Genetic Evaluation of the Patients with Clinically Diagnosed Inborn Errors of Immunity by Whole Exome Sequencing: Results from a Specialized Research Center for Immunodeficiency in Türkiye.

Molecular diagnosis of inborn errors of immunity (IEI) plays a critical role in determining patients' long-term prognosis, treatment options, and genetic counseling. Over the past decade, the broader utilization of next-generation sequencing (NGS) techniques in both research and clinical settings has facilitated the evaluation of a significant proportion of patients for gene variants associated with IEI. In addition to its role in diagnosing known gene defects, the application of high-throughput techniques such as targeted, exome, and genome sequencing has led to the identification of novel disease-causing genes. However, the results obtained from these different methods can vary depending on disease phenotypes or patient characteristics. In this study, we conducted whole-exome sequencing (WES) in a sizable cohort of IEI patients, consisting of 303 individuals from 21 different clinical immunology centers in Türkiye. Our analysis resulted in likely genetic diagnoses for 41.1% of the patients (122 out of 297), revealing 52 novel variants and uncovering potential new IEI genes in six patients. The significance of understanding outcomes across various IEI cohorts cannot be overstated, and we believe that our findings will make a valuable contribution to the existing literature and foster collaborative research between clinicians and basic science researchers.

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation.

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27(+) memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src-kinase Syk-transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

Therapeutic modalities and clinical outcomes in a large cohort with LRBA deficiency and CTLA4 insufficiency.

BACKGROUND: LPS-responsive beige-like anchor (LRBA) deficiency (LRBA-/-) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) insufficiency (CTLA4+/-) are mechanistically overlapped diseases presenting with recurrent infections and autoimmunity. The effectiveness of different treatment regimens remains unknown. OBJECTIVE: Our aim was to determine the comparative efficacy and long-term outcome of therapy with immunosuppressants, CTLA4-immunoglobulin (abatacept), and hematopoietic stem cell transplantation (HSCT) in a single-country multicenter cohort of 98 patients with a 5-year median follow-up. METHODS: The 98 patients (63 LRBA-/- and 35 CTLA4+/-) were followed and evaluated at baseline and every 6 months for clinical manifestations and response to the respective therapies. RESULTS: The LRBA-/- patients exhibited a more severe disease course than did the CTLA4+/- patients, requiring more immunosuppressants, abatacept, and HSCT to control their symptoms. Among the 58 patients who received abatacept as either a primary or rescue therapy, sustained complete control was achieved in 46 (79.3%) without severe side effects. In contrast, most patients who received immunosuppressants as primary therapy (n = 61) showed either partial or no disease control (72.1%), necessitating additional immunosuppressants, abatacept, or transplantation. Patients with partial or no response to abatacept (n = 12) had longer disease activity before abatacept therapy, with higher organ involvement and poorer disease outcomes than those with a complete response. HSCT was performed in 14 LRBA-/- patients; 9 patients (64.2%) showed complete remission, and 3 (21.3%) continued to receive immunosuppressants after transplantation. HSCT and abatacept therapy gave rise to similar probabilities of survival. CONCLUSIONS: Abatacept is superior to immunosuppressants in controlling disease manifestations over the long term, especially when started early, and it may provide a safe and effective therapeutic alternative to transplantation.

Defective Treg generation and increased type 3 immune response in leukocyte adhesion deficiency 1.

In 15 Turkish LAD-1 patients and controls, we assessed the impact of pathogenic ITGB2 mutations on Th17/Treg differentiation and functions, and innate lymphoid cell (ILC) subsets. The percentage of peripheral blood Treg cells, in vitro-generated induced Tregs differentiated from naive CD4+ T cells were decreased despite the elevated absolute counts of CD4+ cells in LAD-1 patients. Serum IL-23 levels were elevated in LAD-1 patients. Post-curdlan stimulation, LAD-1 patient-derived PBMCs produced more IL-17A. Additionally, the percentages of CD18-deficient Th17 cells expanded from total or naïve CD4+ T cells were higher. The blood ILC3 subset was significantly elevated in LAD-1. Finally, LAD-1 PBMCs showed defects in trans-well migration and proliferation and were more resistant to apoptosis. Defects in de novo generation of Tregs from CD18-deficient naïve T cells and elevated Th17s, and ILC3s in LAD-1 patients' peripheral blood suggest a type 3-skewed immunity and may contribute to LAD-1-associated autoimmune symptoms.

Atypical Localization of Eczema Discriminates DOCK8 or STAT3 Deficiencies from Atopic Dermatitis.

PURPOSE: Autosomal recessive dedicator of cytokinesis 8 (DOCK8-/-) and autosomal dominant signal transducer and activator of transcription 3 (STAT3-/+) deficiencies are inborn errors of immunity (IEI) disorders present with the classic features of eczema and create a dilemma during differentiation from atopic dermatitis (AD). Therefore, an appropriate approach is required for eczema to diagnose DOCK8-/- and STAT3-/+ early. Here, we described a set of clinical and immunological variables, including atypical AD localizations and lymphocyte subsets, to differentiate DOCK8-/- or STAT3-/+ from AD. METHODS: This multicenter study involved 100 patients with DOCK8-/- and STAT3-/+ and moderate/severe AD. We recruited disease manifestations, including detailed localizations of eczema, infections, and allergy. Principle component analysis (PCA) was used to discriminate DOCK8-/- or STAT3-/+ from AD. RESULTS: There were 43 patients with DOCK8-/-, 23 with STAT3-/+, and 34 with AD. Pneumonia, severe infections, mucocutaneous candidiasis, and skin abscesses were commonly observed in DOCK8 and STAT3 deficiencies. Atypical skin involvement with neonatal rash, retro auricular, axillary, sacral, and genital eczema discriminate DOCK8-/- and STAT3-/+ from AD with high specificity ranges between 73.5 and 94.1% and positive predictive index ranges between 55 and 93.1%. Together with using absolute numbers of CD3+, CD4+, and CD8+ T cells, the combined clinical and laboratory features showed perfect differentiation between DOCK8-/- or STAT3-/+ and AD via PCA. CONCLUSIONS: The described features can be easily implemented by physicians providing early diagnosis of DOCK8 and STAT3 deficiencies.

Retrospective analysis of patients with severe combined immunodeficiency and alternative diagnostic criteria: A 20-year single centre experience.

Severe combined immunodeficiency (SCID) is an inborn errors of immunity (IEI) disorder characterized by impairment in the development and function of lymphocytes and could be fatal if not treated with hematopoietic stem cell transplant in the first 2 years of life. There are various diagnostic criteria for SCID among different primary immunodeficiency societies. We retrospectively evaluated clinical and laboratory findings of 59 patients followed up with the diagnosis of SCID at our clinic over the past 20 years in order to develop an algorithm that would help diagnosis of SCID for the countries where a high ratio of consanguineous marriage is present because these countries have not launched TREC assay in their newborn screening programs. The mean age at diagnosis was 5.80 ± 4.90 months, and the delay was 3.29 ± 3.99 months. The most common complaint and physical examination findings were cough (29.05%), eczematous rash (63%) and organomegaly (61%). ADA (17%), Artemis (14%), RAG1/2 (15%), MHC Class II (12%) and IL-2R (12%) deficiencies were the most common genetic defects. Lymphopenia (87.5%) was the most frequent abnormal laboratory finding and below 3000/mm3 in 95% of the patients. The CD3+ T cell count was 300/mm3 and below in 83% of the patients. As a result, a combination of low lymphocyte count and CD3 lymphopenia for SCID diagnosis would be more reliable for countries with high rate of consanguineous marriage. Physicians should consider diagnosis of SCID in a patient presenting with severe infections and lymphocyte counts below 3000/mm3 under 2 years of age.

Intraoral and maxillofacial abnormalities in patients with autosomal dominant hyper-IgE syndrome.

Autosomal dominant hyper-IgE syndrome (AD-HIES) is an inborn error of immunity (IEI) caused by a dominant-negative mutation in the signal transducer and activator of transcription 3 (STAT 3). This disease is characterized by chronic eczematoid dermatitis, recurrent staphylococcal skin abscesses, pneumonia, pneumatoceles, and extremely high serum IgE levels. Loss-of-function STAT3 mutations may also result in distinct non-immunologic features such as dental, facial, skeletal, and vascular abnormalities, central nervous system malformations and an increased risk for bone fractures. Prophylactic treatment of Candida infections and prophylactic antimicrobial therapy for staphylococcal skin infections and sinopulmonary infections are essential. An awareness of the oral and maxillofacial features of HIES may facilitate early diagnosis with genetic counselling and may improve future patient care. This study describes oral, dental, and maxillofacial manifestations in 14 patients with genetically defined AD-HIES. We also review the literature and propose recommendations for the complex care of patients with this rare primary immunodeficiency.

Long-Term Experience of Subcutaneous Immunoglobulin Therapy in Pediatric Primary Immunodeficient Patients with Low and Normal Body Weight.

PURPOSE: The aim was to review the compliance, side effects and effectiveness of subcutaneous immunoglobulin (SCIG) supplementation in patients with primary immunodeficiencies (PID) who had previously received intravenous immunoglobulin (IVIG) therapy and subsequently switched to SCIG, as well as to compare these parameters in patients while considering body weight. METHODS: Demographic data, clinical and laboratory findings, SCIG dose, and side effects of 87 patients were retrospectively obtained from patient files. In patients who first received IVIG and then SCIG, the monthly SCIG dose was calculated by multiplying the IVIG dose by 1.37. The total monthly SCIG dose was distributed via injection across three or four doses per month, thus every 7 or 10 days. RESULTS: Of the 87 patients aged between one and 22 years, 50 were male (57.5%) and 37 were female (42.5%). The serum IgG levels of the SCIG group were higher and more stable than those of the IVIG group. The number of hospitalizations and infections decreased significantly after initiation of SCIG. Thirteen patients (14.9%) had low body weight (LBW) for their age, seven of whom were male (53.8%). Serum IgG levels of the LBW cohort were significantly elevated and more stable during the SCIG period than the IVIG period. Mild, local side effects were detected in 153 administrations (3.3%) in 30 patients with normal body weight, while no local reactions were recorded in the patients with LBW. CONCLUSION: SCIG supplementation is an effective treatment for pediatric patients with PID. The preliminary data from the present study suggest that such treatment is also safe for LBW children. The numbers of patient hospitalizations and family visits to clinics were reduced, allowing our patients and their parents to live more normal lives.

Comparing the levels of CTLA-4-dependent biological defects in patients with LRBA deficiency and CTLA-4 insufficiency.

BACKGROUND: Lipopolysaccharide-responsive beige-like anchor protein (LRBA) deficiency and cytotoxic T-lymphocyte protein-4 (CTLA-4) insufficiency are recently described disorders that present with susceptibility to infections, autoimmunity, and lymphoproliferation. Clinical and immunological comparisons of the diseases with long-term follow-up have not been previously reported. We sought to compare the clinical and laboratory manifestations of both diseases and investigate the role of flow cytometry in predicting the genetic defect in patients with LRBA deficiency and CTLA-4 insufficiency. METHODS: Patients were evaluated clinically with laboratory assessments for lymphocyte subsets, T follicular helper cells (TFH ), LRBA expression, and expression of CD25, FOXP3, and CTLA4 in regulatory T cells (Tregs) at baseline and 16 h post-stimulation. RESULTS: LRBA-deficient patients (n = 29) showed significantly early age of symptom onset, higher rates of pneumonia, autoimmunity, chronic diarrhea, and failure to thrive compared to CTLA-4 insufficiency (n = 12). In total, 29 patients received abatacept with favorable responses and the overall survival probability was not different between transplanted versus non-transplanted patients in LRBA deficiency. Meanwhile, higher probability of survival was observed in CTLA-4-insufficient patients (p = 0.04). The T-cell subsets showed more deviation to memory cells in CTLA-4-insufficiency, accompanied by low percentages of Treg and dysregulated cTFH cells response in both diseases. Cumulative numbers of autoimmunities positively correlated with cTFH frequencies. Baseline CTLA-4 expression was significantly diminished in LRBA deficiency and CTLA-4 insufficiency, but significant induction in CTLA-4 was observed after short-term T-cell stimulation in LRBA deficiency and controls, while this elevation was less in CTLA-4 insufficiency, allowing to differentiate this disease from LRBA deficiency with high sensitivity (87.5%) and specificity (90%). CONCLUSION: This cohort provided detailed clinical and laboratory comparisons for LRBA deficiency and CTLA-4 insufficiency. The flow cytometric approach is useful in predicting the defective gene; thus, targeted sequencing can be conducted to provide rapid diagnosis and treatment for these diseases impacting the CTLA-4 pathway.

Memory B cells and serum immunoglobulins are associated with disease severity and mortality in patients with COVID-19.

PURPOSE OF THE STUDY: The aim of this study was to investigate the relationship of B cell-mediated immunity with disease severity and mortality in patients with COVID-19. STUDY DESIGN: In this retrospective cohort and single-centre study, 208 patients with laboratory-confirmed COVID-19 were recruited. A COVID-19 severity score, ranging from 0 to 10, was used to evaluate associations between various factors. Serum immunoglobulin levels and the number of cells in B lymphocyte subsets were measured and their association with disease severity and mortality in patients with COVID-19 examined. RESULTS: The median age of the patients was 50 (35-63) years and 88 (42%) were female. The number of deceased patients was 17. The median COVID-19 severity score was 8 (6-8) in deceased patients and 1 (0-2) in survivors. Deceased patients had significantly lower levels of total B lymphocytes, naive B cells, switched memory B cells, and serum IgA, IgG, IgG1 and IgG2 than recovered patients (all p<0.05). In addition, a significant negative correlation was found between the number of these parameters and COVID-19 severity scores. Decrease in the number of total B cells and switched memory B cells as well as lower serum IgA, IgG and IgG1 levels were independent risk factors for mortality in patients with COVID-19. CONCLUSION: In the present study, the prognosis of patients with COVID-19 was shown to be associated with the B cell subset and serum immunoglobulin levels.

Evaluation of immunological abnormalities in patients with rare syndromes.

Introduction: Recurrent infections are important problems in syndromic patients. This study aimed to evaluate immunological abnormalities in patients who presented with recurrent infections and were diagnosed with rare syndromes. Material and methods: This retrospective analysis included 14 patients with complaints of recurrent infections, all of whom were diagnosed with a rare syndrome. Results: The study group consisted of patients with Aicardi syndrome, Brugada syndrome, Phelan- McDermid syndrome, trichothiodystrophy, LEOPARD syndrome, Prader-Willi syndrome, Seckel syndrome, trisomy 18 (Edwards' syndrome), Wiedemann-Steiner syndrome, West syndrome, Williams syndrome, 47,XYY syndrome, 16p13 deletion syndrome, and 13q1.3 deletion syndrome. Seven patients (50%) were girls and seven (50%) were boys (mean age, 56.7 ±32.9 months; median [range] age: 45.5 [27-153] months). There were high rates of consanguinity (50%), cesarean section delivery (71%), and hospitalization in the intensive care unit (78.5%). No patients had a family history of immunodeficiency. On admission, all patients exhibited humoral and/or cellular immune system abnormalities. During the follow-up period, all T-cell abnormalities were improved after immunoglobulin replacement therapy (IGRT), while B-cell abnormalities persisted. These findings suggested that the patients predominantly had antibody deficiencies associated with mild T-cell abnormalities because of recurrent infections. The rates of infections and hospitalizations were significantly reduced after IGRT (p < 0.001); the rate of intensive care unit admission also significantly decreased (from 78.5% to 21.4%). Two of the three oxygen-dependent patients exhibited improvement therein. IGRT was discontinued in two patients with significant clinical improvement during follow-up. Conclusions: An immunological evaluation should be considered in pediatric patients with rare syndromes and recurrent infections. IGRT may help to improve the prognoses of these patients.

Single-Center Study of 72 Patients with Severe Combined Immunodeficiency: Clinical and Laboratory Features and Outcomes.

Severe combined immunodeficiency is an inborn error of immunity characterized by impairments in the numbers and functions of T and B lymphocytes due to various genetic causes, and if it remains untreated, patients succumb to infections during the first 2 years of life. PURPOSE AND METHODS: This study reported retrospective data from 72 infants diagnosed with SCID including their major clinical features, HSCT characteristics, and outcomes over a 20-year period (1997-2017). RESULTS: Sixty-one of 72 SCID patients in the study underwent HSCT from 1997 to 2017. Median ages at the time of diagnosis and transplantation were 3.5 months and 5 months, respectively. Consanguinity was present in 68% of the patients, and T - B - NK + phenotype was predominantly identified. The overall survival was 80.3% over a 20-year period. However, the patients transplanted during an active infection had a lower survival rate of 73.9% compared to 100% for patients transplanted infection-free or with a previous infection that had resolved. The survival rate was significantly higher among recipients of HLA-identical transplants (92.9%), compared to recipients of mismatched related transplants (70%). The overall survival increased from 50 (1997-2006) to 85% (2007-2017) during the last 10 years. CONCLUSIONS: This is one of the largest single-center studies in Turkey with extensive experience about SCID patients. Early diagnosis of SCID patients before the onset of an infection and early transplantation are shown to be extremely important factors affecting the outcome and increasing the survival regardless of the donor type based on the results of this study.

Consensus Middle East and North Africa Registry on Inborn Errors of Immunity.

BACKGROUND: Inborn errors of immunity (IEIs) are a heterogeneous group of genetic defects of immunity, which cause high rates of morbidity and mortality mainly among children due to infectious and non-infectious complications. The IEI burden has been critically underestimated in countries from middle- and low-income regions and the majority of patients with IEI in these regions lack a molecular diagnosis. METHODS: We analyzed the clinical, immunologic, and genetic data of IEI patients from 22 countries in the Middle East and North Africa (MENA) region. The data was collected from national registries and diverse databases such as the Asian Pacific Society for Immunodeficiencies (APSID) registry, African Society for Immunodeficiencies (ASID) registry, Jeffrey Modell Foundation (JMF) registry, J Project centers, and International Consortium on Immune Deficiency (ICID) centers. RESULTS: We identified 17,120 patients with IEI, among which females represented 39.4%. Parental consanguinity was present in 60.5% of cases and 27.3% of the patients were from families with a confirmed previous family history of IEI. The median age of patients at the onset of disease was 36 months and the median delay in diagnosis was 41 months. The rate of registered IEI patients ranges between 0.02 and 7.58 per 100,000 population, and the lowest rates were in countries with the highest rates of disability-adjusted life years (DALY) and death rates for children. Predominantly antibody deficiencies were the most frequent IEI entities diagnosed in 41.2% of the cohort. Among 5871 patients genetically evaluated, the diagnostic yield was 83% with the majority (65.2%) having autosomal recessive defects. The mortality rate was the highest in patients with non-syndromic combined immunodeficiency (51.7%, median age: 3.5 years) and particularly in patients with mutations in specific genes associated with this phenotype (RFXANK, RAG1, and IL2RG). CONCLUSIONS: This comprehensive registry highlights the importance of a detailed investigation of IEI patients in the MENA region. The high yield of genetic diagnosis of IEI in this region has important implications for prevention, prognosis, treatment, and resource allocation.

Simple Measurement of IgA Predicts Immunity and Mortality in Ataxia-Telangiectasia.

Patients with ataxia-telangiectasia (A-T) suffer from progressive cerebellar ataxia, immunodeficiency, respiratory failure, and cancer susceptibility. From a clinical point of view, A-T patients with IgA deficiency show more symptoms and may have a poorer prognosis. In this study, we analyzed mortality and immunity data of 659 A-T patients with regard to IgA deficiency collected from the European Society for Immunodeficiencies (ESID) registry and from 66 patients with classical A-T who attended at the Frankfurt Goethe-University between 2012 and 2018. We studied peripheral B- and T-cell subsets and T-cell repertoire of the Frankfurt cohort and survival rates of all A-T patients in the ESID registry. Patients with A-T have significant alterations in their lymphocyte phenotypes. All subsets (CD3, CD4, CD8, CD19, CD4/CD45RA, and CD8/CD45RA) were significantly diminished compared to standard values. Patients with IgA deficiency (n = 35) had significantly lower lymphocyte counts compared to A-T patients without IgA deficiency (n = 31) due to a further decrease of naïve CD4 T-cells, central memory CD4 cells, and regulatory T-cells. Although both patient groups showed affected TCR-ß repertoires compared to controls, no differences could be detected between patients with and without IgA deficiency. Overall survival of patients with IgA deficiency was significantly diminished. For the first time, our data show that patients with IgA deficiency have significantly lower lymphocyte counts and subsets, which are accompanied with reduced survival, compared to A-T patients without IgA deficiency. IgA, a simple surrogate marker, is indicating the poorest prognosis for classical A-T patients. Both non-interventional clinical trials were registered at clinicaltrials.gov 2012 (Susceptibility to infections in ataxia-telangiectasia; NCT02345135) and 2017 (Susceptibility to Infections, tumor risk and liver disease in patients with ataxia-telangiectasia; NCT03357978).

An association between immune status and chest CT scores in COVID-19 patients.

BACKGROUND: The characteristic features of the immune responses of COVID-19 patients and how they reflect lung involvement have not been clearly elucidated. AIM: The aim of this study was to examine the immune status and the correlations thereof with chest CT scores and lung involvement of patients with COVID-19. METHODS: In this retrospective and single-center study, 72 patients with laboratory-confirmed COVID-19 were recruited. The counts of peripheral lymphocyte subsets (CD3+ T cells, CD4+ T cells, CD8+ T cells, CD19+ B cells and CD16+ 56+ NK cells) and those of serum immunoglobulins (IgA, IgG, IgM) were measured and their associations with chest CT scores analysed. RESULTS: The proportions of lymphopenia in patients with extensive lung involvement were twice that in the general study population. In the severe disease group, the levels of total lymphocytes, T cells, B cells, NK cells; and serum IgA levels, were significantly lower than in the mild disease group (all P < .05). We found that the numbers of lymphocyte subsets and the IgA level negatively correlated with the chest CT scores. On multivariate regression analysis, pretreatment decreases in total lymphocytes, CD3+ T cells, CD4+ T cells, and CD19+ B cells, and serum IgA levels, were independent predictors of severe lung involvement. CONCLUSIONS: The cell numbers of peripheral lymphocyte subsets and the serum IgA level were negatively correlated with the chest CT scores in COVID-19 patients. These parameters tended to independently predict severe lung involvement in such patients.

Combined immunodeficiency caused by a loss-of-function mutation in DNA polymerase delta 1.

BACKGROUND: Mutations affecting DNA polymerases have been implicated in genomic instability and cancer development, but the mechanisms by which they can affect the immune system remain largely unexplored. OBJECTIVE: We sought to establish the role of DNA polymerase δ1 catalytic subunit (POLD1) as the cause of a primary immunodeficiency in an extended kindred. METHODS: We performed whole-exome and targeted gene sequencing, lymphocyte characterization, molecular and functional analyses of the DNA polymerase δ (Polδ) complex, and T- and B-cell antigen receptor repertoire analysis. RESULTS: We identified a missense mutation (c. 3178C>T; p.R1060C) in POLD1 in 3 related subjects who presented with recurrent, especially herpetic, infections and T-cell lymphopenia with impaired T-cell but not B-cell proliferation. The mutation destabilizes the Polδ complex, leading to ineffective recruitment of replication factor C to initiate DNA replication. Molecular dynamics simulation revealed that the R1060C mutation disrupts the intramolecular interaction between the POLD1 CysB motif and the catalytic domain and also between POLD1 and the Polδ subunit POLD2. The patients exhibited decreased numbers of naive CD4 and especially CD8 T cells in favor of effector memory subpopulations. This skewing was associated with oligoclonality and restricted T-cell receptor ß-chain V-J pairing in CD8+ but not CD4+ T cells, suggesting that POLD1R1060C differentially affects peripheral CD8+ T-cell expansion and possibly thymic selection. CONCLUSION: These results identify gene defects in POLD1 as a novel cause of T-cell immunodeficiency.

Spatiotemporal Gradient of Cortical Neuron Death Contributes to Microcephaly in Knock-In Mouse Model of Ligase 4 Syndrome.

Cells of the developing central nervous system are particularly susceptible to formation of double-stranded DNA breaks (DSBs) arising from physiological and/or environmental insults. Therefore, efficient repair of DSBs is especially vital for maintaining cellular health and proper functioning in the developing brain. Here, increased expression of DSB initiating and nonhomologous end joining repair machinery in newborn neurons in the developing brains of both mouse and human are demonstrated. In parallel, the first characterization is provided of the brain phenotype in the Lig4R278H/R278H (Lig4R/R) mouse model of DNA Ligase 4 (LIG4) syndrome, in which a hypomorphic Lig4 mutation, originally identified in patients, impedes nonhomologous end joining. It is shown that Lig4R/R mice develop nonprogressive microcephaly, resulting primarily from apoptotic death of newborn neurons that is both spatially and temporally specific during peak cortical neurogenesis. This apoptosis leads to a reduction in neurons throughout the postnatal cerebral cortex, but with a more prominent impact on those of the lower cortical layers. Together, these findings begin to uncover the pathogenesis of microcephaly in LIG4 syndrome and open avenues to more focused investigations on the critical roles of DSB formation and repair in vulnerable neuronal populations of the brain.

Patients with CD3G mutations reveal a role for human CD3γ in Treg diversity and suppressive function.

Integrity of the T-cell receptor/CD3 complex is crucial for positive and negative selection of T cells in the thymus and for effector and regulatory functions of peripheral T lymphocytes. In humans, CD3D, CD3E, and CD3Z gene defects are a cause of severe immune deficiency and present early in life with increased susceptibility to infections. By contrast, CD3G mutations lead to milder phenotypes, mainly characterized by autoimmunity. However, the role of CD3γ in establishing and maintaining immune tolerance has not been elucidated. In this manuscript, we aimed to investigate abnormalities of T-cell repertoire and function in patients with genetic defects in CD3G associated with autoimmunity. High throughput sequencing was used to study composition and diversity of the T-cell receptor ß (TRB) repertoire in regulatory T cells (Tregs), conventional CD4+ (Tconv), and CD8+ T cells from 6 patients with CD3G mutations and healthy controls. Treg function was assessed by studying its ability to suppress proliferation of Tconv cells. Treg cells of patients with CD3G defects had reduced diversity, increased clonality, and reduced suppressive function. The TRB repertoire of Tconv cells from patients with CD3G deficiency was enriched for hydrophobic amino acids at positions 6 and 7 of the CDR3, a biomarker of self-reactivity. These data demonstrate that the T-cell repertoire of patients with CD3G mutations is characterized by a molecular signature that may contribute to the increased rate of autoimmunity associated with this condition.

ILC3 deficiency and generalized ILC abnormalities in DOCK8-deficient patients.

BACKGROUND: Dedicator of cytokinesis 8 (DOCK8) deficiency is the main cause of the autosomal recessive hyper-IgE syndrome (HIES). We previously reported the selective loss of group 3 innate lymphoid cell (ILC) number and function in a Dock8-deficient mouse model. In this study, we sought to test whether DOCK8 is required for the function and maintenance of ILC subsets in humans. METHODS: Peripheral blood ILC1-3 subsets of 16 DOCK8-deficient patients recruited at the pretransplant stage, and seven patients with autosomal dominant (AD) HIES due to STAT3 mutations, were compared with those of healthy controls or post-transplant DOCK8-deficient patients (n = 12) by flow cytometry and real-time qPCR. Sorted total ILCs from DOCK8- or STAT3-mutant patients and healthy controls were assayed for survival, apoptosis, proliferation, and activation by IL-7, IL-23, and IL-12 by cell culture, flow cytometry, and phospho-flow assays. RESULTS: DOCK8-deficient but not STAT3-mutant patients exhibited a profound depletion of ILC3s, and to a lesser extent ILC2s, in their peripheral blood. DOCK8-deficient ILC1-3 subsets had defective proliferation, expressed lower levels of IL-7R, responded less to IL-7, IL-12, or IL-23 cytokines, and were more prone to apoptosis compared with those of healthy controls. CONCLUSION: DOCK8 regulates human ILC3 expansion and survival, and more globally ILC cytokine signaling and proliferation. DOCK8 deficiency leads to loss of ILC3 from peripheral blood. ILC3 deficiency may contribute to the susceptibility of DOCK8-deficient patients to infections.