Age-related changes in humoral and cell-mediated immunity in Down syndrome children living at home

Down syndrome, accelerated aging and immunosenescence

Down syndrome is the most common chromosomal disorder, associated with moderate to severe intellectual disability. While life expectancy of Down syndrome population has greatly increased over the last decades, mortality rates are still high and subjects are facing prematurely a phenomenon of atypical and accelerated aging. The presence of an immune impairment in Down syndrome subjects is suggested for a long time by the existence of an increased incidence of infections, the incomplete efficacy of vaccinations, and a high prevalence of autoimmunity. Immunologic abnormalities have been described since many years in this population, both from a numerical and a functional points of view, and these abnormalities can mirror the ones observed during normal aging. In this review, we summarize our knowledge on immunologic disturbances commonly observed in subjects with Down syndrome, and in innate and adaptive immunity, as well as regarding chronic inflammation. We then discuss the role of accelerated aging in these observed abnormalities and finally review the potential age-associated molecular and cellular mechanisms involved.

Methylomic profiling in trisomy 21 identifies cognition- and Alzheimer's disease-related dysregulation

Abstract

Background

Trisomy 21 (T21) is associated with intellectual disability that ranges from mild to profound with an average intellectual quotient of around 50. Furthermore, T21 patients have a high risk of developing Alzheimer’s disease (AD) early in life, characterized by the presence of senile plaques of amyloid protein and neurofibrillary tangles, leading to neuronal loss and cognitive decline. We postulate that epigenetic factors contribute to the observed variability in intellectual disability, as well as at the level of neurodegeneration seen in T21 individuals.

Materials and Methods

A genome-wide DNA methylation study was performed using Illumina Infinium® MethylationEPIC BeadChips on whole blood DNA of 3 male T21 patients with low IQ, 8 T21 patients with high IQ (4 males and 4 females), and 21 age- and sex-matched control samples (12 males and 9 females) in order to determine whether DNA methylation alterations could help explain variation in cognitive impairment between individuals with T21. In view of the increased risk of developing AD in T21 individuals, we additionally investigated the T21-associated sites in published blood DNA methylation data from the AgeCoDe cohort (German study on Ageing, Cognition, and Dementia). AgeCoDe represents a prospective longitudinal study including non-demented individuals at baseline of which a part develops AD dementia at follow-up.

Results

Two thousand seven hundred sixteen differentially methylated sites and regions discriminating T21 and healthy individuals were identified. In the T21 high and low IQ comparison, a single CpG located in the promoter of PELI1 was differentially methylated after multiple testing adjustment. For the same contrast, 69 differentially methylated regions were identified. Performing a targeted association analysis for the significant T21-associated CpG sites in the AgeCoDe cohort, we found that 9 showed significant methylation differences related to AD dementia, including one in the ADAM10 gene. This gene has previously been shown to play a role in the prevention of amyloid plaque formation in the brain.

Conclusion

The differentially methylated regions may help understand the interaction between methylation alterations and cognitive function. In addition, ADAM10 might be a valuable blood-based biomarker for at least the early detection of AD.

Down Syndrome, Ageing and Epigenetics

During the past decades, life expectancy of subjects with Down syndrome (DS) has greatly improved, but age-specific mortality rates are still important and DS subjects are characterized by an acceleration of the ageing process, which affects particularly the immune and central nervous systems. In this chapter, we will first review the characteristics of the ageing phenomenon in brain and in immune system in DS and we will then discuss the biological hallmarks of ageing in this specific population. Finally, we will also consider in detail the knowledge on epigenetics in DS, particularly DNA methylation.

Systematic review and meta-analysis shows a specific micronutrient profile in people with Down Syndrome: Lower blood calcium, selenium and zinc, higher red blood cell copper and zinc, and higher salivary calcium and sodium

Different metabolic profiles as well as comorbidities are common in people with Down Syndrome (DS). Therefore it is relevant to know whether micronutrient levels in people with DS are also different. This systematic review was designed to review the literature on micronutrient levels in people with DS compared to age and sex-matched controls without DS. We identified sixty nine studies from January 1967 to April 2016 through main electronic medical databases PubMed, Scopus, and Web of knowledge. We carried out meta-analysis of the data on four essential trace elements (Cu, Fe, Se, and Zn), six minerals (Ca, Cl, K, Mg, Na, and P), and five vitamins (vitamin A, B9, B12, D, and E). People with DS showed lower blood levels of Ca (standard mean difference (SMD) = -0.63; 95% confidence interval (CI): -1.16 to -0.09), Se (SMD = -0.99; 95% CI: -1.55 to -0.43), and Zn (SMD = -1.30; 95% CI: -1.75 to -0.84), while red cell levels of Zn (SMD = 1.88; 95% CI: 0.48 to 3.28) and Cu (SMD = 2.77; 95% CI: 1.96 to 3.57) were higher. They had also higher salivary levels of Ca (SMD = 0.85; 95% CI: 0.38 to 1.33) and Na (SMD = 1.04; 95% CI: 0.39 to 1.69). Our findings that micronutrient levels are different in people with DS raise the question whether these differences are related to the different metabolic profiles, the common comorbidities or merely reflect DS.

Immunodeficiencies Associated with Abnormal Newborn Screening for T Cell and B Cell Lymphopenia

Newborn screening for SCID has revealed the association of low T cells with a number of unexpected syndromes associated with low T cells, some of which were not appreciated to have this feature. This review will discuss diagnostic approaches and the features of some of the syndromes likely to be encountered following newborn screening for immune deficiencies.

A comparison of salivary IgA in children with Down syndrome and their family members

The aim of this study was to compare total IgA in the whole saliva of children with Down syndrome with levels in sibling and parent groups. IgA measurements were presented as the concentration in saliva (μg/ml) and also adjusted for salivary flow rate (SFR; μg/min). Twenty children with Down syndrome, ten siblings and twenty parents were recruited. Stimulated whole saliva was collected from the participants and SFR calculated. The measurement of salivary IgA (sIgA) was carried out using an indirect competitive Enzyme-Linked Immunosorbent Assay. The difference in the mean SFR between children with Down syndrome, parents and siblings were not statistically significant. The mean salivary concentration of IgA was higher in children with Down syndrome (95.1 μg/ml) compared with siblings (48.3 μg/ml; p=0.004). When adjusted for SFR children with Down syndrome had mean sIgA levels of 98.8 μg/min and the siblings 48.6 μg/min (p=0.008). The children with Down syndrome had sIgA levels similar to those of the parents (92.5 μg/ml; 93.2 μg/min). There was a positive correlation between age and sIgA concentration in the siblings (p=0.008) but not for children with Down syndrome (p=0.363). This suggests that under similar environmental influences, the levels of sIgA in children with Down syndrome are higher than in the siblings, from a very young age.

Thymic-thoracic ratio in fetuses with trisomy 21, 18 or 13

OBJECTIVES

To assess thymic size expressed as the thymic-thoracic ratio (TT-ratio) in fetuses with trisomy 21, 18 or 13.

METHODS

The TT-ratio, the quotient of the anteroposterior thymic and the intrathoracic mediastinal diameter, was measured in 65 trisomic fetuses between 15 and 36 weeks' gestation, including 30 cases with trisomy 21, 19 with trisomy 18 and 16 with trisomy 13. In addition these 65 fetuses were divided into two groups, according to whether they showed growth that was appropriate-for-gestational age (AGA) (n = 39) or intrauterine growth restriction (IUGR) (n = 26). Measurements were compared with reference ranges from 302 normal fetuses.

RESULTS

The TT-ratio was low in 27.7% (n = 18) of the 65 fetuses with aneuploidy. In comparison to normal fetuses (mean TT-ratio, 0.44), those with trisomy 18 or 21 had a significantly smaller TT-ratio (mean, 0.38 (P < 0.001) and 0.40 (P < 0.05), respectively), while those with trisomy 13 did not (mean, 0.43). These values were not as low as those observed previously in fetuses with del.22q11, suggesting a mechanism involving accelerated thymic involution rather than primary thymic hypoplasia. Furthermore, the TT-ratio was significantly lower than normal in both AGA (P < 0.05) and IUGR (P < 0.001) fetuses.

CONCLUSION

Fetuses with trisomy 18 or 21, but not trisomy 13, have a small thymus, suggesting accelerated thymic involution in utero. IUGR may contribute to the reduced thymic size in trisomy 18 fetuses. Trisomy 21 fetuses seem to have additional factors leading to a small thymus which could be a possible confirmation of the reduced immune response observed in fetuses and neonates with Down syndrome.

Distinct abnormalities in the innate immune system of children with Down syndrome

OBJECTIVE

To analyze the frequency and phenotype of cells of the innate immune system in the peripheral blood of children with Down syndrome (DS).

STUDY DESIGN

Flow cytometric analysis of expression of cell surface markers was performed in children with DS (n = 41) and healthy age-matched controls (n = 41).

RESULTS

Compared with controls, children with DS had significantly lower absolute total leukocyte counts, lymphocytes, monocytes, and granulocytes, but 1.5-times higher absolute numbers of CD14(dim)CD16(+) monocytes (147 x 10(6)/L vs 93 x 10(6)/L; P = .02). This difference is fully explained by a higher percentage of CD14(dim)CD16(+) monocytes within the monocyte compartment (28.7% vs 13.4%; P <.001). The absolute numbers of myeloid dendritic cells were lower in DS (13.8 x 10(6)/L vs 22.7 x 10(6)/L; P <.001). The numbers of plasmacytoid dendritic cells and natural killer cells were normal. Absolute numbers of invariant natural killer T cells were very low overall, but significantly lower in children with DS than in controls (1.2 x 10(6)/L vs 3.7 x 10(6)/L; P = .01).

CONCLUSIONS

Children with DS exhibited distinct abnormalities in cells of the innate immune system. Most strikingly, they had a high number of proinflammatory CD14(dim)CD16(+) monocytes. This elevated level of CD14(dim)CD16(+) monocytes may play an important role in the onset and maintenance of chronic inflammatory disease in DS.

Maternal health conditions during pregnancy and acute leukemia in children with Down syndrome: A Children's Oncology Group study

BACKGROUND

Children with Down syndrome (DS) have about a 20-fold increased risk of developing leukemia. Early childhood infections may protect against acute lymphoid leukemia (ALL) in children with and without DS. We examined whether maternal infections and health conditions during pregnancy were associated with acute leukemia in children with DS.

PROCEDURE

We conducted a case-control study of 158 children with DS and leukemia (including 97 cases with acute lymphoblastic leukemia (ALL) and 61 cases with acute myeloid leukemia (AML)) and 173 children with DS during the period 1997-2002. Maternal interview included information about 14 maternal conditions during gestation that are likely to induce an inflammatory response. We evaluated their prevalence in cases and controls. Five of these were common enough to allow analyses by leukemia subtype.

RESULTS

Vaginal bleeding was the most frequent (18% cases, 25% controls) and was associated with a reduced risk (odds ratio (OR) = 0.57; 95% confidence interval (CI) = 0.33-0.99) for all cases combined. Other variables, while showing a potential trend toward reduced risk had effect estimates, which were imprecise and not statistically significant. In contrast, amniocentesis was marginally associated with an increased risk of AML (OR = 2.06, 95% CI = 0.90-4.69).

CONCLUSIONS

Data from this exploratory investigation suggest that some health conditions during pregnancy may be relevant in childhood leukemogenesis. Larger epidemiological studies and other model systems (animal, clinical studies) may provide a clearer picture of the potential association and mechanisms.

Intrinsic defect of the immune system in children with Down syndrome: a review

Down syndrome (DS) is the most frequent cause of mental retardation in man. Immunological changes in DS have been observed since the 1970s. The neurological system appears to be ageing precociously, with early occurrence of Alzheimer disease; until now, the observed immunological differences have been interpreted in the same context. Looking back at past and present results of immunological studies in DS children in relation to the clinical consequences they suffer, we conclude that it is more likely that the DS immune system is intrinsically deficient from the very beginning.

Phenotype of apoptotic lymphocytes in children with Down syndrome

Background

Down syndrome (DS) is the most common and best-known chromosomal disorder and is associated with several other pathologic conditions including immunodeficiency which makes a significant contribution to morbidity and mortality. Various immunological theories and observations to explain the predisposition of individuals with DS to various infections have been published, one of which is increased apoptotic cells.

Aim

The aim of this study was to identify the effect of apoptosis on both types of cells of specific immune response (T and B lymphocytes) in children with DS using Annexin V staining of phosphatidyserine (PS) as a specific marker of early apoptosis.

Subjects and methods

The study included 17 children with karyotypically ascertained DS (7 males and 10 females). Their ages ranged from 4 months to 14 years with mean age of 5.7 ± 4.35 years. Seventeen age and sex matched healthy children were included in the study as controls. Patients or controls with infections were excluded from the study. Complete blood picture, immunophenotyping, analysis of apoptosis using Annexin V was done at National cancer Institute to all children included in this study.

Results

Although CBC, differential count, relative and absolute number of CD³⁺ and CD¹⁶⁺ did not show significant differences between DS children and control group, the relative and the absolute size of apoptotic CD³⁺ T lymphocytes, and the relative size of apoptotic CD¹⁹⁺ B lymphocytes were significantly higher in DS children than in controls. On the other hand, no significant difference was detected as regards the absolute size of CD¹⁹⁺ B lymphocytes in DS children and in controls

Conclusion

our finding of increased early apoptotic cells (especially T cells) in DS children may emphasize the fact that the function of cells- and not their number- is main mechanism responsible for the impairment of the immune system in DS children and may further add to the known fact that cellular immunity is more severely affected than humoral immunity in these children. Further studies on apoptotic cellular phenotype in larger number of DS are needed

Genetic syndromic immunodeficiencies with antibody defects

This article reviews the major syndromic immunodeficiencies with significant antibody defects, many of which may require intravenous immunogammaglobulin therapy. The authors define syndromic immunodeficiency as an illness associated with a characteristic group of phenotypic abnormalities or laboratory features that comprise a recognizable syndrome. Many are familial with a defined inheritance pattern. Immunodeficiency may not be a major part of the illness and may not be present in all patients; thus, these conditions differ from primary immunodeficiency syndromes, in which immune abnormalities are a consistent and prominent feature of their disease.

Immunological patterns in young children with Down syndrome: is there a temporal trend?

Down syndrome is associated with an increased susceptibility to infections due to a deficiency of both specific and nonspecific immunity.

AIM

The aim of the study was to analyze the temporal trends, if any, of some variables related to the immunological status of children affected by Down syndrome.

METHODS

Heparinized blood samples were obtained by venipuncture in 30 children with Down syndrome, who were regularly followed in our department and analyzed for hematologic values, lymphocyte subpopulations, immunoglobulin dosage and zinc level. Results were compared with those of the normal population.

RESULTS

In the first 5 years of life, we observed a progressive decrease in the medium values of lymphocytes, CD4(+) and plasma zinc levels, and an increase in CD8(+), immunoglobulin A, immunoglobulin G, immunoglobulin M and natural killer, but generally without exceeding the interval of normality.

CONCLUSIONS

In Down syndrome children, the immune cellular status is similar to the normal population as far as white blood cell, lymphocyte, CD4(+), CD8(+), natural killer and immunoglobulins are concerned. Plasma level of zinc is normal from birth until 5 years but with a temporal trend of progressive reduction. This observation supports the hypothesis that a pharmacological supplementation may be necessary in Down syndrome children only after 5 years of age.

Age-dependent deficiency in saliva and salivary antibodies secretion in Down's syndrome

OBJECTIVE

Down's syndrome (DS) individuals suffer from an increased susceptibility to infections. Here, we assessed age-related changes in the salivary-specific humoral immunity of DS subjects.

DESIGN

Parotid and whole saliva were collected from a young group of DS (YDS, n=30, 23.3+/-4 years), an older group of DS individuals (ODS, n=10, 51.9+/-8 years) and compared to two age-matched groups of healthy volunteers--a young group (YC, n=29, 22.8+/-5 years) and an older group (OC, n=10, 48.4+/-9 years). The levels of total IgA, and specific antibodies to three common oral pathogens (Porphyromonas gingivalis, Actinobacillus (Aggregatibacter) actinomycetemcomitans and Streptococcus mutans) were analysed.

RESULTS

The limited increases in IgA concentrations could not compensate the dramatic reduction in the salivary flow rate observed in DS individuals. Therefore, the median secretion rates of the specific antibodies in whole and parotid saliva were 70-77% and 34-60% (respectively) lower in YDS individuals as compared to YC and farther 77-100% and 75-88% (respectively) lower in ODS compared to YDS. In contrast, the antibody secretion rates were similar for parotid saliva, or even increased for whole saliva of OC, compared with YC. Consequently, a dramatic cumulative extreme reduction (>92%) in the bacterial specific salivary antibodies differentiated the adult DS individuals from to their age-matched controls.

CONCLUSIONS

Our results indicate a severe immunodeficiency in the secretion rate of the specific salivary IgA response of in DS individuals which intensifies with age.

Evaluation of the relationship between caries indices and salivary secretory IgA, salivary pH, buffering capacity and flow rate in children with Down's syndrome

The aim of this study was to compare the caries prevalence and salivary secretory IgA (sIgA), salivary pH, buffering capacity and flow rate between Down's syndrome (DS) and control subjects. Seventy-three institutionalised children with DS and 70 normal children aged 7-12 years old were included in this study. Tooth-brushing habits and daily dietary sugar exposures of the children, family income and education levels of the parents were recorded. DMFS and dfs scores were assessed according to the World Health Organisation's criteria and stimulated whole saliva samples were collected. Salivary sIgA levels were determined by radial immunodiffusion technique, the average salivary flow rate was measured from the total volume, and salivary pH and buffering capacity were determined using a pH micro-electrode. All data were analysed using SPSS version 11.0. The DMFS and dfs scores were significantly lower in the DS group than the control group (P < 0.05). Otherwise, the difference in plaque scores between the DS and control groups was not statistically significant (P > 0.05). There were no significant differences in tooth-brushing habits and daily dietary sugar exposures of the children, family income and education levels of the parents between the two groups (P > 0.05). Salivary sIgA levels were significantly higher in the DS group (P < 0.05). Salivary pH, buffering capacity and flow rate were quite similar in both the DS and control groups (P > 0.05). In conclusion, the patients with DS had a significantly lower prevalence of caries and significantly higher levels of salivary sIgA in this study. This finding tends to support the hypothesis that higher levels of salivary sIgA may protect against dental caries.

Risk of death for children with down syndrome and sepsis

OBJECTIVE

To determine differences in case fatality rates between children with and without Down syndrome.

STUDY DESIGN

We used the Pediatric Health Information System (PHIS) database, which includes demographic and diagnostic data from freestanding children's hospitals. Using Poisson regression, we determined the risk of mortality from sepsis for children with Down syndrome, after controlling for potential confounding factors.

RESULTS

A total of 35,645 patients met our inclusion criteria, of which 3936 (11%) died during hospitalization. Altogether, 620 of the included patients also had a diagnosis of Down syndrome; 106 (17%) of these died during hospitalization. Children with Down syndrome had significantly elevated risk of mortality (mortality rate ratio = 1.30; 95% confidence interval = 1.06 to 1.59) after adjusting for potential confounding factors including demographics, pathogens, and concomitant conditions.

CONCLUSIONS

Children with Down syndrome and sepsis have elevated risk of mortality. These findings have implications for treatment decisions, communications about prognosis, and future research.

Growth delay in Down syndrome and zinc sulphate supplementation

Children affected with Down syndrome (DS) show deficient growth, immunodeficiency--especially concerning the T-cell population--and low plasma zinc levels. New growth charts have been recently proposed, and zinc supplementation to the diet has been reported to improve transiently the efficiency of the immune system. The aim of this study was to evaluate if in DS children zinc sulphate therapy could improve the growth rate and affect some endocrine parameters. We studied 22 patients (16 males and 6 females) who received zinc sulphate for 6 to 9 months. Fifteen of 22 patients studied reached a higher centile in their growth rate, whereas the remaining seven showed no change, at least to date. The average height velocity changed from 23.84 +/- 7.98 mm/6 months to 40.80 +/- 7.68 mm/6 months. Growth hormone serum level was 5.94 +/- 4.89 ng/ml compared with 7.49 +/- 6.75 ng/ml before and after therapy, respectively. Somatomedin serum level was 160.27 +/- 68.88 mU/ml and 205 +/- 124.07 mU/ml before and after therapy, respectively. In conclusion, zinc sulphate therapy of patients with DS affects not only the immune system, as previously reported, but can also accelerate growth.

Precocious aging of the immune system in Down syndrome: alteration of B lymphocytes, T-lymphocyte subsets, and cells with natural killer markers

Phenotype and proliferative ability of peripheral blood lymphocytes from 15 noninstitutionalized children affected with Down Syndrome (DS), in apparently good health, were studied and compared with those of 16 healthy control children of the same age. A complex derangement of all the major peripheral blood cell subsets, i.e., B cells, T cells, and natural killer (NK) cells, was present in DS children. A significant decrease of the absolute number of circulating lymphocytes, a marked and significant decrease of B lymphocyte absolute number and percentage, and dramatic modifications of the T-cell subsets were observed. The absolute number of CD4+ cells was significantly decreased, whereas CD8+ cells increased significantly in percentage but not in absolute number. A derangement of cells bearing markers associated with NK activity, such as CD57, CD16, and CD56, was observed. Among the most important alterations, the presence of a high number of CD57+, CD16- cells, of CD57+, CD8+ lymphocytes, and of CD3+, CD56+ lymphocytes was seen. Many of these alterations are similar to those characteristic of chromosomally normal subjects of advanced age. The hypothesis that the reduced thymic endocrine activity and the zinc deficiency characteristic of DS are responsible for the derangement of T and NK subsets is discussed.

Epidemiology of leukemia in children with Down syndrome

Studies suggest nearly a 20-fold increased risk of leukemia in individuals with Down syndrome. Most of this increased risk appears in the first few decades of life, with the highest incidence in children less than 5 years of age. It is unknown why children with Down syndrome are at such an increased risk of leukemia. With respect to environmental exposures, it will be important to investigate risk factors associated with childhood leukemia in general (including diagnostic x-rays, pesticides, and other occupational exposures) as well as experiences common to children with Down syndrome (including routine medical screening tests, increased susceptibility to infections, and increased vitamin deficiencies).

Immunogenicity and safety of an inactivated hepatitis A vaccine in children with Down syndrome

OBJECTIVES

Hepatitis A vaccine has not been investigated in children with Down syndrome. The aim of this study was to evaluate immunogenicity and safety of an inactivated hepatitis A vaccine in noninstitutionalized children with Down syndrome and compare their responses to those of healthy control children.

METHODS

An open, prospective, controlled trial of 127 children ages 1 to 12 years, 63 with Down syndrome and 64 healthy control subjects, was conducted at a single hospital. Inactivated hepatitis A virus (HAV) vaccine containing 720 enzyme-linked immunosorbent assay units of alum-adsorbed HAV was administered intramuscularly in a two-dose schedule at 0 and 6 months. Seroconversion and anti-HAV titers were measured at months 1 and 7.

RESULTS

Seroconversion rates at month 1 were 92% and 94% and geometric mean titers (GMT) were 164.02 and 160.77 mIU/mL in the Down syndrome (DS) and control groups, respectively. At month 7, seroconversion rates were 100% in both groups, with GMT of 1,719.86 and 2,344.90 mIU/mL in the DS and control groups, respectively (P = 0.117). Both doses were well tolerated and no significant adverse events observed. Local reaction at the injection site was the most common adverse event reported in both groups (15% in DS and 11% in controls).

CONCLUSIONS

The authors' data demonstrate a good response to HAV vaccination in children with DS living at home, with GMT not statistically different from that of healthy control children. HAV vaccine is well tolerated and highly immunogenic in children with DS.

Syndromic immunodeficiencies: genetic syndromes associated with immune abnormalities

In syndromic immunodeficiencies, clinical features not directly associated with the immune defect are prominent. Patients may present with either infectious complications or extra-immune medical issues. In addition to the immunologic abnormality, a wide range of organ systems may be affected. Patients may present with disturbances in skeletal, neurologic, dermatologic, or gastrointestinal function or development. These conditions can be caused by developmental abnormalities, chromosomal aberrations, metabolic disorders, or teratogens. For a number of these conditions, recent advances have resulted in an enhanced understanding of their genetic basis. The finding of immune deficits in a number of defined syndromes with congenital anomalies suggests that an underlying genetic syndrome should be considered in those patients in whom a significant non-immune feature is present.

Pediatric pacemaker infections: twenty years of experience

OBJECTIVE

We sought to evaluate possible predictors of early and late pacemaker infections in children.

METHODS

A review was performed of all pacemakers implanted in children at The Children's Hospital of Philadelphia between 1982 and 2001. Infections were classified as superficial cellulitus, deep pacemaker pocket infection necessitating removal, or positive blood culture without an identifiable source.

RESULTS

A total of 385 pacemakers (224 epicardial and 161 endocardial) were implanted in 267 patients at 8.4 +/- 6.2 years. All 2141 outpatient visits were reviewed (median follow-up, 29.4 months; range, 2-232 months). There were 30 (7.8%) pacemaker infections: 19 (4.9%) superficial infections; 9 (2.3%) pocket infections; and 2 (0.5%) isolated positive blood cultures. All superficial infections resolved with intravenous antibiotics. The median time from implantation to infection was 16 days (range, 2 days-5 years). Only 1 deep infection occurred after primary pacemaker implantation. Six patients with deep infections were pacemaker dependent and were successfully managed with intravenous antibiotics, followed by lead-generator removal and implantation of a new pacemaker in a remote location. In univariate analyses trisomy 21 (relative risk, 3.9; P <.01), pacemaker revisions (relative risk, 2.5; P <.01), and single-chamber devices (relative risk, 2.4; P <.05) were identified as predictors of infection. However, in multivariate analyses only trisomy 21 and pacemaker revisions were predictors.

CONCLUSIONS

The incidences of superficial and deep pacemaker infections were 4.9% and 2.3%, respectively. Trisomy 21 and pacemaker revisions were significant risk factors in the development of infection after pacemaker implantation. For primary pacemaker implantation, the risk of infection requiring system removal is low (0.3%).

Severe impairment of secretory Ig production in parotid saliva of Down Syndrome individuals

Infections associated with Down Syndrome (DS) are prevalent in the mucosal-gastrointestinal and respiratory systems, for reasons that are uncertain. The purpose of the present study was to assess the levels of parotid salivary immunoglobulins (Ig) in a group of DS individuals as a possible factor in the susceptibility of mucosal surfaces to infections. Twenty-nine DS and 10 age- and sex-matched healthy individuals were included. Salivary flow rate and IgA, IgG, and IgM concentrations were recorded. The secretion rates of IgA and IgG were diminished by 83% (p < 0.001) and 75% (p = 0.05), respectively, whereas the secretion rate of IgM was not statistically significantly lower. Analysis of the data suggests that DS individuals are immunodeficient in the humoral mucosal immune response. This may explain, in part, the high incidence of recurrent infections in target organs of the secretory immune system in DS subjects.

Lack of age-associated LFA-1 up-regulation and impaired ICAM-1 binding in lymphocytes from patients with Down syndrome

To investigate the role of LFA-1 in the immune defects in DS patients, we analysed lymphocytes from DS patients in LFA-1 expression and LFA-1 mediated cell adhesion. DS patients less than 2 years of age expressed a higher level of LFA-1 when compared with age-matched controls. The difference in LFA-1 expression was much less significant in older DS patients when compared with age-matched children. Although older children (2-15-year-old groups) without DS tend to increase their expression of lymphocyte LFA-1 when compared with younger normal children (0-2 years old), DS patients showed no age-associated increase in lymphocyte LFA-1 expression. Two-colour analysis with CD4/CD8 and LFA-1 in patients and controls showed that proportions of CD4 + lymphocytes were comparable in DS patients and controls, while the proportion of CD8 + lymphocytes was higher in older DS patients. Expression levels of LFA-1 on both CD4 + and CD8 + lymphocytes in younger DS patients were higher when compared with age-matched controls and close to the expression levels in the older DS group. Proportions of memory lymphocytes expressing the CD45RO isoform were higher in both younger and older DS patients when compared with age-matched control groups. Noticeably, the LFA-1 expression levels on CD45RO lymphocytes from younger DS patients were higher than the levels of the controls and declined in the older DS group. We tested lymphocytes (EBV transformed B cells, resting and anti-CD3 stimulated T cells) for cellular adhesion to recombinant ICAM-1 and found that lymphocytes from DS patients were less adhesive, even though their beta2 integrin expression was comparable with that of normal controls. These results suggest that more generalized pathological processes, such as early senescence of the immune system or ineffective lymphocyte activation, and subsequent integrin dysfunction may underlie the immune defects in DS patients.

Allogeneic marrow grafts from donors with congenital chromosomal abnormalities in marrow cells

To determine whether siblings with chromosomal abnormalities in marrow cells which are associated with cellular defects (e.g. Down syndrome or heterozygosity for Fanconi syndrome) are suitable donors for allogeneic bone marrow transplants, we have reviewed the patient files at the Fred Hutchinson Cancer Research Center (FHCRC) and carried out a survey among member centres of the International Bone Marrow Transplant Registry (IBMTR). The 57 of 253 (23%) member centres which responded to the survey reported seven transplants from donors with the following conditions: Down syndrome (n = 2), suspected heterozygotes for Fanconi syndrome (n = 3), and 47,XXX syndrome (n = 2), among a total of 5,561 allogeneic transplants from HLA-identical siblings. Adding the three cases seen at the Fed Hutchinson Cancer Research Center among 2,927 HLA-identical sibling transplants during 1992 resulted in 10 transplants among 8,488 cases transplanted overall: four with Down syndrome, four suspected of being heterozygous for Fanconi syndrome, and two trisomy X. Three out of four grafts from siblings with Down syndrome had complications, including poor graft function (n = 2) and graft failure (n = 1). Two of four recipients of marrow from presumed Fanconi syndrome heterozygotes presented with poor graft function and a third recipient developed graft failure after initial evidence of engraftment. The two patients given marrow from siblings with 47,XXX syndrome engrafted uneventfully. The experience reported here shows a low frequency of encountering an HLA-identical sibling donor who has chromosomal abnormalities in marrow cells consistent with Down syndrome or heterozygosity for Fanconi syndrome, about one case among 1,000 transplants. The much higher than expected incidence of graft problems with marrow from such a donor would make it reasonable to look either for an alternative marrow donor or consider an autologous transplant, in case a sibling marrow donor with Down syndrome or heterozygosity for Fanconi syndrome is encountered, although a donor with trisomy X seems acceptable.

Down syndrome associated with systemic lupus erythematosus: a mere coincidence or a significant association?

An 8-year-old male, who had Down syndrome associated with systemic lupus erythematosus (SLE), is described. He also had a partial complement 4 deficiency. This case is a reminder that the physician should be aware of the possibility of an immune defect in a male presenting with SLE at a young age. The question of whether the association of Down syndrome with SLE is coincidental or whether there is a predilection for autoimmune disorders in Down syndrome is discussed.

Oral zinc supplementation in Down's syndrome subjects decreased infections and normalized some humoral and cellular immune parameters

The effect of 4 months of oral zinc supplementation on immune functions in non-institutionalized young female and male Down's syndrome (DS) subjects was studied. Along with plasma levels of zinc, the immune parameters, measured before and after zinc treatment, were plasma levels of thymulin, the percentage and the absolute number of circulating white blood cells, total lymphocytes, lymphocyte subpopulations, the mitogen-induced lymphocyte proliferation, the production of interleukin-2, and the activity of stimulated granulocytes. Some immune parameters were significantly influenced by zinc treatment. In particular, a normalization of thymulin and zinc plasma levels were found in these subjects after zinc supplementation. At the end of the clinical trial, in vitro lymphocyte proliferation and polymorphonuclear activity also increased and reached normal values. Zinc administration exerted a positive clinical effect in these children, since a reduced incidence of infections was found.

Abnormal fetal immunological development in Down's syndrome

OBJECTIVE

To investigate the intrauterine development of the immune system in Down's syndrome.

DESIGN

Cross sectional study.

SETTING

Harris Birthright Research Centre for Fetal Medicine, London, UK.

SUBJECTS

16 fetuses with Down's syndrome and 104 fetuses with a normal karyotype at 17-24 weeks gestation.

MAIN OUTCOME MEASURE

Flow cytometry was used to enumerate T (CD3+), B (CD19+) and NK (CD3- & CD16+/CD56+) lymphocyte subpopulations in fetal blood obtained by cordocentesis.

RESULTS

The median numbers of T, B and NK lymphocytes in fetuses with Down's syndrome (1.52 x 10(9)/l, 0.08 x 10(9)/l, and 0.10 x 10(9)/l, respectively) were significantly lower than in the chromosomally normal fetuses (T lymphocytes: 1.98 x 10(9)/l, z = 3.04, P < 0.01; B lymphocytes: 0.50 x 10(9)/l, z = 5.84, P < 0.0001; and NK lymphocytes: 0.19 x 10(9)/l, z = 3.14, P < 0.01).

CONCLUSION

These data demonstrate that in Down's syndrome, there is abnormal intra-uterine development of the immune system.

Non-efficacy of low-dose intradermal vaccination against hepatitis B in Down's syndrome

Persons with Down's syndrome (DS) constitute a risk group for hepatitis B (HB) and are recommended to be immunized. Of 123 persons with DS in Orebro county screened for markers of HB, 31% had such markers; 16% were potentially contagious. 83 persons without markers participated in a comparative trial of the immunogenicity of a recombinant HB vaccine given either intramuscularly (IM) or in a lower dose intradermally (ID). Immunity developed in 73% after IM vaccination as compared to 29% of those given ID vaccination (p < 0.005). At 3-year follow-up half and two-thirds of the immune persons, respectively, had lost their immunity. Those > 30 years had a poor immunization response compared to the younger ones (p < 0.01). Only 19% of the non-responders developed immunity after an IM booster dose given 10 months after the third injection. Intradermal vaccination is not warranted in persons with DS, especially not in middle aged and older persons. A booster dose of vaccine does not ascertain immunity in those who do not respond with immunity to the ordinary immunization schedule. Post-vaccination immunity should therefore be controlled.

Zinc affects the metabolism of thyroid hormones in children with Down's syndrome: normalization of thyroid stimulating hormone and of reversal triiodothyronine plasmic levels by dietary zinc supplementation

Levels of circulating thyroid stimulating hormone (TSH), tetraiodothyronine (T4), 3,5,3'-triiodothyronine (T3), and 3,3',5' triiodothyronine (reversal T3 or rT3) were measured in 25 children with trisomy of chromosome 21, also known as Down's syndrome (DS), and in 14 normal children. In subjects with DS TSH levels were increased, while plasmic levels of rT3 were decreased. No alteration in T3 and T4 levels was observed. Before zinc supplementation, plasmic levels of zinc and thymulin, a zinc dependent thymic hormone, were significantly decreased in DS children. After four months of dietary supplementation with zinc sulphate, a normalization of plasmic zinc, thymulin and TSH levels was observed. Plasmic levels of rT3 significantly increased, and after zinc treatment no difference was detectable between DS children and normal children. Clinical evaluation of the health status of DS children showed that zinc supplementation decreased the incidence of infectious diseases and improved school attendance. Thus, the increased efficiency of the immune system and the normalization of some endocrine parameters by zinc supplementation suggests that zinc deficiency may play a crucial role in some of the pathological manifestations associated with the syndrome, such as infections and malfunctioning of the thyroid gland.

Upregulation of lymphocyte beta-adrenergic receptor in Down's syndrome: a biological marker of a neuroimmune deficit

To test the hypothesis of an altered central nervous system influence upon the immune system of Down's syndrome (DS) patients and in order to establish a peripheral biological marker of neuroimmune deficit, we have studied the characteristics of the beta 2-adrenergic receptor (B2AR) system in peripheral blood monocytes (PBMC) of 12 pre-pubertal (six boys and six girls) individuals and correlated alterations in binding with changes in distribution of lymphocyte subsets. Using the very potent beta-adrenergic antagonist, iodocyanopindolol ([125I]CYP), as a ligand, the present study shows that a typical BAR population of the beta 2-subtype is present in PBMC from DS children, with binding kinetics and structural specificity similar to those measured in PBMC from patients with other (non-genetic) forms of mental retardation, or in PBMC from age-matched healthy subjects. On the other hand, this study revealed a significant increase in B2AR binding capacity of PBMC from DS subjects (Bmax = 5258 +/- 470 sites/cell) compared to the values measured in the control population of retarded children (Bmax = 1965 +/- 280 sites/cell), characterized by an approximately three-fold increase in the Bmax, without changes in binding affinity (KD = 40.5 +/- 2.0 and 36.6 +/- 2.5 pM in DS and retarded patients, respectively). The flowcytometric analysis of lymphocyte subsets using a panel of monoclonal antibodies against a series of lymphocyte markers revealed a profound alteration in the distribution of lymphocyte subtypes with an almost 50% decrease in B cell and T-helper populations, a three-fold increase in T-cytotoxic suppressor, a seven-fold increase in lymphocyte-activated killer cells (LAK) and 30% increase in natural killer (NK) subpopulations. When fluorescence-labelled lymphocytes were visualized in the cytofluorograph and sorted for their use in the radioreceptor assay, B cells had approximately twice the number of B2AR when compared to T cells; and cytotoxic/suppressor showed a higher binding capacity compared to T-helper cells. On the other hand, labelled lymphocytes from DS patients showed a specific increase in receptor number in B cells, T-cytotoxic suppressor and NK subpopulations. It is concluded that a profound catecholaminergic dysfunction not previously appreciated in DS is reflected by a significant alteration in lymphocyte subset distribution and by a specific up-regulation of lymphocyte B2AR in phenotypically and functionally distinct T and B cells as well NK subpopulations, suggesting a possible denervation supersensitivity phenomenon.(ABSTRACT TRUNCATED AT 400 WORDS)

Down syndrome (DS) peripheral blood contains phenotypically mature CD3+TCR alpha, beta+ cells but abnormal proportions of TCR alpha, beta+, TCR gamma, delta+, and CD4+ CD45RA+ cells: evidence for an inefficient release of mature T cells by the DS thymus

Down syndrome (DS) thymocytes have a markedly diminished proportion of cells expressing high levels of the alpha, beta T cell receptor (TCR alpha, beta) and the associated CD3 molecule. Thus, we examined the surface expression of TCR alpha, beta and CD3 as well as TCR gamma, delta, CD4, CD8, CD16, and CD45RA on peripheral blood lymphocytes (PBL) from 13 noninstitutionalized subjects with DS and 13 closely age-matched sibling controls using immunofluorescence and flow cytometry. DS PBL expressed high surface levels of TCR alpha, beta and CD3, but, as compared to controls, they had a lower proportion of cells expressing TCR alpha, beta (61% vs. 68%, respectively; P less than or equal to 0.05). Moreover, the absolute number of TCR alpha, beta+ cells was considerably lower for DS subjects than for controls (1634 +/- 229 vs. 2763 +/- 530, respectively; P less than or equal to 0.05). DS subjects had a markedly higher proportion of cells expressing TCR gamma, delta than did the controls (12% vs. 7%, respectively; P less than or equal to 0.02). In addition, DS subjects had a lower proportion of CD4+CD45RA+ cells than controls (22% vs. 35%, respectively; P less than or equal to 0.02), representing naive T cells which have recently emigrated from the thymus. The imbalance in the proportions of T cell subpopulations we have observed in DS PBL may contribute to the increased susceptibility to infection associated with DS and may represent a diminished efficiency in the production of newly differentiated T cells by the DS thymus.

Immunodeficiency and plasma zinc levels in children with Down's syndrome: a long-term follow-up of oral zinc supplementation

To evaluate the possible effect of zinc treatment on immune disorders in children with Down's syndrome (DS), 38 noninstitutionalized DS children were investigated. Twenty-four patients (63.2%) had plasmatic zinc levels lower than 0.70 microgram/dl ("hypozinkemic," LZn) and 14 patients (36.8%) had levels higher than 0.75 microgram/dl ("normozinkemic," NZn). No correlation was found between the zinc deficiency and recurrence and/or intensity of infections. The absolute numbers of peripheral lymphocytes, the percentages of B lymphocytes, total T cells, and serum IgG, IgA, and IgM levels did not differ between the DS children and the controls. Eight (21%) patients had CD4+ T cell counts below the lowest value for the controls. Seventeen (44%) DS patients had increased levels of CD8+ T cells. The mean percentage of Leu 7+ cells in DS subjects (22.8 +/- 12.9%) was significantly higher than that in controls (15.8 +/- 4.8%) (P less than 0.01). Notably, Ig levels and numbers of lymphocytes in each subset did not show any significant difference in NZn and LZn trisomic subjects. On the contrary the peripheral blood mononuclear cells (PBMCs) from LZn DS children showed a significantly lower proliferative response to phytohemagglutinin (PHA) (S.I. = 23.4 +/- 22.4) than that of PBMCs from NZn DS children (S.I. = 46.1 +/- 21.5, P less than 0.01). A significant increase in DNA synthesis was obtained after oral administration of zinc sulfate (20 mg/kg/day, for 2 months). The lymphocyte response to PHA appeared to be normal in all patients up to 6 months after the end of the zinc treatment and it became low in half of the patients 22 months after therapy.

Prognosis of Down's syndrome with acute leukaemia

The outcome in children with acute leukaemia with (n = 90) and without Down's syndrome (n = 4377) was compared. Sixty three (70%) of those with Down's syndrome had acute lymphoblastic leukaemia and in comparison with 3664 (84%) controls had similar prognostic features except for a significant excess of the 'common' immunological subtype of acute lymphoblastic leukaemia. The outcome of the children with Down's syndrome was significantly worse with a five year overall actuarial survival of 28% compared with 59% in the control group. It appeared that both suboptimal chemotherapy and a high rate of infective problems contributed to the poor survival. Twenty six children with Down's syndrome had acute myeloblastic leukaemia and were significantly younger and had a higher percentage of the megakaryocytic and erythroid subtypes of acute myeloblastic leukaemia than the 713 controls. The outcome was similar in the two groups. It is concluded that the patients with Down's syndrome who develop acute leukaemia should receive standard protocols without modification, but aggressive supportive care is necessary to improve outcome.

Infection and immunity in Down syndrome: a trial of long-term low oral doses of zinc

To determine whether orally administered zinc supplements could correct the abnormal humoral and cell-mediated immunity of Down syndrome, we randomly assigned 64 children with Down syndrome, aged 1 to 19 years and living at home, to receive either zinc gluconate or placebo daily for 6-month periods with crossover from one regimen to another. Control subjects were siblings and age-matched, unrelated children. Serum zinc, copper, and measures of immune system competence were tested at 3- or 6-month intervals. Parents kept daily logs of clinical symptoms such as cough and diarrhea and of physician visits. Mean serum zinc concentrations increased to about 150% of baseline during zinc supplementation, but we found no effect on serum levels of copper, immunoglobulins, or complement; on lymphocyte number or subset distribution; or on in vitro response to mitogens. Children with Down syndrome who were receiving zinc had a trend toward fewer days or episodes of cough and fever but no change in other clinical variables. Long-term, low-dose oral zinc supplementation to improve depressed immune response or to decrease infections in children with Down syndrome cannot be recommended.