Maturational alterations of peripheral T cell subsets and cytokine gene expression in 22q11.2 deletion syndrome

Chromosome 22q11.2 deletion syndrome is a common disorder characterized by thymic hypoplasia, conotruncal cardiac defect and hypoparathyroidism. Patients have a risk of infections and autoimmunity associated with T lymphocytopenia. To assess the immunological constitution of patients, the numerical changes and cytokine profile of circulating T cells were analysed by flow cytometry and real-time polymerase chain reaction (PCR). CD3+, CD4+, T cell receptor (TCR)alphabeta+ or CD8alphaalpha+ cell counts were lower, and CD56+ cell counts were higher in patients than in controls during the period from birth to adulthood. The ageing decline of CD3+ or CD4+ cell counts was slower in patients than in controls. The proportion of CD8alphaalpha+ cells increased in controls, and the slope index was larger than in patients. On the other hand, both the number and proportion of Valpha24+ cells increased in patients, and the slope indexes tended to be larger than in controls. The positive correlation of the number of T cells with CD8alphaalpha+ cells was observed only in patients, and that with Valpha24+ cells was seen only in controls. No gene expression levels of interferon (IFN)-gamma, interleukin (IL)-10, transforming growth factor (TGF)-beta, cytotoxic T lymphocyte antigen 4 (CTLA4) or forkhead box p3 (Foxp3) in T cells differed between patients and controls. There was no significant association between the lymphocyte subsets or gene expression levels and clinical phenotype including the types of cardiac disease, hypocalcaemia and frequency of infection. These results indicated that T-lymphocytopenia in 22q11.2 deletion patients became less severe with age under the altered composition of minor subsets. The balanced cytokine profile in the limited T cell pool may represent a T cell homeostasis in thymic deficiency syndrome.     

Lack of Correlation between Impaired T Cell Production,Immunodeficiency, and Other Phenotypic Features in Chromosome 22q11.2 Deletion Syndromes (DiGeorge Syndrome/Velocardiofacial Syndrome)

Monosomic deletions of chromosome 22q11.2 are the leading cause of DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome. DiGeorge syndrome was originally described as an immunodeficiency disorder secondary to impaired T cell production due to thymic aplasia or hypoplasia; however, the frequency of immunodeficiency in the other clinical syndromes associated with the chromosome 22q11.2 microdeletion has not been previously investigated. This study examines the frequency and severity of impaired T cell production and immunodeficiency in chromosome 22q11.2 deletion syndromes and the relationship of the immunodeficiency to specific phenotypic features. Sixty patients over 6 months of age with the characteristic chromosome 22q11.2 deletion underwent immunologic evaluations. Seventy-seven percent of patients with chromosome 22q11.2 deletions were found to have evidence of immunocompromise. The severity of the immunodeficiency did not correlate with any particular phenotypic feature, nor was it restricted to patients who were categorized as having DiGeorge syndrome. Therefore, impaired T cell production and impaired immunologic function are common in patients with deletions of chromosome 22q11.2. The presence or severity of the immunocompromise cannot be predicted based on other phenotypic features and each child should be individually assessed for immune function.     

Chromatin Modifications in 22q11.2 Deletion Syndrome

Journal of Clinical Immunology - Chromosome 22q11.2 deletion syndrome is a common inborn error of immunity. The early consequences of thymic hypoplasia are low T cell numbers. Later in life, atopy,...     

Immunologic reconstitution in 22q deletion (DiGeorge) syndrome

Adoptive transfer of mature T cells (ATMTC) through bone marrow (BM) transplantation, first attempted over 20 years ago, has recently emerged as a successful therapy for complete 22q deletion syndrome (22qDS). This provides a potential option to thymic transplantation (TT) for immune reconstitution in 22qDS. Compared to thymic transplant, ATMTC is an easier procedure to accomplish and is available at more centers. However, there are differences in the nature of the T-cell reconstitution that results. Predictably, more naïve T cells and recent thymic emigrants are present in patients treated with thymus transplant. There are no significant differences in mortality between the two procedures, but the number of patients is too limited to conclude that the procedures are equally effective. Adoptive transfer should be pursued as a reasonable treatment for 22qDS patients requiring immune reconstitution when thymus transplant is not available.     

Biased T-cell receptor repertoires in patients with chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion (del22q11.2) syndrome (DiGeorge syndrome/velocardiofacial syndrome) is a common syndrome typically consisting of congenital heart disease, hypoparathyroidism, developmental delay and immunodeficiency. Although a broad range of immunologic defects have been described in these patients, limited information is currently available on the diversity of the T-cell receptor (TCR) variable beta (BV) chain repertoire. The TCRBV repertoires of nine patients with del22q11.2 syndrome were determined by flow cytometry, fragment size analysis of the third complementarity determining region (CDR3 spectratyping) and sequencing of V(D)J regions. The rate of thymic output and the phenotype and function of peripheral T cells were also studied. Expanded TCRBV families were detected by flow cytometry in both CD4+ and CD8+ T cells. A decreased diversity of TCR repertoires was also demonstrated by CDR3 spectratyping, showing altered CDR3 profiles in the majority of TCRBV families investigated. The oligoclonal nature of abnormal peaks detected by CDR3 spectratyping was confirmed by the sequence analysis of the V(D)J regions. Thymic output, evaluated by measuring TCR rearrangement excision circles (TRECs), was significantly decreased in comparison with age-matched controls. Finally, a significant up-regulation in the percentage, but not in the absolute count, of activated CD4+ T cells (CD95+, CCR5+, HLA-DR+), IFN-gamma - and IL-2-expressing T cells was detected. These findings suggest that the diversity of CD4 and CD8 TCRBV repertoires is decreased in patients with del22q11.2 syndrome, possibly as a result of either impaired thymic function and/or increased T-cell activation.     

Chromosome 22q11.2 deletion syndrome and DiGeorge syndrome

Chromosome 22q11.2 deletion syndrome is the most common microdeletion syndrome in humans. The effects are protean and highly variable, making a unified approach difficult. Nevertheless, commonalities have been identified and white papers with recommended evaluations and anticipatory guidance have been published. This review will cover the immune system in detail and discuss both the primary features and the secondary features related to thymic hypoplasia. A brief discussion of the other organ system involvement will be provided for context. The immune system, percolating throughout the body can impact the function of other organs through allergy or autoimmune disease affecting organs in deleterious manners. Our work has shown that the primary effect of thymic hypoplasia is to restrict T cell production. Subsequent homeostatic proliferation and perhaps other factors drive a Th2 polarization, most obvious in adulthood. This contributes to atopic risk in this population. Thymic hypoplasia also contributes to low regulatory T cells and this may be part of the overall increased risk of autoimmunity. Collectively, the effects are complex and often age‐dependent. Future goals of improving thymic function or augmenting thymic volume may offer a direct intervention to ameliorate infections, atopy, and autoimmunity.     

Low thymic output in the 22q11.2 deletion syndrome measured by CCR9+CD45RA+ T cell counts and T cell receptor rearrangement excision circles

Thymic hypoplasia is a frequent feature of the 22q11.2 deletion syndrome, but we know little about patients' age‐related thymic output and long‐term consequences for their immune system. We measured the expression of T cell receptor rearrangement excision circles (TREC) and used flow cytometry for direct subtyping of recent thymic emigrant (RTE)‐related T cells in 43 patients (aged 1–54 years; median 9 years) from all over Norway and in age‐matched healthy controls. Thymic volumes were estimated by ultrasound in patients. TREC levels correlated well with RTE‐related T cells defined by co‐expression of CD3, CD45RA and CCR9 (r = 0·84) as well as with the CD4⁺ and CD8⁺ T cell subtypes. RTE‐related T cell counts also paralleled age‐related TREC reductions. CD45RA⁺ T cells correlated well with absolute counts of CD4⁺ (r = 0·87) and CD8⁺ (r = 0·75) RTE‐related T cells. Apart from CD45RA^‐ T cells, all T cell subsets were lower in patients than in controls. Thymic volumes correlated better with RTE‐related cells (r = 0·46) than with TREC levels (r = 0·38). RTE‐related T cells and TREC levels also correlated well (r = 0·88) in patients without an identifiable thymus. Production of RTEs is impaired in patients with a 22q11.2 deletion, and CCR9 appears to be a good marker for RTE‐related T cells.     

CD4(+) CD25(+) T-cell production in healthy humans and in patients with thymic hypoplasia

Regulatory T cells are found primarily in the CD4(+) CD25(+) fraction of T cells and play an important role in the prevention of autoimmunity. We examined CD4(+) CD25(+) T cells in 33 healthy children and adults and compared them to a population with an inherited form of thymic hypoplasia and a predisposition to autoimmune disease. Absolute numbers of CD4(+) CD25(+) T cells were markedly higher in healthy infants than in infants with chromosome 22q11.2 deletion syndrome.     

A Prospective Study of Influenza Vaccination and a Comparison of Immunologic Parameters in Children and Adults with Chromosome 22q11.2 Deletion Syndrome (DiGeorge Syndrome/Velocardiofacial Syndrome)

Prior to the advent of cardiac bypass, most children with congenital cardiac anomalies and chromosome 22q11.2 deletion syndrome died. With improved technology, there is now a wave of young adults with chromosome 22q11.2 deletion syndrome requiring clinical care. Fifteen young children and 20 adults with chromosome 22q11.2 deletion had flow cytometry, functional T cell analyses, and functional B cell analyses to characterize their immune system. Subjects were vaccinated with the annual inactivated influenza vaccine, and responses were evaluated by hemagglutination inhibition titer assessment. The pattern of T cell subset abnormalities was markedly different between pediatric and adult patients. In spite of the cellular deficits observed in adults, titers produced after influenza vaccine administration were largely intact. We conclude that disruption to T cell production appears to have secondary consequences for T cell differentiation and B cell function although the clinical impact remains to be determined.     

T cell receptor repertoire and function in patients with DiGeorge syndrome and velocardiofacial syndrome

DiGeorge syndrome (DGS) and velocardiofacial syndrome (VCFS) are associated with chromosome 22q11.2 deletion. Limited information is available on the T cell receptor (TCR) Vbeta repertoire. We therefore investigated TCR Vbeta families in lymphocytes isolated from blood and thymic samples of seven patients with DGS and seven patients with VCFS, all with 22q11.2 deletion. We also studied activities related to TCR signalling including in vitro proliferation, anti-CD3-induced protein tyrosine phosphorylation, and susceptibility to apoptosis. Reduced CD3+ T cells were observed in most patients. Spontaneous improvement of T cell numbers was detected in patients, 3 years after the first study. Analysis of CD4+ and CD8+ TCR Vbeta repertoire in peripheral and thymic cells showed a normal distribution of populations even if occasional deletions were observed. Lymphoproliferative responses to mitogens were comparable to controls as well as anti-CD3-induced protein tyrosine phosphorylation. Increased anti-CD3-mediated apoptosis was observed in thymic cells. Our data support the idea that in patients surviving the correction of cardiac anomalies, the immune defect appears milder than originally thought, suggesting development of a normal repertoire of mature T cells.     

The clinical, immunological, and molecular spectrum of chromosome 22q11.2 deletion syndrome and DiGeorge syndrome

PURPOSE OF REVIEW: New findings regarding the clinical manifestations and care of patients with DiGeorge syndrome or chromosome 22q11.2 deletion syndrome will be reviewed. Immunologists and primary care providers often are in a position to coordinate the complex care needs of these patients and an awareness of the clinical features is essential. RECENT FINDINGS: DiGeorge syndrome typically occurs in association with a hemizygous deletion of chromosome 22q11.2. Approximately 5-10% of patients with the clinical entity of DiGeorge syndrome do not have the deletion. Recent evidence indicates that the T cell compartment in both patients with the deletion and patients with clinical DiGeorge syndrome without the deletion is less robust than is often indicated by standard T cell enumeration. SUMMARY: This past year has seen a dramatic increase in our understanding of the clinical features of patients with the deletion. Advances in our understanding of the immunodeficiency have been particularly exciting and clinicians should be aware of the characteristics of the immunodeficiency and its changes with age.     

DiGeorge anomaly in a patient with isochromosome 18p born to a diabetic mother

The DiGeorge anomaly (DGA) is an etiologically heterogeneous developmental field defect in which cardiovascular malformations, hypocalcemia, thymic hypoplasia, and characteristic dysmorphisms are major clinical features. The 22q11.2 deletion is the most common single etiology of DGA, although a number of other chromosomal abnormalities and teratogens, including maternal diabetes, have been implicated as well. We present a patient, born to a diabetic mother, with interrupted aortic arch type B (IAA-B), neonatal hypocalcemia, thymic hypoplasia, and dysmorphic features including microcephaly, thick, overfolded helices, and anteriorly-placed anus. Cytogenetic studies showed the presence of a marker chromosome, identified by fluorescence in-situ hybridization (FISH) as an isochromosome 18p [i(18p)]. We did not detect a 22q11.2 deletion by FISH using a cosmid probe corresponding to locus D22S75. The patient is the first example of either DGA or IAA-B in a patient with i(18p). We review the genetic abnormalities associated with DGA, and discuss the potential contributions of maternal diabetes and i(18p) in our patient.     

Increased Levels of Interferon‐Inducible Protein 10 (IP‐10) in 22q11.2 Deletion Syndrome

The 22q11.2 deletion syndrome (22q11.2 DS), also known as DiGeorge syndrome, is a genetic disorder with an estimated incidence of 1:4000 births. These patients may suffer from affection of many organ systems with cardiac malformations, thymic hypoplasia or aplasia, hypoparathyroidism, palate anomalies and psychiatric disorders being the most frequent. The incidence of autoimmune diseases is increased in older patients. The aim of the present study was to examine a cytokine profile in patients with 22q11.2 DS by measuring a broad spectrum of serum cytokines. Patients with a proven deletion of chromosome 22q11.2 (n = 55) and healthy individuals (n = 54) recruited from an age‐ and sex‐comparable group were included in the study. Serum levels of 27 cytokines, including chemokines and growth factors, were analysed using multiplex technology. Interferon‐inducible protein 10 (IP‐10) was also measured by ELISA to confirm the multiplex results. The 22q11.2 DS patients had distinctly and significantly raised levels of pro‐inflammatory and angiostatic chemokine IP‐10 (P < 0.001) compared to controls. The patients with congenital heart defects (n = 31) had significantly (P = 0.018) raised serum levels of IP‐10 compared to patients born without heart defects (n = 24). The other cytokines investigated were either not detectable or did not differ between patients and controls.     

Vitamin D status and the immune assessment in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is characterized by a heterogeneous phenotype, including alterations in phospho-calcium metabolism and immunodeficiency. We analyzed vitamin D status and the immune assessment, focusing on T cell subpopulations and dendritic cells (DCs) in a cohort of 17 pediatric 22q11.2DS patients and 17 age-matched healthy subjects. As antigen-presenting cells, DCs are the main target of vitamin D, promoting a tolerogenic T cell response. Patients were subdivided into three groups according to the parameters of phospho-calcium metabolism and serum levels of 25OHD: normal values, vitamin D deficiency and hypoparathyroidism. Different degrees of T cell deficiency, ranging from normal to partial T cell numbers, were observed in the cohort of patients. The group with vitamin D deficiency showed a significant reduction of naive T cells and a significant increase of central memory T cells compared to controls. In this group the number of circulating DCs was significantly reduced. DC decrease affected both myeloid and plasmacytoid DC subsets (mDCs and pDCs), with the most relevant reduction involving pDCs. A direct correlation between 25OHD levels and recent thymic emigrant (RTE) and DC number was identified. Despite the limited cohort analyzed, our results show that deficiency of the pDC subset in patients with 22q11.2DS may be included among the causative factors of the progressive increase of risk of autoimmune diseases in these patients. As most patients suffer from increased susceptibility to infections and heightened prevalence of autoimmune disorders, we suggest a potential role of vitamin D supplementation in preventing autoimmune or proinflammatory diseases in 22q11.2DS.     

Microdeletion and microduplication 22q11.2 screening in 295 patients with clinical features of DiGeorge/Velocardiofacial syndrome

The 22q11.2 region is susceptible to chromosomal rearrangements, leading to various types of congenital malformation and mental retardation. The most common anomaly is 22q11.2 microdeletion, associated with DiGeorge/Velocardiofacial syndrome (DG/VCFS). Recently the microduplication 22q11.2 syndrome has been identified. Some clinical features in patients with this new chromosomal disorder present a substantial overlap with DG/VCFS. The aim of this hospital-based study was to evaluate the incidence of deletions and duplications on 22q11.2 in patients with DG/VCFS features. We investigated a group of 295 patients with widely variable manifestations associated with DG/VCFS. Along with the clinical diagnoses different anomalies were noted such as conotruncal cardiac anomaly, velopharyngeal insufficiency, characteristic facial dysmorphic features, language impairment, developmental delay/learning difficulties, and immunologic anomalies or thymic hypoplasia. Laboratory studies included conventional cytogenetic and FISH testing. Metaphase and interphase cells were analyzed for the presence of 22q11.2 microdeletion or microduplication. There were 12 patients who carried 22q11.2 microdeletion and no microduplication in the region was identified. Other chromosomal anomalies were reported in five patients with an overlapped DG/VCFS phenotype. All patients with 22q11.2 microdeletion showed a characteristic phenotype of DG/VCFS. We did not identify 22q11.2 microduplication, suggesting that this is a rare event in patients with DG/VCFS features.     

Longitudinal Analysis of Lymphocyte Function and Numbers in the First Year of Life in Chromosome 22q11.2 Deletion Syndrome (DiGeorge Syndrome/Velocardiofacial Syndrome)

Chromosome 22q11.2 deletion syndrome is a common syndrome typically consisting of variable cardiac defects, hypoparathyroidism, developmental delay, and immunodeficiency. The hemizygous deletion has variable effects on the immune system even within the same kindred, and the extent of the immunodeficiency is difficult to predict. Some patients have shown improvement over time; however, this is the first prospective longitudinal study of the dynamic nature of the immunodeficiency. Nineteen patients were studied prospectively between 1994 and 1997. The results of the newborn immunologic studies in the chromosome 22q11.2 deletion group were significantly different from those of a group of newborns with cardiac disease due to other causes. Peripheral blood T-cell numbers were decreased in the chromosome 22q11.2 deletion group, although T-cell function was largely preserved. The group as a whole demonstrated few changes in the first year of life, but a subset of patients with markedly diminished T-cell numbers did demonstrate improvement. Therefore, improvement in peripheral blood T-cell counts is variable in chromosome 22q11.2 deletion syndrome. The patients with the lowest T-cell counts improved the most in the first year of life.     

Longitudinal analysis of lymphocyte function and numbers in the first year of life in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome).

Chromosome 22q11.2 deletion syndrome is a common syndrome typically consisting of variable cardiac defects, hypoparathyroidism, developmental delay, and immunodeficiency. The hemizygous deletion has variable effects on the immune system even within the same kindred, and the extent of the immunodeficiency is difficult to predict. Some patients have shown improvement over time; however, this is the first prospective longitudinal study of the dynamic nature of the immunodeficiency. Nineteen patients were studied prospectively between 1994 and 1997. The results of the newborn immunologic studies in the chromosome 22q11.2 deletion group were significantly different from those of a group of newborns with cardiac disease due to other causes. Peripheral blood T-cell numbers were decreased in the chromosome 22q11.2 deletion group, although T-cell function was largely preserved. The group as a whole demonstrated few changes in the first year of life, but a subset of patients with markedly diminished T-cell numbers did demonstrate improvement. Therefore, improvement in peripheral blood T-cell counts is variable in chromosome 22q11.2 deletion syndrome. The patients with the lowest T-cell counts improved the most in the first year of life.     

Palatal evaluation and treatment in 22q11.2 deletion syndrome

Palatal involvement occurs commonly in patients with 22q11.2 Deletion Syndrome (22qDS), and includes palatal clefting and velopharyngeal dysfunction in the absence of overt or submucous clefts. The reported incidence and distribution of palatal abnormalities vary in the literature. The aim of this article is to revisit the incidence and presenting features of palatal abnormalities in a large cohort of patients with 22qDS, summarize the surgical treatments performed in this cohort, and provide an overview of surgical treatment protocols and management guidelines for palatal abnormalities in this syndrome. Charts of 1,121 patients seen through the 22q and You Center at the Children's Hospital of Philadelphia were reviewed for palatal status, demographic factors, deletion size, and corrective surgical procedures. Statistical analysis was performed using Pearson's chi‐squared test to identify differences between gender, deletion size, and palatal abnormality. Of the patients with complete evaluations, 67% were found to have a palatal abnormality. The most common finding was velopharyngeal dysfunction in 55.2% of patients, and in 33.3% of patients, this occurred in the absence of palatal clefting. There was no significant difference in the incidence of palatal abnormalities by gender; however, a difference was noted among race (p < 0.01) and deletion sizes (p < 0.01). For example, Caucasian and Asian patients presented with a much higher prevalence of palatal abnormalities, and conversely those with nested deletions presented with a much lower rate of palatal defects. Overall, 26.9% of patients underwent palatal surgery, and the most common indication was velopharyngeal dysfunction. Palatal abnormalities are a hallmark feature of 22q11.2 Deletion Syndrome; understanding the incidence, presenting features, and treatment protocols are essential for practitioners counseling and treating families affected with this disorder.     

Platelet findings in 22q11.2 deletion syndrome correlate with disease manifestations but do not correlate with GPIb surface expression

Prior studies have demonstrated that patients with chromosome 22q11.2 deletion syndrome (22q11.2DS) have lower platelet counts (PC) compared to non-deleted populations. They also have an increased mean platelet volume. The mechanism for this has been postulated to be haploinsufficiency of the GPIBB gene. We examined platelet parameters, deletion size and factors known to influence counts, including status of thyroid hormone and congenital heart disease (CHD), in a population of 825 patients with 22q11.2DS. We also measured surface expression of GPIB-IX complex by flow cytometry. The major determinant of PC was deletion status of GP1BB, regardless of surface expression or other factors. Patients with nested distal chromosome 22q11.2 deletions (those with GP1BB present) had higher PCs than those with proximal deletions where GP1BB is deleted. Patients with 22q11.2DS also demonstrated an accelerated PC decrease with age, occurring in childhood. These data demonstrate that genes within the proximal deletion segment drive PC differences in 22q11.2DS and suggest that PC reference ranges may need to be adjusted for age and deletion size in 22q11.2DS populations. Bleeding did not correlate with either platelet count or GPIb expression. Further studies into drivers of expression of GPIb and associations with severe thrombocytopenia and immune thrombocytopenia are needed to inform clinical care.