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

Zinc metabolism and its role in immunity status in subjects with trisomy 21: chromosomal dosage effect

Introduction

Trisomy 21 (T21), which causes Down syndrome (DS), is the most common chromosomal aneuploidy in humankind and includes different clinical comorbidities, among which the alteration of the immune system has a heavy impact on patient's lives. A molecule with an important role in immune response is zinc and it is known that its concentration is significantly lower in children with T21. Different hypotheses were made about this metabolic alteration and one of the reasons might be the overexpression of superoxide dismutase 1 (SOD1) gene, as zinc is part of the SOD1 active enzymatic center.

Methods

The aim of our work is to explore if there is a linear correlation between zinc level and immune cell levels measured in a total of 217 blood samples from subjects with T21. Furthermore, transcriptome map analyses were performed using Transcriptome Mapper (TRAM) software to investigate whether a difference in gene expression is detectable between subjects with T21 and euploid control group in tissues and cells involved in the immune response such as lymphoblastoid cells, thymus and white blood cells.

Results

Our results have confirmed the literature data stating that the blood zinc level in subjects with T21 is lower compared to the general population; in addition, we report that the T21/control zinc concentration ratio is 2:3, consistent with a chromosomal dosage effect due to the presence of three copies of chromosome 21. The transcriptome map analyses showed an alteration of some gene's expression which might explain low levels of zinc in the blood.

Discussion

Our data suggest that zinc level is not associated with the levels of immunity cells or proteins analyzed themselves and rather the main role of this ion might be played in altering immune cell function.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Clinical implications of immune-mediated diseases in children with Down syndrome

Children with Down syndrome have changes in their innate and adaptive immunity, which contribute to increased rates of infections, autoimmune diseases, and haematological malignancies. While improved care for congenital heart disease has decreased mortality and morbidity, complications related to immune-mediated diseases continue to limit the life expectancy in Down syndrome. Infectious diseases are common and have a significant effect on development, behaviour and quality of life. Infection frequency and severity are influenced by various anatomical and physiological alterations in addition to immunological changes in Down syndrome. Thus, prevention of respiratory tract infections requires a multifactorial approach. This could include additional active and/or passive immunizations, prophylactic antibiotics, immunoglobulin replacement and ear, nose and throat surgical interventions. Autoimmune conditions like coeliac disease, type I diabetes mellitus and thyroid disease are classically mentioned in the context of Down syndrome. However, autoinflammatory conditions are more prevalent as well. Screening for autoimmune diseases is required and immunosuppression has to be used with caution. Future studies should address optimal screening programmes for immune-mediated diseases in individuals with Down syndrome, as well as the effect of immune modulation, to further decrease morbidity and mortality, and improve the quality of life of individuals with Down syndrome.

Limited Evidence on the Management of Respiratory Tract Infections in Down's Syndrome: A Systematic Review

AIMS

To systematically review the effectiveness of preventative and therapeutic interventions for respiratory tract infections (RTIs) in people with Down's syndrome.

METHODS

Databases were searched for any published and ongoing studies of respiratory tract diseases in children and adults with Down's syndrome. These databases were searched for controlled trials, cohort studies and controlled before-after studies. Trial registries were searched for ongoing studies. Initially, all study types were included to provide a broad overview of the existing evidence base. However, those with a critical risk of bias were excluded using the Cochrane Risk of Bias tool.

RESULTS

A total of 13,575 records were identified from which 5 studies fulfilled the eligibility criteria and 3 fulfilled our criteria for data extraction. One randomized controlled trial of moderate risk of bias compared zinc therapy with placebo. Outcome data were only reported for 50 (78%) children who presented with extreme symptoms; no benefit of zinc therapy was found. One non-randomized controlled trial with serious risk of bias included 26 children and compared pidotimod (an immunostimulant) with no treatment; pidotimod was associated with fewer upper RTI recurrences compared with no treatment (1.43 vs. 3.82). A prospective cohort study with moderate risk of bias compared 532 palivizumab treated children with 233 untreated children and found that children treated with palivizumab had fewer respiratory syncytial virus-related hospitalization (23 untreated and 8 treated), but the same number of overall RTI-related hospitalizations (73 untreated and 74 treated) in the first 2 years of life.

CONCLUSIONS

The evidence base for the management of RTIs in people with Down's syndrome is incomplete; current studies included children only and carry a moderate to serious risk of bias. Methodologic rigorous studies are warranted to guide clinicians in how best to prevent and treat RTIs in children with Down's syndrome.

Zinc supplements for preventing otitis media

BACKGROUND

Otitis media is inflammation of the middle ear and is usually caused by infection. It affects people of all ages but is particularly common in young children. Around 164 million people worldwide have long-term hearing loss caused by this condition, 90% of them in low-income countries. As zinc supplements prevent pneumonia in disadvantaged children, we wanted to investigate whether zinc supplements could also prevent otitis media.

OBJECTIVES

To evaluate whether zinc supplements prevent otitis media in adults and children of different ages.

SEARCH METHODS

We searched CENTRAL (2014, Issue 1), MEDLINE (1950 to February week 4, 2014) and EMBASE (1974 to March 2014).

SELECTION CRITERIA

Randomised, placebo-controlled trials of zinc supplements given at least once a week for at least a month for preventing otitis media.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and methodological quality of the included trials and extracted and analysed data. We summarised results using risk ratios (RRs) or rate ratios for dichotomous data and mean differences (MDs) for continuous data. We combined trial results where appropriate.

MAIN RESULTS

No new trials were identified for inclusion in this update. We identified 12 trials for inclusion, 10 of which contributed outcomes data. There were a total of 6820 participants. In trials of healthy children living in low-income communities, two trials did not demonstrate a significant difference between the zinc-supplemented and placebo groups in the numbers of participants experiencing an episode of definite otitis media during follow-up (3191 participants); another trial showed a significantly lower incidence rate of otitis media in the zinc group (rate ratio 0.69, 95% confidence interval (CI) 0.61 to 0.79, n = 1621). A small trial of 39 infants undergoing treatment for severe malnutrition suggested a benefit of zinc for the mean number of episodes of otitis media (mean difference (MD) -1.12 episodes, 95% CI -2.21 to -0.03). Zinc supplements did not seem to cause any serious adverse events but a small minority of children were reported to have vomited shortly after ingestion of the supplements. The trial evidence included is generally of good quality, with a low risk of bias.

AUTHORS' CONCLUSIONS

Evidence on whether zinc supplementation can reduce the incidence of otitis media in healthy children under the age of five years living in low- and middle-income countries is mixed. There is some evidence of benefit in children being treated for marasmus (severe malnutrition), but this is based on one small trial and should therefore be treated with caution.

Oxidative stress and Down syndrome. Do antioxidants play a role in therapy?

Oxidative stress is a phenomenon associated with imbalance between production of free radicals and reactive metabolites (e.g. superoxide and hydrogen peroxide) and the antioxidant defences. Oxidative stress in individuals with Down syndrome (DS) has been associated with trisomy of the 21st chromosome resulting in DS phenotype as well as with various morphological abnormalities, immune disorders, intellectual disability, premature aging and other biochemical abnormalities. Trisomy 21 in patients with DS results in increased activity of an important antioxidant enzyme Cu/Zn superoxide dismutase (SOD) which gene is located on the 21st chromosome along with other proteins such as transcription factor Ets-2, stress inducing factors (DSCR1) and precursor of beta-amyloid protein responsible for the formation of amyloid plaques in Alzheimer disease. Mentioned proteins are involved in the management of mitochondrial function, thereby promoting mitochondrial theory of aging also in people with DS. In defence against toxic effects of free radicals and their metabolites organism has built antioxidant defence systems. Their lack and reduced function increases oxidative stress resulting in disruption of the structure of important biomolecules, such as proteins, lipids and nucleic acids. This leads to their dysfunctions affecting pathophysiology of organs and the whole organism. This paper examines the impact of antioxidant interventions as well as positive effect of physical exercise on cognitive and learning disabilities of individuals with DS. Potential therapeutic targets on the molecular level (oxidative stress markers, gene for DYRK1A, neutrophic factor BDNF) after intervention of natural polyphenols are also discussed.

Zinc supplements for preventing otitis media

BACKGROUND

Otitis media (OM) is inflammation of the middle ear and is usually caused by infection. It affects people of all ages but is particularly common in young children. Around 164 million people worldwide have long-term hearing loss caused by this condition, 90% of them in low-income countries. As zinc supplements prevent pneumonia in disadvantaged children, we wanted to investigate whether zinc supplements could also prevent OM.

OBJECTIVES

To evaluate whether zinc supplements prevent OM in adults and children of different ages.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2012, Issue 1) which includes the Cochrane Acute Respiratory Infections Groups' Specialised Register, MEDLINE (1950 to February week 1, 2012) and EMBASE (1974 to February 2012).

SELECTION CRITERIA

Randomised, placebo-controlled trials of zinc supplements given at least once a week for at least a month for preventing OM.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and methodological quality of the included trials and extracted and analysed data. We summarised results using risk ratios (RRs) or rate ratios for dichotomous data and mean differences (MDs) for continuous data. We combined trial results where appropriate.

MAIN RESULTS

We identified 12 trials for inclusion, 10 of which contributed outcomes data. There was a total of 6820 participants. In trials of healthy children living in low-income communities, two trials did not demonstrate a significant difference between the zinc supplemented and placebo groups in the numbers of participants experiencing an episode of definite OM during follow-up (3191 participants); another trial showed a significantly lower incidence rate of OM in the zinc group (rate ratio 0.69, 95% confidence interval (CI) 0.61 to 0.79, n = 1621). A small trial of 39 infants undergoing treatment for severe malnutrition suggested a benefit of zinc for the mean number of episodes of OM (mean difference (MD) -1.12 episodes, 95% CI -2.21 to -0.03). Zinc supplements did not seem to cause any serious adverse events but a small minority of children were reported to have vomited shortly after ingestion of the supplements. The trial evidence included is generally of good quality, with a low risk of bias.

AUTHORS' CONCLUSIONS

Evidence on whether zinc supplementation can reduce the incidence of OM in healthy children under the age of five years living in low- and middle-income countries is mixed. There is some evidence of benefit in children being treated for marasmus (severe malnutrition) but this is based on one small trial and should therefore be treated with caution.

Infections and immunodeficiency in Down syndrome

Down syndrome (DS) is the most common genetic disease and presents with cognitive impairment, cardiac and gastrointestinal abnormalities, in addition to other miscellaneous clinical conditions. DS individuals may have a high frequency of infections, usually of the upper respiratory tract, characterized by increased severity and prolonged course of disease, which are partially attributed to defects of the immune system. The abnormalities of the immune system associated with DS include: mild to moderate T and B cell lymphopenia, with marked decrease of naive lymphocytes, impaired mitogen-induced T cell proliferation, reduced specific antibody responses to immunizations and defects of neutrophil chemotaxis. Limited evidence of genetic abnormalities secondary to trisomy of chromosome 21 and affecting the immune system is available, such as the potential consequences of gene over-expression, most significantly SOD1 and RCAN1. Secondary immunodeficiency due to metabolic or nutritional factors in DS, particularly zinc deficiency, has been postulated. Non-immunological factors, including abnormal anatomical structures (e.g. small ear canal, tracheomalacia) and gastro-oesophageal reflux, may play a role in the increased frequency of respiratory tract infections. The molecular mechanisms leading to the immune defects observed in DS individuals and the contribution of these immunological abnormalities to the increased risk of infections require further investigation. Addressing immunological and non-immunological factors involved in the pathogenesis of infectious diseases may reduce the susceptibility to infections in DS subjects.

Zinc supplements for preventing otitis media

BACKGROUND

Otitis media (inflammation of the middle ear, usually caused by infection) affects people of all ages, but is particularly common in young children. Around 164 million people worldwide have long-term hearing loss caused by this condition, 90% of them in low-income countries. Because zinc supplements prevent pneumonia in disadvantaged children, we wondered whether they prevent otitis media.

OBJECTIVES

To evaluate whether zinc supplements prevent otitis media in adults and children of different ages.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2) which includes the Acute Respiratory Infection Groups' Specialised Register; MEDLINE (1950 to June Week 1 2009); and EMBASE (1974 to June 2009).

SELECTION CRITERIA

Randomised, placebo-controlled trials of zinc supplements given at least once a week for at least a month for preventing otitis media.

DATA COLLECTION AND ANALYSIS

Two review authors assessed the eligibility and methodological quality of the included trials, extracted and analysed data and wrote the review. We summarised results using risk ratios or rate ratios for dichotomous data and mean differences for continuous data. We combined trial results where appropriate.

MAIN RESULTS

We identified 12 trials for inclusion, 10 of which contributed outcomes data. In trials of healthy children living in low-income communities, two trials did not demonstrate a significant difference between the zinc supplemented and placebo groups in the numbers of participants experiencing an episode of definite otitis media during follow up (3191 participants), while another trial showed a significantly lower incidence rate of otitis media in the zinc group (rate ratio 0.69, 95% confidence interval (CI) 0.61 to 0.79, n = 1621). A small trial of 39 infants undergoing treatment for severe malnutrition suggested a benefit of zinc on the mean number of episodes of otitis media (mean difference -1.12 episodes, 95% CI -2.21 to -0.03). Zinc supplements did not seem to cause any serious adverse events, but a small minority of children were reported to have vomited shortly after ingestion of the supplements.

AUTHORS' CONCLUSIONS

Evidence on whether zinc supplementation can reduce the incidence of otitis media in healthy children under the age of five years living in low- and middle-income countries is mixed. There is some evidence of benefit in children being treated for marasmus, but this is based on one small trial and should therefore be treated with caution.

Zinc supplementation for the treatment or prevention of disease: current status and future perspectives

Zinc is a nutritionally essential trace element, and thus zinc deficiency may severely affect human health. Many studies were published in which the effect of nutritional zinc supplementation on the incidence or severity of a certain disease was investigated. This review summarizes the main observations and aims to evaluate the use of nutritional zinc supplementation for prevention and treatment of human disease.

Aspectos metabólicos e funcionais do zinco na síndrome de Down

Este estudo relata os aspectos funcionais do zinco, bem como a participação desse mineral nas alterações metabólicas presentes em indivíduos portadores de Síndrome de Down. A maioria dos trabalhos realizados observou que o estado nutricional relativo ao zinco nesses pacientes está inadequado, com alterações no sistema antioxidante, imunológico e no metabolismo dos hormônios da tireóide. Estudos in vitro apontam que o zinco participa como cofator da enzima deiodinase tipo II na conversão periférica de Tiroxina em Triiodotironina, e que essa reação está diminuída em indivíduos portadores de Síndrome de Down, o que contribui para a manifestação de distúrbios, como o hipotireoidismo subclínico. As alterações na compartimentalização do zinco no organismo desses indivíduos também favorecem a expressão excessiva da enzima cobre/zinco (Cu/Zn) superóxido dismutase, com aumento do estresse oxidativo, e ainda alterações no sistema imune. Na Síndrome de Down, tem sido demonstrada melhora no metabolismo dos hormônios tireoidianos e na função imune, após a suplementação com zinco. Portanto, o papel metabólico do zinco na Síndrome de Down deve ser mais pesquisado, tendo em vista que esse mineral pode contribuir no controle das alterações metabólicas comumente presentes em indivíduos portadores dessa síndrome.

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.

Complementary and alternative therapies for Down syndrome

In their role as committed advocates, parents of children with Down syndrome have always sought alternative therapies, mainly to enhance cognitive function but also to improve their appearance. Nutritional supplements have been the most frequent type of complementary and alternative therapy used. Cell therapy, plastic surgery, hormonal therapy, and a host of other therapies such as massage therapy have been used. There is a lack of well-designed scientific studies on the use of alternative therapies in individuals with Down syndrome. Antioxidants hold theoretical promise for treatment of the cognitive, immune, malignancy, and premature aging problems associated with Down syndrome. Medications for treatment of Alzheimer's disease may also result in benefit for the population of individuals with Down syndrome.

Nasal ciliary function and ultrastructure in Down syndrome

OBJECTIVES/HYPOTHESIS

To investigate the in vivo nasal ciliary beat and the ciliary ultrastructure in Down syndrome because, although in this condition an increased susceptibility to respiratory tract infections has been reported by several authors, the nature of this phenomenon is not fully understood.

STUDY DESIGN

Experimental study of 18 subjects with Down syndrome and 18 healthy control subjects.

METHODS

Ciliary beat frequency (CBF) was measured on samples of ciliated epithelium obtained from the inferior nasal turbinate; a further brushing for ultrastructural analysis was performed only in subjects showing a CBF reduction or a ciliary movement alteration.

RESULTS

The mean CBF in the group with Down syndrome was 7 +/- 2.82 Hz, and in the control subjects it was 10.94 +/- 0.65 Hz. In the same 66.6% of subjects with Down syndrome, we observed a fibrillatory movement of cilia and no metachronicity was present. Moreover, in 14 subjects with Down syndrome as hyperproduction of mucus was present. Ultrastructural evaluation at transmission election microscopy instead revealed a normal architecture of cilia.

CONCLUSION

We attribute the nature of the mucociliary defect in Down syndrome to recurrent respiratory tract infections causing changes in mucus properties as in rheological parameters and not to a primitive defect of cilia.

Zinc, infections and immunosenescence

Infections may cause mortality in old age due to damaged immune responses. As zinc is required as a catalyst, structural (zinc fingers) and regulatory ion, it is involved in many biological functions, including immune responses. Low zinc ion bioavailability and impaired cell-mediated immunity are common in ageing and may be restored by physiological supplementation with zinc for 1-2 months, impacting upon morbidity and survival. This article reviews the role of zinc in immune efficacy during ageing, and also describes the main biochemical pathways involved in the role of zinc in resistance to infections in ageing in order to better understand the possible causes of immunosenescence.

Epidemiologic studies of childhood leukemia: where do we go from here?

Much of our knowledge of the mechanisms of carcinogenesis has resulted from the study of rare cancers, including retinoblastoma, angiosarcoma, and vaginal clear cell carcinoma. Due to the heterogeneity of childhood leukemia, epidemiologic studies that focus on children with unique clinical and genetic manifestations of the disease could potentially lead to further understanding of leukemogenesis.

Normalization of cellular zinc levels in patients with Downs syndrome does not always correct low thymulin levels

Retrospective analysis of five Down's syndrome (DS) patients who presented with recurrent infection revealed that all had initial low thymulin levels. Three patients had low cellular zinc levels that normalized after zinc replacement. Contrary to previous studies, thymulin levels were persistently low in four of five DS patients despite maintaining or achieving normal cellular zinc levels. A primary thymic epithelial defect may be responsible for the persistent thymulin deficiency in DS patients.

Benefit of oral zinc supplementation as an adjunct to zidovudine (AZT) therapy against opportunistic infections in AIDS

Zinc is perhaps the most important trace element for immune function. Congenital or acquired zinc deficiencies are associated with immune abnormalities and increased susceptibility to infectious diseases. AIDS subjects suffer from reduced zinc bioavailability, more severe in stage IV than in stage III. Such zinc deficiency causes, among other effects, a profound reduction in the biological activity of one of the thymic hormones, thymulin (zinc-facteur-timique-serique, ZnFTS). With these premises, zinc sulphate was administered orally at a daily dose of 200 mg for 30 days to AZT-treated stage III subjects with generalized lymphadenopathy (17 subjects) and stage IV subgroup C1 (12 subjects) AIDS patients. 18 stage III subjects with generalized lymphoadenopathy and 10 stage IV subgroup C1 subjects treated only with AZT served as controls. Zinc sulphate supplementation of stage III and in stage IV C1 patients was followed by an increase or a stabilization in the body weight and an increase of the number of CD4+ cells and the plasma level of active zinc-bound thymulin. The frequency of opportunistic infectious episodes in the 24 months following entry into the study was reduced after zinc supplementation in stage IV C1 subjects (11 infections vs 25 in controls) and delayed in stage III zinc-treated subjects (1 infection/24 months vs 13 infections/24 months in controls). The effect of zinc on opportunistic infections is restricted to infections due to Pneumocystis carinii and Candida, whereas no variations have been observed in the frequencies of cytomegalovirus and toxoplasma infections. These data may support the benefit of zinc as an adjunct to AZT therapy in AIDS pathology.

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.

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.