In vitro studies of lymphocytes from children with kwashiorkor

The immune system in children with malnutrition--a systematic review

BACKGROUND

Malnourished children have increased risk of dying, with most deaths caused by infectious diseases. One mechanism behind this may be impaired immune function. However, this immune deficiency of malnutrition has not previously been systematically reviewed.

OBJECTIVES

To review the scientific literature about immune function in children with malnutrition.

METHODS

A systematic literature search was done in PubMed, and additional articles identified in reference lists and by correspondence with experts in the field. The inclusion criteria were studies investigating immune parameters in children aged 1-60 months, in relation to malnutrition, defined as wasting, underweight, stunting, or oedematous malnutrition.

RESULTS

The literature search yielded 3402 articles, of which 245 met the inclusion criteria. Most were published between 1970 and 1990, and only 33 after 2003. Malnutrition is associated with impaired gut-barrier function, reduced exocrine secretion of protective substances, and low levels of plasma complement. Lymphatic tissue, particularly the thymus, undergoes atrophy, and delayed-type hypersensitivity responses are reduced. Levels of antibodies produced after vaccination are reduced in severely malnourished children, but intact in moderate malnutrition. Cytokine patterns are skewed towards a Th2-response. Other immune parameters seem intact or elevated: leukocyte and lymphocyte counts are unaffected, and levels of immunoglobulins, particularly immunoglobulin A, are high. The acute phase response appears intact, and sometimes present in the absence of clinical infection. Limitations to the studies include their observational and often cross-sectional design and frequent confounding by infections in the children studied.

CONCLUSION

The immunological alterations associated with malnutrition in children may contribute to increased mortality. However, the underlying mechanisms are still inadequately understood, as well as why different types of malnutrition are associated with different immunological alterations. Better designed prospective studies are needed, based on current understanding of immunology and with state-of-the-art methods.

The ontogeny of the gut mucosal immune system and the susceptibility to infections in infants of developing countries

In this review we summarize data on the human gut mucosa associated lymphatic tissues as part of the common mucosal immune system. Its embryonal-fetal and post-natal ontogeny becomes severely distorted and compromised by mal-/undernutrition which is so prevalent in developing countries. Pathogenetic interdependencies exist between maternal-fetal undernutrition, the ontogeny of the immune system, constant antigenic stimulation of the mucosal immune system post-natally, and the 14 million deaths annually from infections in children below the age of 5 years in developing countries. A detailed knowledge of these interdependencies is required for effective prevention and treatment in an attempt to reduce the high morbidity and mortality rates of children in developing countries.

Paediatric oncology in developing countries

Paediatric oncology in developing countries is a specialty in its own right that has so far been largely neglected by the western medical profession. It has specific features of genetic cancer predisposition and of external factors influencing phenotypic cancer manifestations. We point out here some of the specific features of cancer presentation in children of developing countries.

Phagocytosis and resistance to Salmonella typhimurium infection in mice fed with lipidic diet

The peritoneal macrophages from mice on a lipidic diet have shown an increase of surface hydrophobicity of cytoplasmatic membrane. This fact is correlated with a decrease of the phagocytic index and with an impairment of Salmonella typhimurium.

Soluble immune complexes, acute phase proteins and E-rosette inhibitory substance in sera of malnourished children

The percentage of circulating E-rosetting lymphocytes and the presence of serum E-rosette inhibitory substance were determined in 58 marasmic, 13 kwashiorkor and 22 well-fed children. The blood levels of soluble immune complexes and some acute phase proteins were also measured. The percentage of E-rosetting lymphocytes was significantly higher in the well-fed than in the malnourished children. The presence of the inhibitory substance in serum correlated with depressed levels of circulating mean percentage E-rosetting lymphocytes. Elevation in the level of soluble immune complexes was observed to correlate closely with the presence of serum E-rosette inhibitory substance and with a diminished percentage of E-rosetting lymphocytes. There was no significant correlation between the percentage of circulating E-rosetting lymphocytes and the serum alpha 1 antitrypsin, alpha 2 macroglobulin or C-reactive protein levels. It is suggested that at high serum concentrations soluble immune complexes may bind selectively to human T lymphocytes in vivo, thereby inhibiting the latter's ability to form E-rosettes in vitro.

Impairment of macrophage migration inhibitory factor synthesis and macrophage migration in protein-malnourished mice

Weanling CD2F1 mice were fed isocaloric diets that were protein sufficient (PS; containing 27% casein) or protein deficient (PD; containing 8% casein). Weight measurements demonstrated that the growth of PD mice was significantly impaired, thus indicating that the PD diet induced protein malnutrition. The cellular immune responsiveness of these mice was assessed from Day 21 to Day 49 of the diet using, as indicators, in vitro production of migration inhibitory factor (MIF) by splenic lymphocytes and MIF responsiveness of peritoneal macrophages. PD lymphocytes, when stimulated with the polyclonal activator concanavalin A, produced significantly less MIF than did PS lymphocytes. The amount of MIF produced by PD lymphocytes, however, increased throughout the study, possibly indicating delayed maturation of MIF synthetic capacity in PD mice. Normal CD2F1 mouse macrophages were used for these assays. MIF responsiveness of PD and PS macrophages was not significantly different when assayed using MIF produced by normal CD2F1 mouse lymphocytes. As compared to that of PS macrophages, the migratory ability of PD macrophages decreased progressively throughout the study. This impaired migratory ability did not interfere with MIF responsiveness of PD macrophages.

Immune function in the malnourished host

Deficiencies of protein, energy, and specific vitamins and minerals impair function of various components of the immunological network and therefore weaken host defense. These various deficiencies may affect specific loci within the network, but because of the interrelations between the different systems, the ultimate effect may be quite broad. Patients with PEM often suffer infections, which may also impair the immune function. It is difficult to separate effects of malnutrition from those of infection, a fact recognized in the recent coinage of the term malnutrition-infection complex. On the basis of the available information it appears that PEM and associated deficiencies of nutrients cause a major impairment in the T lymphocytes and the complement system. They have relatively less effect on the B lymphocytes and the phagocytes directly; however, normal B cell activity is dependent on regulatory influences of T cells and the phagocytic cells require mediators generated from the activation of complement. Therefore these cells also are functionally defective in PEM. The consequence of these deficiencies of function of the immune system in the malnourished host is heightened susceptibility to and a less vigorous response to infections. These defects can be generally reversed by nutritional rehabilitation.

T and B lymphocyte function in response to a protein-free diet

Groups of female adult rats were fed either isocaloric protein-free or 18% protein diets for various intervals. Four days before sacrifice, the animals were immunized either with sheep erythrocytes or with a trinitrophenyl-lipopolysaccharide (TNP-LPS) conjugate. Spleen lymphoid cell populations, spleen plaque-forming cells, and serum hemolysins were measured. A persistent diminution, proportional to the duration of protein deprivation, was observed in all parameters studied after immunization with the T-dependent antigen, sheep erythrocytes. The immune dysfunction was more pronounced for hemolysin titers, which became undetectable after 15 days of protein-free diet. The response of the protein-free group to the T-independent antigen (TNP-LPS) after 15 days of diet was only 34% of the control. When a T-cell lymphokine, macrophage migration inhibitory factor, was measured, a normal response was observed in the protein-free group. Feeding a normal diet rapidly restored the spleen plaque-forming cell populations to 60% of normal after 4 days and to 100% after 6 days. Protein starvation influenced the production of antibodies more than it did the number of antibody-forming cells. The nutritional impairment of immunoglobulin synthesis appears to be reversible.

Alteration of cell-mediated immunity to Listeria monocytogenes in protein-malnourished mice treated with thymosin fraction V

Cell-mediated immune reactivity, measured by lymphocyte responsiveness to phytohemagglutinin, was higher in both young or aged mice fed a 4% casein diet compared with age-matched controls. Treatment in vivo with bovine thymosin fraction V decreased the responsiveness to phytohemagglutinin of lymphocytes from mice fed either the control or moderately protein-deficient diets when compared with mice treated in vivo with saline. Resistance against Listeria monocytogenes, known to be a cell-mediated immune function, was impaired in young and aged mice which were fed the low-protein diet. Treatment with thymosin was able to significantly improve the cell-mediated immune resistance to L. monocytogenes of moderately protein-malnourished mice. Thymosin treatment impaired the resistance to L. monocytogenes of young or aged mice fed the control diet. The splenic natural killer cell cytotoxicity of protein-malnourished mice was impaired compared with that of mice fed the control diet. Treatment with thymosin did not restore the natural killer cell cytotoxic activity in protein-malnourished mice, but did enhance that activity in control mice.

Lymphocyte proliferation kinetics in malnourished children measured by differential chromatid staining

1. Utilizing the bromodeoxyuridine differential-chromatid labelling technique the in vitro proliferation of lymphocytes from children with kwashiorkor was followed in phytohaemagglutinin-stimulated cultures and compared with controls. 2. Analyses of first, second and third or subsequent division cells as a function of culture time between 40 and 96 h showed that cell-cycle duration was prolonged in kwashiorkor cultures. The extent of this increase was approximately 4.5 h for the first-division cells and 1.5 h for third-division cells. 3. The peak for second-division cells was depressed in kwashiorkor cultures. 4. A decreased number of third or subsequent-division cells was observed in kwashiorkor cultures at all time points studied. 5. These findings suggest that the loss in lymphocyte activity to PHA in malnourished children in general could be due to an increase in cell-cycle duration of responding lymphocytes.

Host defense mechanisms in protein energy malnutrition

This review has focused on effects of protein energy malnutrition on immune responses in the human host. These studies document major impairment of the T-cell and complement systems in severe PEM, and less profound, but probably significant, effects upon B-cells and immunoglobulins, particularly SIgA. While mild-moderate malnutrition also alters the T-cell system and may predispose to infection, there is less evidence to suggest that complement is similarly affected. Indeed, some data suggest that the host with mild to moderate malnutrition is still able to respond to stress with an acute phase serum protein response and to boost serum levels of complement and complement activity. This may be a functionally significant distinction, serving to separate the more from the less severely ill. Because many other factors alter immune responses, including vitamins, calories, and trace metals, and few clinical studies have examined these parameters, it is uncertain how much of the problem in malnutrition is due to protein, to energy intake, to iron, to other micronutrients and trace minerals, to vitamin E or to other vitamins alone or in combination with deficiencies in protein and energy. Other chapters in this volume attempt to sort out these questions in animal studies, but the relevance of these data for the human situation will remain uncertain until the investigations are carried out in humans as well.

Lymphocyte populations in maintenance hemodialysis patients - reassessment and analysis of B cell subtypes

Maintenance hemodialysis patients are known to be lymphopenic, and it was previously felt that T and B cells were equally and moderately depressed. With modification of the B cell technique, however, we have shown that MHD patients have a relatively more pronounced depression of B cells, with decreased proportions and markedly reduced total numbers. B cells bearing specific immunoglobulin types are all proportionally reduced. This marked B cell deficiency could be responsible for the increased rate of some infections in MHD subjects. Its relationship to azotemia, malnutrition, toxic or deficiency states, or dialysis itself is unknown, and the stages of cellular maturation or interaction which are affected have not been identified.