serum IgE levels in 5 cases. RAG1 homozygous mutations were detected in 5 cases and RAG1 compound heterozygous mutations in 3 cases. Two novel mutations and six previously reported mutations were identified. Three cases were successfully treated with hematopoietic stem cell transplantation. Four cases died due to infections, and the 13 year-old patient was still under follow-up in the outpatient clinic. Conclusions: Different RAG1 gene mutations can lead to diverse clinical presentations and immune phenotypes. Clinicians should pay attention to the family history of infant death with severe infection. In that situation, immunological evaluation and gene detection should be performed as early as possible.

Novel nonsense gain-of-function NFKB2 mutations associated with a combined immunodeficiency phenotype

AbstractNF-κB signaling through its NFKB1-dependent canonical and NFKB2-dependent noncanonical pathways plays distinctive roles in a diverse range of immune processes. Recently, mutations in these 2 genes have been associated with common variable immunodeficiency (CVID). While studying patients with genetically uncharacterized primary immunodeficiencies, we detected 2 novel nonsense gain-of-function (GOF) NFKB2 mutations (E418X and R635X) in 3 patients from 2 families, and a novel missense change (S866R) in another patient. Their immunophenotype was assessed by flow cytometry and protein expression; activation of canonical and noncanonical pathways was examined in peripheral blood mononuclear cells and transfected HEK293T cells through immunoblotting, immunohistochemistry, luciferase activity, real-time polymerase chain reaction, and multiplex assays. The S866R change disrupted a C-terminal NF-κΒ2 critical site affecting protein phosphorylation and nuclear translocation, resulting in CVID with adrenocorticotropic hormone deficiency, growth hormone deficiency, and mild ectodermal dysplasia as previously described. In contrast, the nonsense mutations E418X and R635X observed in 3 patients led to constitutive nuclear localization and activation of both canonical and noncanonical NF-κΒ pathways, resulting in a combined immunodeficiency (CID) without endocrine or ectodermal manifestations. These changes were also found in 2 asymptomatic relatives. Thus, these novel NFKB2 GOF mutations produce a nonfully penetrant CID phenotype through a different pathophysiologic mechanism than previously described for mutations in NFKB2.

FOXN1 Deficiency: from the Discovery to Novel Therapeutic Approaches.

Since the discovery of FOXN1 deficiency, the human counterpart of the nude mouse, a growing body of evidence investigating the role of FOXN1 in thymus and skin, has been published. FOXN1 has emerged as fundamental for thymus development, function, and homeostasis, representing the master regulator of thymic epithelial and T cell development. In the skin, it also plays a pivotal role in keratinocytes and hair follicle cell differentiation, although the underlying molecular mechanisms still remain to be fully elucidated. The nude severe combined immunodeficiency phenotype is indeed characterized by the clinical hallmarks of athymia with severe T cell immunodeficiency, congenital alopecia, and nail dystrophy. In this review, we summarize recent discoveries in the field and give interesting perspective about new and promising therapeutic approaches for disorders of immune system with athymia.

Mutations in linker for activation of T cells (LAT) lead to a novel form of severe combined immunodeficiency

Signaling through the T-cell receptor (TCR) is critical for T-cell development and function. Linker for activation of Tcells (LAT) is a transmembrane adaptor signaling molecule that is part of the TCR complex and essential for T-cell development, as demonstrated by LAT-deficient mice, which show a complete lack of peripheral Tcells. We describe a pedigree affected by a severe combined immunodeficiency phenotype with absent Tcells and normal B-cell and natural killer cell numbers. Anovel homozygous frameshift mutation in the gene encoding for LAT was identified in this kindred. Genetic, molecular, and functional analyses were used to identify and characterize the LAT defect. Clinical and immunologic analysis of patients was also performed and reported. Homozygosity mapping was used to identify potential defective genes. Sanger sequencing of the LAT gene showed a mutation that resulted in a premature stop codon and protein truncation leading to complete loss of function and loss of expression of LAT in the affected family members. We also demonstrate loss of LAT expression and lack of TCR signaling restoration in LAT-deficient cell lines reconstituted with a synthetic LAT gene bearing this severe combined immunodeficiency mutation. For the first time, the results of this study show that inherited LAT deficiency should be considered in patients withcombined immunodeficiency with T-cell abnormalities.