Mucosal immunity: the immunology of breast milk

Glycerol Monolaurate Contributes to the Antimicrobial and Anti-inflammatory Activity of Human Milk

Human milk has antimicrobial compounds and immunomodulatory activities. We investigated glycerol monolaurate (GML) in human milk versus bovine milk and infant formula for antimicrobial and anti-inflammatory activities. Human milk contained approximately 3000 µg/ml of GML, compared to 150 μg/ml in bovine milk and none in infant formula. For bacteria tested (Staphylococcus aureus, Bacillus subtilis, Clostridium perfringens, Escherichia coli), except Enterococcus faecalis, human milk was more antimicrobial than bovine milk and formula. The Enterococcus faecalis strain, which was not inhibited, produced reutericyclin, which is an analogue of GML and functions as a growth stimulant in bacteria that produce it. Removal of GML and other lipophilic molecules from human milk by ethanol extraction resulted in a loss of antibacterial activity, which was restored by re-addition of GML. GML addition caused bovine milk to become antimicrobial. Human milk but not bovine milk or formula inhibited superantigen and bacterial-induced IL-8 production by model human epithelial cells. GML may contribute beneficially to human milk compared to bovine milk or infant formula.

An Infant Mouse Model of Influenza Virus Transmission Demonstrates the Role of Virus-Specific Shedding, Humoral Immunity, and Sialidase Expression by Colonizing Streptococcus pneumoniae

The pandemic potential of influenza A viruses (IAV) depends on the infectivity of the host, transmissibility of the virus, and susceptibility of the recipient. While virus traits supporting IAV transmission have been studied in detail using ferret and guinea pig models, there is limited understanding of host traits determining transmissibility and susceptibility because current animal models of transmission are not sufficiently tractable. Although mice remain the primary model to study IAV immunity and pathogenesis, the efficiency of IAV transmission in adult mice has been inconsistent. Here we describe an infant mouse model that supports efficient transmission of IAV. We demonstrate that transmission in this model requires young age, close contact, shedding of virus particles from the upper respiratory tract (URT) of infected pups, the use of a transmissible virus strain, and a susceptible recipient. We characterize shedding as a marker of infectiousness that predicts the efficiency of transmission among different influenza virus strains. We also demonstrate that transmissibility and susceptibility to IAV can be inhibited by humoral immunity via maternal-infant transfer of IAV-specific immunoglobulins and modifications to the URT milieu, via sialidase activity of colonizing Streptococcus pneumoniae Due to its simplicity and efficiency, this model can be used to dissect the host's contribution to IAV transmission and explore new methods to limit contagion.IMPORTANCE This study provides insight into the role of the virus strain, age, immunity, and URT flora on IAV shedding and transmission efficiency. Using the infant mouse model, we found that (i) differences in viral shedding of various IAV strains are dependent on specific hemagglutinin (HA) and/or neuraminidase (NA) proteins, (ii) host age plays a key role in the efficiency of IAV transmission, (iii) levels of IAV-specific immunoglobulins are necessary to limit infectiousness, transmission, and susceptibility to IAV, and (iv) expression of sialidases by colonizing S. pneumoniae antagonizes transmission by limiting the acquisition of IAV in recipient hosts. Our findings highlight the need for strategies that limit IAV shedding and the importance of understanding the function of the URT bacterial composition in IAV transmission. This work reinforces the significance of a tractable animal model to study both viral and host traits affecting IAV contagion and its potential for optimizing vaccines and therapeutics that target disease spread.

The best of intentions: Prenatal breastfeeding intentions and infant health

Health organizations recommend that mothers exclusively breastfeed infants for the first six months of life. The current study contributes to a growing body of research that examines whether the purported benefits of breastfeeding are causal. We systematically evaluated the role of an expectant mother's prenatal breastfeeding intentions, which reflect not only demographic characteristics, but also knowledge, attitudes, and social norms about infant feeding, and therefore serve as a proxy for positive maternal selection into breastfeeding. We used the Infant Feeding Practices Study (IFPS) II (n = 1008) to examine a heretofore overlooked group of mothers-those who intended to breastfeed but did not actually breastfeed. Results suggest that mothers who intended to breastfeed had infants with fewer ear infections and respiratory syncytial viruses, and used fewer antibiotics in the first year of life compared to infants whose mothers did not intend to breastfeed, irrespective of whether they actually breastfed. Because breastfeeding intention is a confounding characteristic that proxies for positive maternal selection and does not represent a causal mechanism for infant health, we further examined how mothers who intended to breastfeed differed from mothers who did not intend to breastfeed. Results suggest that mothers who intended to breastfeed had more knowledge about potential food contaminants and consulted more sources of information about nutrition and diet than mothers who did not intend to breastfeed. Taken together, our results underscore the need for new policy interventions aimed at improving infant health.

Vaccines and Antibodies in Relation to Pregnancy and Lactation

With the rapid pace of immunologic research, it is more important than ever for readers to understand rational immunodiagnosis, immunopro-phylaxis, and immunotherapy. This column is intended to help you ensure proper immunologic drug use in your practice.

Comparing the Impact of Topical Application of Human Milk and Chlorhexidine on Cord Separation Time in Newborns

OBJECTIVES

The best umbilical cord care after birth is a controversial issue. Aim of this research was to compare the effect of topical application of human milk and chlorhexidin on cord separation time in newborns.

METHODS

One hundred seventy four neonates attending from hospitals affiliated to Kashan University of Medical Sciences were included. Newborns from birth were randomized to two groups. In group mother's milk, mother will rub her own milk to cord stump two times a day. chlorhexidin (group 2) were applied to the umbilical stump every 12 hours. The time to umbilical cord separation and any discomfort such as infection, hemorrhage, and discharge and odor were documented. Data was analyzed by SPSS software. Independent Samples t-Test, χ(2), Fisher were used in this study.

RESULTS

Results showed a significant statistical difference between cord separation time in two groups and the mean cord separation time in the human milk group (7.15±2.15days) was shorter than the chlorhexidin group (13.28±6.79 days). In addition, a significant correlation was found between Signs of infection (discharge, redness, swelling and odor) in both groups.

CONCLUSIONS

Topical application of breast milk on umbilical cord care leads to quick cord separation time and can be used as easy, cheep, non injury methods for umbilical cord care.

Immune cell-mediated protection of the mammary gland and the infant during breastfeeding

Breastfeeding has been regarded first and foremost as a means of nutrition for infants, providing essential components for their unique growth and developmental requirements. However, breast milk is also rich in immunologic factors, highlighting its importance as a mediator of protection. In accordance with its evolutionary origin, the mammary gland offers via the breastfeeding route continuation of the maternal to infant immunologic support established in utero. At birth, the infant's immune system is immature, and although it was exposed to the maternal microbial flora during pregnancy, it experiences an abrupt change in its microbial environment during and after birth, which is challenging and renders the infant highly susceptible to infection. Active and passive immunity protects the infant via breast milk, which is rich in immunoglobulins, lactoferrin, lysozyme, cytokines, and numerous other immunologic factors, including maternal leukocytes. Breast milk leukocytes provide active immunity and promote development of immunocompetence in the infant. Additionally, it has been speculated that they play a role in the protection of the mammary gland from infection. Leukocytes are thought to exert these functions via phagocytosis, secretion of antimicrobial factors and/or antigen presentation in both the mammary gland and the gastrointestinal tract of the infant, and also in other infant tissues, where they are transported via the systemic circulation. Recently, it has been demonstrated that breast milk leukocytes respond dynamically to maternal as well as infant infections, and are fewer in nonexclusively compared with exclusively breastfeeding dyads, further emphasizing their importance for both the mother and infant. This review summarizes the current knowledge of human milk leukocytes and factors influencing them, and presents recent novel findings supporting their potential as a diagnostic marker for infections of the lactating breast and of the breastfed infant.

Efficacy of topical application of human breast milk on atopic eczema healing among infants: a randomized clinical trial

Infant atopic eczema is an inflammatory lesion usually involving the epidermis of the skin. About 50% of infants are affected by this lesion in the first years of their lives. Studies show human breast milk (HBM) as a preventive measure and effective treatment of some sores and infections. This article evaluates the short-term efficacy of HBM versus hydrocortisone 1% ointment in infants with mild to moderate atopic dermatitis (AD). We conducted a randomized clinical trial among infants with diagnosed AD within a pediatrics unit. The majority of AD cases in both groups were considered moderate severity. There were no significant differences between these two groups at days 0, 7, 14, and 21, and the interventions of both groups were found to have the same effects. The external validity and consequently the ability to generalize the findings may be diminished as this study was conducted in a single site. Owing to HBM and the hydrocortisone 1% ointment providing the same results in the healing of AD, HBM was used because of low cost and accessibility.

On birth single dose live attenuated OPV and BCG vaccination induces gut cathelicidin LL37 responses at 6 week of age: a natural experiment

In a cross sectional study, we show that infants who received single dose of live attenuated OPV and BCG vaccines within 48h of birth, have higher excretion of human cathelicidin LL37 (p<0.05) in stool at 6wk of age. This response remained unchanged in multivariate analysis after adjusting for sex, mode of delivery, infant age, mother age birth weight and breast milk feeding pattern. This analysis also reveals that irrespective of vaccination, girl infants have higher human-beta-defencin2 (HBD2) and exclusively breastfed infants have higher total and anti-polio specific IgA to all three subtypes in stool (p<0.05). However, vaccination induces anti-polio IgA responses only to infants who are exclusively breastfed. Thus on-birth live attenuated vaccination may provide non-specific beneficial effect against infections while exclusive breastfeeding enhance protection by boosting vaccine induced IgA. The result also suggests that in polio endemic area, exclusive breastfeeding may be sufficient for mucosal anti-polio responses during early infancy.

Aetiology and clinical features of dysentery in children aged <5 years in rural Bangladesh

The study identified the common aetiological agents and prominent clinical features of dysentery cases in children aged <5 years and compared this to non-dysentery diarrhoeal cases from the same population. From January 2010 to December 2011, 2324 children aged <5 years received treatment at Kumudini Hospital, of which 682 (29%) presented with dysentery. Of the dysenteric children, aetiology could not be determined for over half (61%). Shigella spp. accounted for 32% of dysentery cases. Significant associations were found between presence of blood in stool and: child age (24-59 months) [odds ratio (OR) 2.21, 95% confidence interval (CI) 1.49-3.27], no treatment of drinking water at home (OR 2.00, 95% CI 1.09-3.67), vomiting (OR 0.19, 95% CI 0.14-0.25), abdominal pain (OR 4.68, 95% CI 3.24-6.77), straining (OR 16.45, 95% CI 11.92-22.69), wasting (OR 1.66, 95% CI 1.15-2.41), and presence of Shigella in stool (OR 6.25, 95% CI 4.20-9.29) after controlling for confounders. This study makes it clear that appropriate public health strategies are needed to reduce the burden of dysentery in Bangladesh.

Differential digestion of human milk proteins in a simulated stomach model

A key element in understanding how human milk proteins support the health and development of the neonate is to understand how individual proteins are affected during digestion. In the present study, a dynamic gastric model was used to simulate infant gastric digestion of human milk, and a subsequent proteomic approach was applied to study the behavior of individual proteins. A total of 413 human milk proteins were quantified in this study. This approach demonstrated a high degree of variability in the susceptibility of human milk proteins to gastric digestion. Specifically this study reports that lipoproteins are among the class of slowly digested proteins during gastric processes. The levels of integral lysozyme C and partial lactadherin in milk whey increase over digestion. Mucins, ribonuclease 4, and macrophage mannose receptor 1 are also resistant to gastric digestion. The retention or enhancement in whey protein abundance can be ascribed to the digestive release of milk-fat-globule-membrane or immune-cell enclosed proteins that are not initially accessible in milk. Immunoglobulins are more resistant to digestion compared to total milk proteins, and within the immunoglobulin class IgA and IgM are more resistant to digestion compared to IgG. The gastric digestion of milk proteins becomes more apparent from this study.

Maternal and infant infections stimulate a rapid leukocyte response in breastmilk

Breastmilk protects infants against infections; however, specific responses of breastmilk immune factors to different infections of either the mother or the infant are not well understood. Here, we examined the baseline range of breastmilk leukocytes and immunomodulatory biomolecules in healthy mother/infant dyads and how they are influenced by infections of the dyad. Consistent with a greater immunological need in the early postpartum period, colostrum contained considerable numbers of leukocytes (13–70% out of total cells) and high levels of immunoglobulins and lactoferrin. Within the first 1–2 weeks postpartum, leukocyte numbers decreased significantly to a low baseline level in mature breastmilk (0–2%) (P<0.001). This baseline level was maintained throughout lactation unless the mother and/or her infant became infected, when leukocyte numbers significantly increased up to 94% leukocytes out of total cells (P<0.001). Upon recovery from the infection, baseline values were restored. The strong leukocyte response to infection was accompanied by a more variable humoral immune response. Exclusive breastfeeding was associated with a greater baseline level of leukocytes in mature breastmilk. Collectively, our results suggest a strong association between the health status of the mother/infant dyad and breastmilk leukocyte levels. This could be used as a diagnostic tool for assessment of the health status of the lactating breast as well as the breastfeeding mother and infant.

DHA supplementation during pregnancy and lactation affects infants' cellular but not humoral immune response

Background. It is currently recommended that diet of pregnant mothers contain 200–300 mg DHA/day. Aim. To determine whether DHA supplementation during pregnancy and lactation affects infants' immune response. Methods. 60 women in ≥3rd pregnancy studied; 30 randomly assigned to receive DHA 400 mg/day from 12th week gestation until 4 months postpartum. From breast-fed infants, blood obtained for anti-HBs antibodies, immunoglobulins, lymphocyte subset phenotyping, and intracellular cytokine production. Results. CD4+ lymphocytes did not differ between groups, but CD4CD45RA/CD4 (naïve cells) significantly higher in infants in DHA+ group. Proportion of CD4 and CD8 cells producing IFN_γ significantly lower in DHA+ group, with no differences in proportion of IL4-producing cells. Immunoglobulins and anti-HBs levels did not differ between groups. Conclusions. In infants of mothers receiving DHA supplementation, a higher percentage of CD4 naïve cells and decreased CD4 and CD8 IFN_γ production is compatible with attenuation of a proinflammatory response.

Exercise is associated with elevated proinflammatory cytokines in human milk

OBJECTIVES

To explore relationships between self-reported exercise in postpartum women and concentrations of cytokines and secretory immunoglobulin A in their milk.

METHOD

Fifty-eight frozen, unthawed aliquots of human hindmilk were available for analysis from a previous larger study on the influence of lactation on postpartum stress and immunity. The samples were early-morning, hand-expressed, hindmilk that had been collected between 4 and 6 weeks. Milk cytokines were analyzed by a multiplex assay of 20 cytokines, chemokines, and growth factors. Milk secretory immunoglobulin A was analyzed by enzyme-linked immunosorbent assay. Exercise data were extracted from a demographic questionnaire that was used in the original study and approximate metabolic-equivalent tasks assigned to the exercise levels reported. Based on reported frequency of exercise at a particular metabolic-equivalent task, caloric expenditures were calculated for each mother.

RESULTS

With increasing metabolic-equivalent tasks, and thus caloric expenditures, proinflammatory cytokines increased in mothers' milk. Secretory immunoglobulin A concentrations were not affected by mother's exercise.

CONCLUSIONS

There are several possible interpretations for these results. These data are preliminary, and a larger, longitudinal study with a more structured exercise instrument will clarify if recommendations should be made about heavy exercise in the early postpartum months.

Leucocytes in human milk and lymphocyte subsets in cow's milk-allergic infants

The breast-fed infant ingests an average of 108 leucocytes per day, with breast-feeding often continuing for several months. The precise role of human milk leucocytes is still unresolved. Breast-feeding has been recommended for infants at high risk of allergy to prevent or delay the development of food allergies and atopic eczema. However, studies dealing with distinct immunologic factors in the mother's milk, and their effect on health status or development of allergies in the infant, are scarce. We evaluated the relationship between the cellular composition of human milk and the development of cow's milk allergy (CMA) in the breast-fed infant. Leucocyte subsets in the breast-fed infants were also measured. The study population comprised 61 breast-feeding mothers and their infants. Thirty-nine mothers each had a cow's milk-allergic infant, 10 had an infant with atopic dermatitis without CMA, and 12 mothers had a healthy infant. Leucocyte subsets in mothers' milk were counted using a light microscope and confirmed by flow cytometry. In infants, peripheral blood lymphocyte subsets were determined by flow cytometry and were correlated with the health status of the breast-fed infant and leucocyte composition of the mother's milk. Human milk was found to be a non-homogenous morphological entity. In the milk of mothers of infants with CMA, the proportion of macrophages was significantly smaller than in the mothers with infants without CMA (p = 0.036, t-test). Mothers with high proportions of neutrophils in their milk (> 20%) had significantly more often infants with CMA than did those with low proportions of neutrophils (p = 0.02; Fischer's exact test). Eosinophils comprising > 1% of milk cells were only detected in the mothers who had infants with CMA. Furthermore, the proportions of CD4+ T cells were positively correlated with the proportion of milk macrophages and negatively with the percentage of milk neutrophils and eosinophils. The proportions of total B cells and those expressing CD23, a low-affinity immunoglobulin E (IgE) receptor, were positively correlated with the proportions of neutrophils and eosinophils in mother's milk and negatively with the percentage of milk macrophages. To conclude, the composition of breast milk in some mothers is abnormal and correlates with a diagnosis of CMA in a breast-fed infant. This may provide a new and interesting insight into the development of food allergies.

Breastfeeding

A large and growing body of scientific evidence suggests that breastfeeding provides immediate and long-lasting health advantages for the mother and her infant. In the United States, breastfeeding rates currently are the highest recorded in 30 years, although premature weaning owing to the largely avoidable problems of breast pain and concern about adequate milk supply is still common. The advantages of breastfeeding will be more widely appreciated when all health care professionals acquire competence in evidence-based lactation management strategies. These strategies include helping women to position and attach their newborns correctly, encouraging frequent and effective feedings at the breast from birth onward, teaching new parents the signs of adequate milk intake, and providing the resources for promoting breastfeeding without the competition of commercial product promotion.

Breast-fed and formula-fed infants do not differ in immunocompetent cell cytokine production despite differences in cell membrane fatty acid composition

BACKGROUND

Breast-fed and formula-fed infants differ in the amount and type of polyunsaturated fatty acids consumed. The fatty acid composition of cell membranes is related to dietary fatty acids and, in adults, changes in membrane fatty acid composition are accompanied by changes in monocyte cytokine production and hence a modification of the immunologic response.

OBJECTIVE

Our objective was to determine whether production by immunocompetent cells of the proinflammatory cytokines interleukin 1 (IL-1) and tumor necrosis factor (TNF) differs between breast-fed and formula-fed infants.

DESIGN

Twenty-six healthy infants (13 breast-fed and 13 fed modified cow-milk formula) aged 2-4 mo were studied. The fatty acid composition of red blood cell (RBC) membrane phospholipids was measured by gas-liquid chromatography and IL-1 and TNF release were measured in whole blood culture in bacterial-endotoxin-stimulated and unstimulated cells.

RESULTS

The infants' ages, weights, hemoglobin concentrations, and white blood cell counts did not differ significantly between groups. The percentage of n-3 fatty acids of total RBC phospholipid fatty acids was significantly higher in breast-fed than in formula-fed infants (6.31 +/- 2.5% compared with 2.98 +/- 0.97%); docosahexaenoic acid (22:6n-3) concentrations were also markedly higher in breast-fed infants (5.1 +/- 1.2% compared with 2.2 +/- 0.9%, P: < 0.001), but eicosapentaenoic acid (20:5n-3) and docosapentaenoic acid (22:5n-3) concentrations did not differ significantly between groups. The percentage of n-6 fatty acids was not significantly different between groups. The percentage of oleic acid (18:1) was higher in formula-fed than in breast-fed infants (16.2 +/- 0.7% compared with 20.6 +/- 1.1%; P: < 0.001). IL-1 and TNF release in whole blood culture did not differ significantly between groups.

CONCLUSION

The release of proinflammatory cytokines by immunocompetent cells does not differ significantly in breast-fed and formula-fed infants despite differences in cell membrane fatty acid composition.

Defective tumour necrosis factor-alpha production in mother's milk is related to cow's milk allergy in suckling infants

BACKGROUND

The precise role of leucocytes in human milk is still unresolved.

OBJECTIVE

To assist in clarifying the immune mechanisms involved in the development of CMA in suckling infants, we studied the role of immunoregulatory leucocytes and their mediators in human breast milk.

METHODS

The study population consisted of 43 lactating mothers and their infants, aged 0.25-8.0 months, followed-up prospectively from birth. Of these mothers, 27 had an infant with challenge-proven cow's milk allergy manifested with either skin (n = 23), gastrointestinal (n = 2) or skin and gastrointestinal symptoms (n = 3). Sixteen mothers with a healthy infant served as controls. We evaluated the spontaneous and mitogen-induced tumour necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) production of human milk leucocytes and isolated peripheral blood lymphocytes in vitro with a commercial ELISA kit.

RESULTS

TNFalpha production of breast milk leucocytes was significantly lower in the mothers with a cow's milk-allergic infant, whereas IFNgamma production of these cells was comparable in the two groups.

CONCLUSION

Our results suggest that in the breast milk of mothers having an infant with cow's milk allergy, the number and function of TNFalpha-producing cells is defective. This might lead to a disturbance in the development of oral tolerance and thereby to the development of CMA in suckling infants. These novel results may help in clarifying the etiopathogenesis of CMA.

Immunonutrition: the pediatric experience

The health benefits of specific nutrients in the diet are reviewed as they pertain to the pediatric population and its unique needs. Secretory immunoglobulins, lysozyme, interferon, and growth factors, among others, are known to confer immunological advantages to breast milk. Inhibition of bacterial pathogens, as well as permissive growth of a protective colonic ecoflora occur as a result of various cellular and biochemical mechanisms at play. The immunomodulatory properties of minerals such as iron, zinc, and selenium, are presented and the newly recognized protective role of vitamin A and its importance in developing countries and in conditions of compromised nutrition are discussed. The review also covers the role of arginine, glutamine, and nucleotides in adaptive responses of the developing gut and in pathologic states such as necrotizing enterocolitis, short bowel syndrome, and inflammatory bowel disease. Probiotics (specific microbial feeds with potential benefits to the host), and prebiotics (dietary components such as complex carbohydrates able to change the colonic microenvironment fostering colonization with non-enteropathogens) are areas of current interest because they offer alternatives for the management of the growing problem of multiple antibiotic resistance and overwhelming infections in the hospitalized patient.

Persistent HTLV-I infection of breast luminal epithelial cells: a role in HTLV transmission?

Human T cell leukemia viruses are predominantly transmitted from mother to child by breastfeeding. Endemic levels of HTLV infection are associated with ethnic groups that have traditionally practised long-term breastfeeding. In the course of long-term lactation, we have found that human milk contains leukocytes and epithelial cells and that mixed primary cultures of these milk cells are susceptible to HTLV-I infection in vitro. We have established and characterized an immortalized line of milk epithelial cells, HTLV-LEC, that are productively infected and transformed with HTLV-I. This is the first reported case of human cells, other than T cells, that are transformed with HTLV-I. Cultures of HTLV-LEC are distinctive because of the synthesis of an extensive extracellular matrix that appears to support in vitro morphogenesis. HTLV-I infection can be transmitted from HTLV-LEC into normal epithelial cells and leukocytes. Our results suggest that infected epithelial cells could be involved in the persistence and transmission of virus infection in HTLV-I carriers.

Sensitisation through breast milk?

The benefit of breast feeding to prevent or delay the development of food allergy in infants is somewhat controversial. Although prolonged breast feeding has widely been recommended for infants at high risk of allergy, studies concerning the composition of human milk in atopic mothers are scarce. Human breast milk is not a stabile concept. We have previously found that the cellular composition of human milk is significantly different in mothers with a food allergic infant than in those with a healthy child. The number of monocytes, lymphocytes or eosinophils, was greatly elevated whereas the number of activated macrophages was decreased in the breast milk of mothers with a severely allergic infant. The high numbers of eosinophils could easily increase the permeability of the gut thereby increasing the absorption of dietary antigens, and thus enhance the development of food allergies. Breast feeding provide many advantages to the suckling infant. However, infants developing food allergic symptoms on exclusive breast feeding may benefit from changing to formula feeding to protect adequate growth and to prevent the development of a more severe allergic symptomatology.

Dietary factors influencing levels of food antibodies and antigens in breast milk

The effect of a milk-free diet during late pregnancy and lactation, on levels of cows' milk specific antibodies and antigens in breast milk, was examined. Women with an allergic condition (defined as atopic) were randomly allocated to a milk-free diet (n = 10) or an unrestricted diet (n = 12). Twelve non-atopic women followed an unrestricted diet. A significant reduction (p < 0.001) in beta-lactoglobulin-specific immunoglobulin A and alpha-casein-specific immunoglobulin A levels was observed over the first 5 days in all groups. The mean level of beta-lactoglobulin antigens in breast milk from women who adhered strictly to the milk-free diet was significantly lower than the levels of the atopic group on the unrestricted diet (p < 0.02). The allergy incidence in the infants born in the atopic diet group was significantly lower compared with that of the atopic group on the unrestricted diet.

The microenvironment influences the pattern of bacterial translocation in formula-fed neonates

The authors previously demonstrated that neonatal rabbits fed conventional formula have a significantly greater incident of bacterial translocation than do neonatal rabbits fed breast milk. They hypothesized that exogenous bacteria in the formula and/or the microenvironment of the neonatal rabbit may contribute to the higher incidence of bacterial translocation. In the present study, the authors examined the incidence of bacterial translocation in neonatal rabbits fed pasteurized formula, unsterile formula, or breast milk while being housed in a clean or unsterile environment. The rabbits were divided into five groups. Groups I and II were fed pasteurized formula; groups III and IV were fed unsterile formula. In addition, groups I and III were housed in a clean environment, and groups II and IV were kept in an unsterile environment. The neonates in group V were fed breast milk and were kept in an unsterile environment. On the seventh day, the animals were killed, and the mesenteric lymph nodes, liver, and spleen were cultured for the presence of bacteria. Bacterial translocation occurred in 100% of group IV neonates. A clean environment (groups I and III) eliminated gram-negative bacterial translocation. A reduction (50%) in the overall incidence of bacterial translocation was obtained by pasteurizing the formula (group I v group III). Group II had significantly less gram-negative bacterial translocation than did group IV. None of the neonates in group V had translocation. The data show that a clean environment abrogates gram-negative bacterial translocation. Pasteurizing the formula significantly reduces the incidence of gram-negative bacterial translocation, and further reduces overall bacterial translocation in a clean environment. The authors hypothesize that control of the microenvironment can significantly influence the pattern of bacterial translocation in formula-fed neonates, and thus potentially reduce the incidence of gut-origin sepsis. Factors present in breast milk inhibit bacterial translocation, regardless of the microenvironment.

Breast milk protects the neonate from bacterial translocation

Clinical and experimental evidence suggests that breast milk enhances the neonatal gut barrier. Using bacterial translocation (BT) as a measure of gut barrier function, a series of experiments was designed to explore the relationship between the neonatal gut barrier and breast milk as well as the factors associated with the feeding of breast milk. Full-term newborn rabbits were assigned to one of four groups: formula-fed (group I), fed with colostrum plus formula (group II), breast-fed with breast milk (group III), and fed with colostrum plus stored breast milk (group IV). At 7 days of age, body weights were obtained, the rabbits were killed, and the mesenteric lymph nodes (MLN), liver, and spleen were quantitatively cultured for translocating bacteria. The cecum was cultured for aerobic and anaerobic enteric organisms. Distal ileal tissues were examined by light and transmission electron microscopy and compared among groups. The viability of cells in the stored, frozen breast milk was assessed by Trypan blue staining. Group I rabbits had significantly lower mean body weights compared with the other groups. The animals breast-fed breast milk had no BT to the MLN or liver and had a 9% incidence of BT to the spleen. There was no difference between BT in groups III and IV. The stored breast milk contained no viable cells. The incidence of BT to all three areas was significantly lower than in groups I and II. The animals fed with formula alone had the highest incidence of BT to the MLN (88%), liver (60%), and spleen (32%). BT in this group was significantly higher compared with groups III and IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal immunization to prevent infectious diseases in the neonate or infant

The approach of providing passive protection to young infants by immunizing pregnant women can bypass the problems of immunological immaturity in the neonate, avoid or delay active immunization of the infant in the first year of life, and prevent transmission of an infection from the mother to the neonate. Optimal vaccines for this approach should induce high immunoglobulin G antibody titers that quickly reach their maximum level after immunization and persist at protective levels for several years, thus providing passive protection in subsequent pregnancies. Specific applications of this approach include the worldwide practice of maternal immunization with tetanus toxoid vaccine and ongoing studies of maternal immunization to prevent Haemophilus influenzae type b, group B streptococcal, pneumococcal, meningococcal, and human immunodeficiency virus infection in the infant. Addressing the cultural, sociological, and legal aspects of maternal immunization will be required to ensure the success of this approach.

Identification of lymphocyte subsets in the human fallopian tube

PROBLEM

Immunohistochemical investigations for the detection of lymphocyte subsets in the human oviduct have been performed. Knowledge about local immunity especially cell-mediated immunity, in the fallopian tube has been, up to now, limited. As an essential structure for the human reproduction process, the tubal mucous membrane is exposed to a variety of antigens.

METHOD

A total number of 20 tubal biopsies obtained from fertile women during gynecological operations like tubal ligations or hysterectomy were examined by the immunoperoxidase technique. Seven specimens were obtained during the proliferative phase, ten during the secretory phase and three during a caesarean section with tubal ligations.

RESULTS

It could be established that the presence of lymphocytes in the oviductal mucous membrane is physiological. These cells can be identified by their typical immunohistochemical patterns. There were no significant differences of the type and number of lymphocytes in the mucosa within the phases of menstrual cycle. The dominant cell types in the tubal mucosa were the CD3+ and CD8+ lymphocytes.

CONCLUSIONS

It can be suggested that the lymphocytes in the tubal mucosa may involved in the process of immune tolerance, which could realize the transport of sperms and blastocysts through the oviduct under normal conditions without activation of local immune mechanisms. The lymphoid tissue of the oviduct is a specialized form of mucosal-associated lymphoid tissue (MALT).

Titres of class-specific antibodies against Shigella and Salmonella lipopolysaccharide antigens in colostrum and breast milk of Costa Rican, Swedish and Vietnamese mothers

Enzyme immunoassays (EIA) were used to estimate titres of class-specific antibodies against purified and chemically defined phenol-water-extracted lipopolysaccharide (LPS) antigens of Salmonella serogroup B (BO), Shigella dysenteriae type I, Plesiomonas shigelloides (the same O-antigen as Shigella sonnei) and Shigella flexneri Y. Titres in colostrum and breast milk of Swedish, Vietnamese and Costa Rican mothers from various socioeconomic conditions were compared. The antibodies were mainly of the IgA isotype. IgM antibodies were also present, but only very low concentrations of IgG were found. In Costa Rican mothers, the IgA antibody titres were significantly higher (P less than 0.05) in women of low and middle socioeconomical conditions than were those in mothers of high socioeconomical level. The low titres in the last group were comparable to those found in Swedish mothers. The IgA antibody titres found in Vietnamese mothers were similar to those of Costa Rican mothers from the low and middle socioeconomic conditions, being highest against S. flexneri Y LPS. The IgM antibody titres were also highest in Vietnamese mothers, immediately followed by the Costa Rican mothers of low socioeconomic conditions. The low IgM titres in the Costa Rican women of high socioeconomic level were comparable to those seen in Swedish mothers. The results suggest that, in Costa Rica and Vietnam, S. flexneri is the most prevalent Shigella sp. causing infection and that Salmonella serogroup B infections are rare in all three countries. The results also show that the antibody repertoire in colostrum and breast milk varies. Furthermore, in addition to the prevalence of a specific micro-organism in a determined geographical area, such differences may be associated mainly with exposure to certain pathogens in particular socioeconomic conditions.

High levels of anti-Campylobacter-flagellin IgA antibodies in breast milk

Several studies have shown the beneficial role of immunity against enteric Campylobacter sp. Circulating antibodies against flagellin and possibly maternal antibodies seem to protect against intestinal colonization by Campylobacter. Milk from women in Central Africa (n = 120) and in France (n = 31) were investigated for the presence of anti-flagellin antibodies. Results showed that most French and all African milk possessed anti-flagellin IgA but not IgG. The titres of anti-flagellin IgA were elevated in colostrum and decreased in later milk. Specific activities were constant during lactation, suggesting constant antigenic stimulation. The fact that IgA but not IgG are elicited against flagellin could be due to an infection limited to the mucosal surface.

Evidence for long-term memory of the mucosal immune system: milk secretory immunoglobulin A against Shigella lipopolysaccharides

Although the common mucosal immune system has generally been considered to have only short-term memory, recent data suggest that long-term memory exists for Shigella virulence plasmid antigens. Because such antigens might cross-react with environmental antigens, we investigated milk for the persistence of antibodies to the specific Shigella lipopolysaccharide (LPS) antigens. Enzyme-linked immunosorbent assays to detect secretory immunoglobulin A (sIgA) against Shigella flexneri and Shigella sonnei LPS in milk samples were developed; 15 random milk samples tested on different days correlated from one day to the next (P = 0.0001). Of 18 Mexican mothers, 18 (100%) had one or more milk samples positive for anti-S. flexneri LPS, 14 (78%) had one or more milk samples positive for anti-S. sonnei LPS, and 14 (78%) had one or more milk samples positive for both. Of 27 Houston mothers, 16 (59%) had one or more milk samples positive for anti-S. flexneri LPS, 7 (26%) had one or more milk samples positive for anti-S. sonnei LPS, and 5 (19%) had one or more milk samples positive for both. Mexican mothers were significantly more likely than Houston mothers to have at least one sample with a positive titer for anti-S. flexneri LPS (P less than 0.02) and at least one sample with a positive titer for anti-S. sonnei LPS (P less than 0.002). Although the Houston women had a lower rate of titer positivity for both Shigella species, the rate was too high to be consistent with short-lived mucosal immunity. It is unlikely that 18 of the 27 Houston women had shigellosis during or just prior to lactation. The data suggest that there exists a long-term hormonally driven memory in the secretory immune system for Shigella spp.

Detection of IL-6 in human milk and its involvement in IgA production

A large amount of interleukin-6 (IL-6) was found to be contained in human whey. The concentration of IL-6 in colostrum was significantly higher than that in serum or in milk taken 1 month after parturition. Colostrum contained many more mononuclear cells than late milk. In terms of the proportion of monocytes, T cells and B cells, however, there is no difference between colostrum and late milk. There is a significantly positive correlation between the concentration of IL-6 and the number of mononuclear cells in milk. This demonstrates that IL-6 in whey is derived in part from mononuclear cells. Stimulation of human milk mononuclear cells by Staphylococcus aureus Cowan I in the presence of anti-IL-6 antibody markedly decreased the production of IgA. This suggests that IL-6 contained in milk is closely associated with the local production of IgA in the breast.

Infant feeding effects on flow cytometric analysis of blood

Flow cytometric analysis was performed on purified mononuclear cells isolated from whole blood samples of 11 adults, 7 breast-fed (BF) infants and 11 formula-fed (FF) infants, mean ages 34.2 +/- 4.3 years, 6.3 +/- 1.3 months, and 6.2 +/- 1.2 months, respectively. Infants were receiving at least 70% of calories from formula or breast milk. Infant mononuclear cell populations contained a higher percentage of lymphocytes and a lower percentage of monocytes compared with adults. Within the lymphocyte population, infants had a higher CD4+/CD8+ ratio (T helper-inducer/T cytotoxic-suppressor), a higher percentage of CD19+ (pan B) and CD4+ cells, and a lower percentage of CD8+ and CD16+ (natural-killer) cells compared with adults. CD3+ (pan T) and CD4+ lymphocyte percentages were higher and CD19+ lymphocyte percentages were lower in FF compared with BF infants. Although sample size is small, our data indicate that diet may influence lymphocyte subset distribution during infancy when the majority of calories is derived from infant formula or human milk.

Comparison of concentration and avidity of specific antibodies to E. coli in breast milk and serum

To investigate the relationship between mucosal and systemic immunity we analysed the specific anti-Escherichia coli antibody concentration and avidity of IgA in colostrum and IgG in paired blood samples from 47 mothers giving birth to premature neonates. The avidity of each sample, expressed as an avidity index, was determined using a novel enzyme immunoassay (EIA)-based procedure, while specific antibody determinations were performed by means of conventional sandwich EIA techniques. All subjects had detectable antibody to E. coli in serum and breast milk. The median avidity index for specific IgA antibody in breast milk (3.53 M NH4SCN, range 2.77-4.90) was significantly higher (P less than 0.0001) than that for specific IgG antibody in serum (median 2.03 M NH4SCN, range 1.15-3.65). Using Spearman correlation analysis, a weak but significant association was found between the avidity of colostral IgA antibody and the avidity of systemic IgG antibody to pooled E. coli polysaccharides (rs = 0.29, P = 0.02). There was also a weak correlation between the concentrations of specific serum IgG antibody and of specific colostral IgA antibody (rs = 0.36, P = 0.006). There was no correlation between the concentration of IgA anti-E. coli antibody in colostrum and the avidity of colostral IgA antibody (rs = 0.14, P less than 0.05). Similarly, there was no correlation between the concentration and the avidity of serum IgG anti-E. coli antibody (rs = 0.23, P less than 0.05). The findings of this study suggest independent regulation of concentration and avidity of specific IgA antibody in preterm breast milk. Similar results were seen for specific IgG antibody in serum. The correlations between systemic and mucosal antibody with respect to both concentration and avidity were significant, but are relatively weak and therefore suggest that there also may be independent factors which afford differential regulation of systemic and mucosal antibody responses.