The mammary gland-infant intestine immunologic dyad

Breast feeding, obesity, and asthma association: clinical and molecular views

Asthma is a chronic condition that affects children worldwide. Accumulating number of studies reported that the prevalence of pediatric obesity and asthma might be altered through breastfeeding. It has been proposed that Leptin, which exists in human milk, is oppositely associated with weight increase in newborns. It may also influence peripheral immune system by promoting TH1 responses and suppressing TH2 cytokines. Leptin influences body weight and immune responses through complex signaling pathways at molecular level. Although previous studies provide explanations for the protective role of breastfeeding against both obesity and asthma, other factors such as duration of breastfeeding, parental, and prenatal factors may confound this relationship which requires further research.

Escherichia Coli Specific Secretory IgA and Cytokines in Human Milk from Mothers of Different Ethnic Groups Resident in Northern Italy

Breast milk supplies many bioactive components. Neonates protection from pathogenic bacteria is mainly attributable to secretory IgA antibodies present in human milk in an amount depending on previous antigenic exposure. To bring new details into the field of immunological memory in secretory immunity, we evaluated the production of s-IgA specific for E. coli (E. coli s-IgA), and of proinflammatory (IL-6 and IL-8) or anti-inflammatory (IL-10) cytokines in the milk of mothers of different ethnic groups exposed in the past to poor conditions, but nowadays living in Italy in adequate conditions. Mothers from Italy, Africa, Asia and Eastern European Countries were included in the study. Anti- E. coli s-IgA, IL-6, IL-8 and IL-10 were determined by ELISA. Breast milk of all the foreign mothers presented higher levels of E. coli s-IgA than Italians, and for Asian and African mothers were significative (p=0.031 and p=0.015, respectively). Milk from women of Eastern European Countries revealed the highest IL-8 levels (p=0.026), while milk from Asian women presented the greatest concentration of IL-6 (p=0.04); however, the Africans reported the lowest concentrations of IL-10 (p=0.045). Since all the mothers had been living in Italy for some time, we believe that the presence of high levels of E. coli s-IgA, supported by high levels of pro-inflammatory cytokine, is part of a persisting immunological secretory memory.

The role of the lactadherin in promoting intestinal DCs development in vivo and vitro

Lactadherin, as one of the immune components in the breast milk, might play a role in the intestinal immune system of newborn. Therefore, we investigated the effect of lactadherin-feeding in early time on the development of intestinal immune system compared with naturally rearing and artificially rearing (non-lactadherin). In the present study, we observed that the Peyer's Patches (PP) from the pups of artificially reared group with lactadherin added were characterized by an excess of OX62(+)CD4(+)SIRP(+) DC cells and a higher expression of CD3(+)CD4(+)CD25(+)T cells. Additionally, this study also demonstrated that IL-10 production was dramatically increased when lactadherin was present in culture medium compared with lactadherin-absent culture. These results suggested that lactadherin could adjust intestinal DCs activity, induce CD3(+)CD4(+)CD25(+)T cell differentiation, and enhance IL-10 production.

Host factors in amniotic fluid and breast milk that contribute to gut maturation

The gut represents a complex organ system with regional differences, which reflect selective digestive and absorptive functions that change constantly in response to bodily requirements and the outside milieu. As a barrier to the external environment, gut epithelium must be renewed rapidly and repeatedly. Growth and renewal of gut epithelial cells is dependent on controlled cell stimulation and proliferation by a number of signaling processes and agents, including gut peptides-both endogenous and exogenous sources. This cascade of events begins during fetal development; with the ingestion of amniotic fluid, this process is enhanced and continued during infancy and early childhood through the ingestion of human milk. Events influenced by amniotic fluid during fetal development and those influenced by human milk that unfold after birth and early childhood to render the gut mature are presented.

The relationship of breast-feeding, overweight, and asthma in preadolescents

BACKGROUND

Breast-feeding is suggested to be associated with overweight or asthma in children. Overweight and asthma may share common environmental influences of which breast-feeding may be one.

OBJECTIVE

We evaluated whether short duration of exclusive breast-feeding and subsequent overweight were associated with asthma.

METHODS

A nested case-control study included 246 children with pediatric allergist-diagnosed asthma and 477 controls without asthma at age 8 to 10 years. Information on exclusive breast-feeding was obtained from questionnaire data. Overweight at 8 to 10 years of age was defined as body mass index >/=85th percentile of age and sex-specific growth charts. The association between asthma and exclusive breast-feeding <12 weeks plus overweight, adjusted for sex, parental asthma, aboriginal origin, passive smoking at birth, residence location, and family income, was determined in logistic regression analyses.

RESULTS

Exclusive breast-feeding <12 weeks was closely associated with overweight at age 8 to 10 years (P < .001). Exclusive breast-feeding <12 weeks plus overweight was significantly associated with asthma (adjusted OR, 1.81; 95% CI, 1.11-2.95; P = .018). This association appeared to be strong in children whose mothers had asthma (adjusted OR, 3.93; 95% CI, 1.17-13.2) and also in boys (adjusted OR, 2.22; 95% CI, 1.14-4.34). Asthma was not associated with either exclusive breast-feeding <12 weeks or overweight in the absence of the other.

CONCLUSION

Short duration of exclusive breast-feeding and subsequent overweight are associated with asthma in susceptible children, suggesting a common pathway.

CLINICAL IMPLICATIONS

This finding adds to the importance of promoting prolonged breast-feeding for the prevention of overweight and asthma.

Protection of the neonate by the innate immune system of developing gut and of human milk

The neonatal adaptive immune system, relatively naïve to foreign antigens, requires synergy with the innate immune system to protect the intestine. Goblet cells provide mucins, Paneth cells produce antimicrobial peptides, and dendritic cells (DCs) present luminal antigens. Intracellular signaling by Toll-like receptors (TLRs) elicits chemokines and cytokines that modulate inflammation. Enteric neurons and lymphocytes provide paracrine and endocrine signaling. However, full protection requires human milk. Breast-feeding reduces enteric infection and may reduce chronic disease in later life. Although human milk contains significant secretory immunoglobulin A (sIgA), most of its protective factors are constitutively expressed. Multifunctional milk components are nutrients whose partial digestion products inhibit pathogens. Cytokines, cytokine receptors, TLR agonists and antagonists, hormones, anti-inflammatory agents, and nucleotides in milk modulate inflammation. Human milk is rich in glycans (complex carbohydrates): As prebiotics, indigestible glycans stimulate colonization by probiotic organisms, modulating mucosal immunity and protecting against pathogens. Through structural homology to intestinal cell surface receptors, glycans inhibit pathogen binding, the essential first step of pathogenesis. Bioactive milk components comprise an innate immune system of human milk whereby the mother protects her nursing infant. Interactions between human milk glycans, intestinal microflora, and intestinal mucosa surface glycans underlie ontogeny of innate mucosal immunity, pathobiology of enteric infection, and inflammatory bowel diseases.

Could peripartum antibiotics have delayed health consequences for the infant?

Antibiotics are increasingly prescribed in the peripartum period, for both maternal and fetal indications. Their effective use undoubtedly reduces the incidence of specific invasive infections in the newborn, such as group B streptococcal septicaemia. However, the total burden of infectious neonatal disease may not be reduced, particularly if broad-spectrum agents are used, as the pattern of infections has been shown to alter to allow dominance of previously uncommon organisms. This area has been relatively understudied, and there are almost no studies of long-term outcome. Recent findings suggest that such long-term data should be sought. First, there is evidence that organisms initially colonising the gut at birth may establish chronic persistence in many children, in contrast to prompt clearance if first encountered in later infancy, childhood or adulthood. Second, there is a rapidly advancing basic scientific data showing that individual members of the gut flora specifically induce gene activation within the host, modulating mucosal and systemic immune function and having an additional impact on metabolic programming. We thus review the published data on the impact of perinatal antibiotic regimens upon composition of the flora and later health outcomes in young children and summarise the recent scientific findings on the potential importance of gut flora composition on immune tolerance and metabolism.

Alternative modified infant-feeding practices to prevent postnatal transmission of human immunodeficiency virus type 1 through breast milk: past, present, and future

Preventing mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) through breastfeeding is important to reduce the number of infected children. Research on making breastfeeding safer is a high priority. The authors reviewed the attempts to develop alternative methods, other than antiretroviral (ARV) therapy of mothers and/or babies, to decontaminate breast milk of infectious HIV-1 (free and associated with lymphocytes). They also review how these methods affect milk constituents, as well as their current and prospective status. A PubMed search for English publications on methods to prevent MTCT through breast milk was completed. Methods that have been tested, other than systemicuse or ARV or immunoprophylaxis, to reduce or prevent MTCT of HIV-1 through breast milk were broadly classified into 5 groups: (1) modified feeding practices, (2) heat treatment of milk, (3) lipolysis, (4) antimicrobial treatment of the breastfeeding mother, and (5) microbicidal treatment of infected milk. Their advantages and disadvantages are discussed, as well as future directions in the prevention of MTCT through breastfeeding.

Infant mouthing behavior: the immunocalibration hypothesis

Avid mouthing, the propensity of infants to suck objects and put them in their mouths, is a pattern characteristic of the first 2-3 years of life, with its most intensive manifestation occurring during the first year. Although traditional accounts explain infant mouthing as a source of sensual gratification and/or environmental exploration, these proximate hypotheses are inconsistent with the high costs of mouthing, including choking, poisoning, and exposure to pathogens. We propose that mouthing serves to proactively expose the naive gastrointestinal tract to environmental antigens and commensal bacteria while under the sheltering umbrella of breastfeeding. Mouthing functions to accurately calibrate the developing immune system, including antibody production and mucosal immunity, to the local disease ecology. The critical exposure period is not open-ended, as failure to expose the gut to an adequate number of antigens early in life is associated with an increased risk of allergies, asthma, and atopy. Weaning initiates a number of immune changes that may program the neonatal immune system into certain life-long responses.

Neonatal leptin levels are strongly associated with female gender, birth length, IGF-I levels and formula feeding

OBJECTIVE

To investigate predictors of circulating leptin in healthy full-term newborns and to explore the relationship with anthropometric variables, serum levels of adiponectin and the major components of the IGF system at birth. To explore whether leptin levels are regulated by breastfeeding vs. formula feeding.

DESIGN

Observational cross-sectional study.

PATIENTS

Three hundred and nineteen healthy full-term newborns delivered during 1999 in Athens, Greece.

MEASUREMENTS

Anthropometric measurements, formula feeding information and blood samples were obtained. Leptin and adiponectin determinations were performed using a radioimmunoassay (RIA).

RESULTS

Multivariate regression analyses showed that leptin levels were positively associated with female gender, newborn length, ponderal index and IGF-I levels, but not with adiponectin levels. Newborns who were fed exclusively with milk formulas had more than twice the leptin levels of those who were exclusively breastfed.

CONCLUSIONS

Leptin levels are positively related to female gender and anthropometric characteristics of neonates but, contrary to studies in adults, are not correlated with adiponectin levels. We also found evidence that formula feeding imparts a considerable increase in leptin levels in newborns.

Breast milk and infection

Three viruses (CMV, HIV, and HTLV-I) frequently cause infection or disease as a result of breast-milk transmission. Reasonable guidelines have been pro-posed for when and how to avoid breast milk in the case of maternal infection. For other viruses, prophylactic immune therapy to protect the infant against all modes of transmission are indicated (VZV, varicella-zoster immunoglobulin, HAV and immunoglobulin, HBV, and HBIg + HBV vaccine). In most maternal viral infections, breast milk is not an important mode of transmission, and continuation of breastfeeding is in the best interest of the infant and mother (see Tables 2 and 3). Maternal bacterial infections rarely are complicated by transmission of infection to their infants through breast milk. In a few situations, temporary cessation of breastfeeding or the avoidance of breast milk is appropriate for a limited time (24 hours for N gonorrheae, H infiuenzae, Group B streptococci, and staphylococci and longer for others including B burgdorferi, T pallidum, and M tuberculosis). In certain situations, prophylactic or empiric therapy may be advised for the infant (eg, T pallidum, M tuberculosis, H influenzae) (see Table 1). Antimicrobial use by the mother should not be a reason not to breastfeed. Alternative regimens that are compatible with breastfeeding can be chosen to treat the mother effectively. In most cases of suspected infection in the breastfeeding mother, the delay in seeking medical care and making the diagnosis means the infant has been ex-posed already. Stopping breastfeeding at this time only deprives the infant of the nutritional and potential immunologic benefits. Breastfeeding or the use of expressed breast milk, even if temporarily suspended, should be encouraged and supported. Decisions about breast milk and infection should balance the potential risk compared with the innumerable benefits of breast milk.

The prospects of modifying the antimicrobial properties of milk

Milk contains a variety of substances, which inhibit the infection of pathogens. This is of benefit to the mother, safeguarding the integrity of the lactating mammary gland, but also of huge importance for protection of the suckling offspring. The antimicrobial substances in milk can be classified into two categories. First, nonspecific, broad-spectrum defense substances, which have evolved over long periods of time, and secondly, substances like antibodies, which are specifically directed against particular pathogens and have developed during the mother's lifetime. Substances in both categories may be targets for biological intervention and manipulation with the goal of improving the antimicrobial properties of milk. These alterations of milk composition have applications in human as well as in animal health.

Ribosomal immunotherapy for recurrent respiratory tract infections in children

Recurrent respiratory tract infections are common in children. They reflect the immaturity of the immune system in its encounter with environmental antigens. Little or no specific protective immune response has yet been established. These infections represent an important public health problem in terms of both treatment (anti-inflammatory or antibacterial drugs for children) and economy. Immunotherapy has been proposed as a means of preventing these recurrent infections by providing children with small doses of inactive bacterial antigens liable to trigger specific and protective immune responses. Among such drugs, ribosomal preparations (to which this review is limited) appear to be not only well tolerated, but also ideally targeted to induce mucosal responses. One preparation of ribosomal mucosal vaccine is commercially available in several countries. Numerous clinical trials in the world have confirmed the positive role of this mucosal ribosomal bacterial vaccine in significantly reducing the number of infections, courses of antibacterials, and absenteeism. In vitro and ex vivo investigations have confirmed that such vaccines indeed trigger protective specific immune responses.

Presence of bovine leptin in edible commercial milk and infant formula

Leptin is a hormone secreted by the adipocytes that contribute to the control of energy balance, and circulating leptin levels reflect the amount of adipose tissue in the body, helping to regulate food intake and energy expenditure. Since it has been shown that human milk contains immunoreactive leptin, which is identical to intact human leptin, we decided to investigate the possible presence of immunoreactive bovine leptin in different kinds of common commercial milk. To determine the presence or absence of immunoreactive leptin in bovine milk for human consumption, 81 samples (66 commercial pasteurized milk and 15 artificial formulae for new-born babies) of the most common Spanish commercial types of milk were studied. All samples were evaluated before and after centrifugation, and leptin levels were measured by RIA. Leptin was detected in all samples and RIA standard curves were not perturbed when centrifuged and non-centrifuged milk replaced the buffer. Mean values of leptin in full-cream, semi-skimmed and skimmed samples, were: 5.7+/-0.3 ng/ml, 4.1+/-0.1 ng/ml, 3.7+/-0.1 ng/ml (significantly different). Leptin values were reduced after centrifugation. A significant correlation was observed between leptin levels and lipid content (p<0.0005, r=0.67) while no correlation was observed with respect to carbohydrate and protein levels. Interestingly, some preparations of infant formulae present very high leptin values reaching up to 18.9 ng/ml. In conclusion, leptin is present in significant and variable concentrations in edible commercial bovine milk, with higher concentrations in infant formula.

Serum leptin levels and anthropometric correlates in Ache Amerindians of eastern Paraguay

Leptin is a recently discovered peptide hormone secreted primarily from adipocytes in humans and other mammals; it is a reflection of fat stores, and has been associated with reproductive function. However, few leptin measurements are available from nonindustrialized populations, including contemporary hunter/gatherer communities undergoing the transition to sedentary agriculture. This investigation reports single-sample serum leptin measurements in healthy Ache Amerindian males (n = 21; average age, 32.8 +/- 3.4 SE) and females (n = 12; average age, 31.3 +/- 4.3) in eastern Paraguay. Ache leptin concentrations were much lower than in industrialized populations, although significant sexual dimorphism was evident (female 5.64 ng/ml +/- 0.91 SE vs. male 1.13 ng/ml +/- 0.08; P < 0.0001). Indeed, female leptin levels were similar to those of anorexic women, despite apparently adequate adiposity. Controlling for fat percentage, no significant sex difference was evident, suggesting that adiposity was the primary source of leptin variation. Body fat percentage was highly correlated with leptin in females (r2 = 0.72; P < 0.0005) but not males, who exhibited a modest negative correlation (r2 = 0.25; P < 0.03). Weight (r2 = 0.45; P = 0.02) and BMI (kg/m2) (r2 = 0.81; P < 0.0001) were also significantly correlated in females but not males. These results suggest that: 1) clinical leptin norms based on industrialized populations may represent the highest range of human variation and may not be representative of most human populations; 2) hormonal priming may underlie population variation in leptin profiles; and 3) the relative importance of leptin as a proximate mechanism regulating reproductive effort during human evolution may have been modest.