Mucosal IgA, mucosal cow's milk antibodies, serum cow's milk antibodies and gastrointestinal permeability in infants

We have studied development of the levels of IgA cow's milk (CM) antibodies in the saliva, faeces and serum of 20 term and 20 preterm infants from birth to 8 months. All infants already had IgA in their saliva during the first week of life. The levels peaked at the age of one month, thereafter decreasing in both groups; from the age of three months levels remained stable. Term infants had higher levels than preterm infants, but no differences were found between breastfed and CM-fed infants. Breastfed infants had higher levels of IgA in their faeces than did CM-fed infants; the IgA levels were similar in breast-fed term and preterm infants, being highest at birth, and decreasing thereafter. We also showed rising titers of serum IgA CM antibodies, with higher levels in infants regularly exposed to CM than in breast-fed infants. We sought associations between the magnitude of intestinal permeability to human a-lactalbumin (ALA) measured at the ages of 4-7 days and one month and the levels of IgG antibodies to CM, but no such relation was found.;     

Dietary insulin as an immunogen and tolerogen

We have shown that exposure to bovine insulin (BI) in cow's milk (CM) formula induces an insulin-specific immune response in infants. Here we studied the role of human insulin (HI) in breast milk as a modulator of the immune response to insulin. In a group of 128 children participating in the TRIGR pilot study, maternal breast milk samples were collected 3-7 days and/or 3 months after delivery. After exclusive breast-feeding, the children received either CM formula or casein hydrolysate during the first 6-8 months of life. Insulin concentration in breast milk and immunoglobulin G (IgG) antibodies to BI in plasma samples were measured by EIA. The levels of insulin in breast milk samples were higher in mothers affected by type 1 diabetes than in non-diabetic mothers (p = 0.007 and p < 0.001). The concentration of insulin in breast milk correlated inversely with the plasma levels of IgG antibodies to BI at 6 months of age in children who received CM formula (r = -0.39, p = 0.013), and at 12 months of age in all children (r = -0.25, p = 0.029). The levels of breast milk insulin were higher in the mothers of nine children who developed beta-cell autoimmunity when compared with autoantibody-negative children (p = 0.030); this holds true also when only children of diabetic mothers were included (p = 0.045). BI in CM induces higher levels of IgG to insulin in infants than does HI in breast-fed children. Instead, HI in breast milk seems to be tolerogenic and may downregulate the IgG response to dietary BI. However, our results in infants who developed beta-cell autoimmunity suggest that in this subgroup of children breast milk insulin does not promote tolerance.     

Effects of Formula Protein Level and Ratio on Infant Growth, Plasma Amino Acids and Serum Trace Elements I. Cow's Milk Formula

Abstract. The optimum level and ratios of protein to be used in cow's milk formula has recently been under discussion. Healthy term infants were fed from birth exclusively human milk or a formula that varied in protein level or whey:casein ratio: (A) 1.4 g/dl; 55:45, (B) 1.5 g/dl; 55:45, (C) 1.3 g/dl; 55:45, (D) 1.4 g/dl; 60:40, (E) 1.4 g/dl; 20:80. Infants were followed for 12 weeks and blood samples were taken at 2, 4, 8 and 12 weeks. Anthropometric indices did not show any significant differences among groups. Plasma amino acid and BUN levels of the C group were closest to the breast-fed group, while the formula with the highest protein level (B) resulted in high values for some amino acids. When comparing the formulas with 1.4 g protein/dl, the high casein group had the lowest plasma tryptophan levels. Taurine was added to all formulas at a level similar to that of breast milk; plasma taurine levels were similar for all groups. All formulas contained 0.7 mg iron and 0.7 mg zinc/dl; no differences were found among the groups in hematological indices or serum trace elements. These data show that feeding a formula with 1.3 g protein/dl and 55:45 whey: casein ratio from birth will result in growth and metabolic indices similar to those of breast-fed infants, although some plasma amino acid levels are not identical, 1990.     

Serum and Saliva Ig-levels in Infants of Non-Atopic Mothers Fed Breast Milk or Cow's Milk-based Formulas

ABSTRACT. Of twenty-five healthy, full term infants without a family history of atopic diseases, 13 were exclusively breast-fed from birth for a minimum of 3½ months (median 4½ months), whereas the remaining 12 infants were fed with cow's milk-based formulas from birth for a minimum of 4 months. In the latter group of children a significant increase in serum IgE as well as in salivary IgA was found. In infants exclusively breast-fed, no increase in serum IgE was seen until 6 months of age; at nine months of age, salivary IgA was still significantly lower than in the infants fed cow's milk-based formulas. No children developed obvious allergic diseases during the first three years of life. Thus, cow's milk proteins given to newborn children of non-atopic mothers did not seem to increase the risk of IgE-mediated diseases, maybe due to the development of "blocking" IgA-antibodies in the alimentary tract.     

Prolonged exclusive breast-feeding results in low serum concentrations of immunoglobulin G, A and M

Serum levels of IgG, IgA and IgM were measured in 198 infants at ages 2, 4, 6, 9 and 12 months. By age 9 months 30 infants were still exclusively breast-fed; their IgG and IgM levels were significantly lower than those of infants weaned early to formula (before age 3.5 months). By 12 months 6 infants were still exclusively breast-fed; their IgA levels were by then also similarly lower. There was no significant difference in the number of infections experienced by these groups of infants. After 2 months on formula feeding, the IgG and IgM levels of the infants who were exclusively breast-fed for 9 months had caught up with the levels of the infants weaned early to formula. Only at 12 months of age prealbumin levels of the exclusively breast-fed infants showed a positive correlation to IgG and IgA levels; no correlation was found between immunoglobulin levels and levels of serum iron and zinc.     

Low Colostral IgA Associated with Cow's Milk Allergy

ABSTRACT. During a nutritional study of 198 infants, seven became allergic to cow's milk. The seven infants showed acute cutaneous manifestations during cow's milk challenge tests in hospital and six had increased levels of IgE cow's milk-specific antibodies. Neither in the development of the levels of immunoglobulins G, A and M, nor in that of the cow's milk-specific antibodies of these isotypes did these seven patients differ from the remaining infants. Beta-lactoglobulin content and levels of cow's milk-, and beta-lactoglobulin-specific antibodies and of immunoglobulins A, G and M were measured in samples of colostrum and milk from the mothers of the seven infants with cow's milk allergy and from a comparison group (non-atopic mothers of non-atopic infants). The milk of the mothers whose infants became allergic to cow's milk contained less IgA through the lactation: 95% confidence intervals of the groups did not overlap. The difference was most marked in the colostrum. All other measurements were similar in the two groups. This suggests that an infant is more likely to develop cow's milk allergy if the mother's colostrum had a low total IgA content.     

Prolonged Exclusive Breast-Feeding Results in Low Serum Concentrations of Immunoglobulin G, A and M

ABSTRACT. Serum levels of IgG, IgA and IgM were measured in 198 infants at ages 2, 4, 6, 9 and 12 months. By age 9 months 30 infants were still exclusively breast-fed; their IgG and IgM levels were significantly lower than those of infants weaned early to formula (before age 3.5 months). By 12 months 6 infants were still exclusively breast-fed; their IgA levels were by then also similarly lower. There was no significant difference in the number of infections experienced by these groups of infants. After 2 months on formula feeding, the IgG and IgM levels of the infants who were exclusively breast-fed for 9 months had caught up with the levels of the infants weaned early to formula. Only at 12 months of age prealbumin levels of the exclusively breast-fed infants showed a positive correlation to IgG and IgA levels; no correlation was found between immunoglobulin levels and levels of serum iron and zinc.     

Breastfeeding stimulates total and cow's milk-specific salivary IgA in infants

Breastfeeding may increase the rate of mucosal maturation and IgA production. We sought to determine the effect of breastfeeding vs. formula-feeding on the maturation of oral mucosa by measuring the salivary total antibodies and cow's milk protein-specific IgA. Fifty-eight saliva samples were collected from 39 healthy, full term infants. At the age of 3 months (n = 25) eight infants received only breast milk and seventeen formula (cow's milk based n = 10, hydrolysed n = 7) and breast milk; and at the age of 6 months (n = 33) eleven received breast milk, seventeen formula and breast milk and five were not breastfed any more (cow's milk based n = 14, hydrolysed n = 8). Total IgA, IgG, IgM and protein, and β-lactoglobulin specific IgA were measured from saliva with enzyme-linked immunoassay (ELISA). The antibody results were proportioned to total protein. No differences in antibody levels between the feeding groups were found at 3 months of age. At 6 months, total IgA, total IgM and β-lactoglobulin-specific IgA were higher among the breastfed infants compared to those receiving formula as supplement to breast milk or not breastfed any more (breast milk vs. any formula p = 0.029, p = 0.015, p = 0.058; breast milk vs. cow's milk formula p = 0.025, p = 0.044, p = 0.038). To conclude, breastfeeding stimulated the mucosal immune system to produce IgA to saliva, which is a marker for immunological maturation and likely provides protection against environmental antigens.     

A Prospective Study of Cow's Milk Allergy in Exclusively Breast-Fed Infants

ABSTRACT. A cohort of 1749 newborns in the municipality of Odense were followed prospectively for the development of cow's milk allergy (CMA) during their first year of life. Altogether 39 fulfilled the criteria for CMA (2.2%). Out of the 39 infants, 17 developed symptoms of CMA during breast-feeding, in all cases before the age of 3 months. Nine of these were solely breast-fed at the time of diagnosis, giving a one year incidence of CMA in exclusively breastfed infants of 0.5% (9/1 749) in a study population with a frequency of exclusive breast-feeding of 52% at 3 months of age. None of the infants had signs of CMA in the neonatal period. Review of records from the newborn nursery revealed that all 9 infants had been exposed to cow's milk formula in amounts corresponding to approximately 0.4-3.0 g of Beta-lactoglobulin (BLG) during the first three days of life. Human milk samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for the content of bovine BLG. Detectable amounts (0.5–45 ng/ml) were found in 3/9 samples of human milk against which the infants reacted clinically. Analysis of the size distribution by high pressure liquid gel permeation chromatography in combination with ELISA indicated a molecular weight of BLG corresponding to that of monomeric BLG (18 kD). Possibly early inadvertent and occasional exposure to cow's milk proteins may initiate sensitization in predisposed neonates. Subsequent exposure to minute amounts of bovine milk proteins in human milk may act as booster doses eliciting allergic reactions.     

Cow's milk and ovalbumin-specific IgG and IgA in children with eczema: low β-lactoglobulin-specific IgG4 levels are associated with cow's milk allergy

To cite this article: Savilahti EM, Viljanen M, Kuitunen M, Savilahti E. Cow's milk and ovalbumin-specific IgG and IgA in children with eczema: low β-lactoglobulin-specific IgG4 levels are associated with cow's milk allergy. Pediatric Allergy Immunology 2012: 23: 590-596. ABSTRACT: Tolerance to allergens may partly depend on allergen-specific IgG and IgG subclasses and IgA antibodies. We investigated whether specific IgG and IgG subclasses and IgA antibodies to β-lactoglobulin, α-casein, and ovalbumin differed between infants who had verified cow's milk allergy (CMA) and infants with cow's milk (CM)-associated eczema, but negative CM oral challenge. The study population comprised 95 infants with clinical eczema that was by history associated with the consumption of CM. After an elimination period, a double-blind, placebo-controlled (DBPC) CM oral challenge confirmed CMA in 45 infants. Skin prick tests (SPT) were performed with CM and hen's egg. Serum levels of IgE antibodies to CM and hen's egg were measured with UniCAP (Phadia, Uppsala, Sweden), and levels of IgA, IgG, IgG1, and IgG4 antibodies to β-lactoglobulin, α-casein, and ovalbumin were measured with enzyme-linked immunosorbent assay. We observed that infants with CMA had lower IgG4 levels to β-lactoglobulin than infants with negative DBPC CM challenge (p?=?0.004). Positive CM SPT was associated with lower IgG4 levels to α-casein (p?=?0.04). The relation of CM IgE to β-lactoglobulin and α-casein IgG4 was higher in CMA than in infants with negative challenge (p?相似文献   

Cow's milk challenge through human milk evokes immune responses in infants with cow's milk allergy.

OBJECTIVES: In order to measure the immune response evoked in breast-fed infants with cow's milk allergy (CMA) by cow's milk challenge through human milk, mothers were given increasing doses of cow's milk after they had been on a cow's milk elimination diet. Another objective was to study the secretion of beta-lactoglobulin (BLG) into human milk before and during milk challenge in relation to the appearance of symptoms in infants. STUDY DESIGN: Seventeen asymptomatic mothers who had infants with challenge-proven CMA and 10 asymptomatic mothers who had healthy infants were recruited. Infants ranged in age from 1.8 to 9.4 months. A solid-phase enzyme-linked immunoassay (ELISPOT) was used to assess the total number of immunoglobulin-secreting and specific antibody-secreting cells. Flow cytometry was used to enumerate different lymphocyte subpopulations among peripheral blood lymphocytes primed during provocation by cow's milk antigens. BLG levels were assessed in human milk before the challenge and 1, 2, 3, and 4 hours after the commencement of the challenge. RESULTS: All but one of the infants with CMA showed symptoms of CMA during cow's milk challenge through human milk. There was a significant rise in the total number of immunoglobulin-secreting cells in the IgA and IgG classes associated with a positive cow's milk challenge response, but the proportions of peripheral blood B cells bearing CD19, CD23, CD19 and 23, CD5, or CD19 and CD5 were comparable. BLG levels were comparable in both study groups. CONCLUSIONS: Most of the infants with CMA reacted to cow's milk challenge through human milk. Hypersensitivity reactions to food antigens through human milk may be more common than previously thought.     

Does low IgA in human milk predispose the infant to development of cow's milk allergy?

We sought a relationship between total and cow's milk-specific IgA levels in colostrum and human milk and subsequent development of cow's milk allergy (CMA) in the breast-fed infant. The study included 87 nursing mothers and their infants (age, 2 d to 7 mo), followed prospectively up to 1 y. At 1 y, 48 mothers (69% with an atopic constitution) had an infant with CMA, verified by clinical cow's milk challenge, eight (38% with an atopic constitution) had a baby who had had protracted infantile colic but no CMA (disease control group), and 31 (23% with an atopic constitution) had a healthy infant. Total breast-milk IgA was measured by radial immunodiffusion, and IgA antibodies to cow's milk were measured by ELISA during the breast-feeding period. The levels of total and cow's milk-specific IgA antibodies in colostrum and human milk were significantly lower in the mothers whose baby later developed CMA [estimated third day value, 0.38 g/L (95% confidence interval, 0. 24-0.82)] than in the ones whose infant remained healthy or had had infantile colic but not CMA [0.82 g/L (95% confidence interval, 0. 99-1.51); p < 0.05]. The infants developed CMA significantly more often if the concentration of total IgA antibodies in milk was <0.25 g/L, when measured between 6 d and 4 wk postpartum [sensitivity, 0. 55; specificity, 0.92; odds ratio, 14.7 (95% confidence interval, 3. 1-70.2); p < 0.001]. The levels of cow's milk-specific IgA positively correlated with the levels of total IgA but not with the development of CMA in the infant. The levels of total or cow's milk-specific IgA did not correlate with maternal atopy. IgA antibodies in colostrum and human milk may prevent antigen entry at the intestinal surface of the breast-fed infant. A low IgA content in human milk may lead to defective exclusion of food antigens and thus predispose an offspring to develop food allergies.     

Food Intake and Growth of Infants between Six and Twenty-six Weeks of Age on Breast Milk, Cow's Milk Formula, or Soy Formula

ABSTRACT. In 59 normal infants attending well-baby clinics, food consumption was registered until 26 and growth until 52 weeks of age. They were either breast-fed or formula-fed with a cow's milk product or a soy protein product. The average consumption of breastmilk was 746, 796, 722 and 689 g/day at 6, 14, 22 and 26 weeks respectively. Bottle-fed infants received larger volumes, and at 6 and 14 weeks were the calculated total energy intakes significantly higher than in breast-fed infants. No differences were seen between the feeding groups with respect to length and the sum of four skin folds. The soy formula-fed children, who happened to be 200 g heavier at birth, had lower weight gains during the first 6 weeks than the other two groups. Thereafter, the average weights of the soy formula group did not differ from the other groups. At 3 months, the soy formula-fed children displayed a slower mineralisation and maturation of bone, but the difference was no longer significant when re-examined at 6 months. Formulas based on soy protein isolates seem to be acceptable as substitutes for cow's milk formulas in feeding normal infants.     

Effects of formula protein level and ratio on infant growth, plasma amino acids and serum trace elements. I. Cow's milk formula

The optimum level and ratios of protein to be used in cow's milk formula has recently been under discussion. Healthy term infants were fed from birth exclusively human milk or a formula that varied in protein level or whey: casein ratio: (A) 1.4 g/dl; 55:45, (B) 1.5 g/dl; 55:45, (C) 1.3 g/dl; 55:45, (D) 1.4 g/dl; 60:40, (E) 1.4 g/dl; 20:80. Infants were followed for 12 weeks and blood samples were taken at 2, 4, 8 and 12 weeks. Anthropometric indices did not show any significant differences among groups. Plasma amino acid and BUN levels of the C group were closest to the breast-fed group, while the formula with the highest protein level (B) resulted in high values for some amino acids. When comparing the formulas with 1.4 g protein/dl, the high casein group had the lowest plasma tryptophan levels. Taurine was added to all formulas at a level similar to that of breast milk; plasma taurine levels were similar for all groups. All formulas contained 0.7 mg iron and 0.7 mg zinc/dl; no differences were found among the groups in hematological indices or serum trace elements. These data show that feeding a formula with 1.3 g protein/dl and 55:45 whey: casein ratio from birth will result in growth and metabolic indices similar to those of breast-fed infants, although some plasma amino acid levels are not identical, 1990.     

Milk versus no milk in rapid refeeding after acute gastroenteritis

Sixty-five infants (mean age 14.7 months, range 6-34 months), hospitalized for acute gastroenteritis, were treated with oral rehydration and rapid reintroduction of full feedings appropriate for age. Cow's milk and milk products were eliminated from the diet of 27 infants, whereas the remaining 38 children continued to receive their usual milk and milk products as parts of the mixed diet. There was no difference between the groups in the clinical recovery from diarrhea. No child had prolonged diarrhea. No new cases of clinical atopy were observed at 1-month follow-up, and there were no significant increases in the total or milk-specific IgE levels. Serum IgG and IgA antibodies to beta-lactoglobulin and alpha-casein were initially present in the majority of the children, but there were no appreciable changes in these cow's milk antibodies after gastroenteritis, regardless of the type of diet. It is concluded that cow's milk and milk products can be safely given in acute gastroenteritis as parts of the mixed diet for children over 6 months of age. Rapid reintroduction of feedings is beneficial for recovery from diarrhea, and there appears to be little need for dietary restrictions in this age group.     

Development of immunoglobulin G and immunoglobulin E antibodies to cow's milk proteins and ovalbumin after a temporary neonatal exposure to hydrolyzed and whole cow's milk proteins

The ingestion of food antigens usually results in the induction of oral tolerance, but the clinical and immunologic consequences of brief exposure to cow's milk proteins during the neonatal period are not well‐documented. The aim of this work was to study immunoglobulin (Ig)E and IgG responses to cow's milk proteins and ovalbumin after exposure during the first three days of life in infants who were otherwise exclusively breast‐fed. A group of 129 infants was randomly assigned at birth to one of three feeding regimens: human milk (HM), cow's milk formula (CMF), or a casein hydrolysate formula (CHF), during the first three days of life. They were then all exclusively breast‐fed for a varying period of time and followed for two years. Serum IgG and IgE antibodies to cow's milk proteins and ovalbumin (OVA) were analyzed in blood samples obtained at birth, at 4 days and at 2, 4, 8, 12 and 24 months of age. The levels of IgG antibodies to β‐lactoglobulin (IgG‐BLG) and bovine serum albumin (IgG‐BSA) were higher in the CMF and the HM groups than in the CHF group for up to two years. This was particularly obvious for IgG‐BLG in infants who started weaning before two months. The levels of IgG antibodies to casein (IgG‐CAS) were higher in the CMF goup, as compared with the CHF group at 8 and 12 months. The levels of IgG antibodies to OVA were similar in all three feeding groups. The levels of IgE antibodies to CAS or OVA were similar in the three feeding groups. Exposure to cow's milk during the first three days of life stimulated IgG antibody production to cow's milk proteins and this was still obvious at 2 years of age, while feeding with a casein hydrolysate during the first three days of life was associated with low levels of IgG antibodies to cow's milk proteins.     

Response to RIT 4237 Oral Rotavirus Vaccine in Human Milk, Adapted- and Soy-Formula Fed Infants

ABSTRACT. During the first month of life 28 full-term newborns were breast-fed (18 males and 11 females). Thereafter 8 infants continued breast-feeding while the remainder were randomly fed on either an adapted milk formula ( n =13) or a soy-formula ( n =7). At five months, after an oral dose of RIT 4237 rotavirus vaccine of bovine origin was given, growth and IgM/IgG type antibodies against rotavirus were measured. Weight gain was similar in all infants. There were 2 IgM and 1 IgG responders out of 7 soy fed infants, compared with 4 out of 8 human milk fed (both IgM and IgG) and 7 out of 13 IgM and 6/12 IgG formula fed infants responding to vaccination. This observation confirms previous results obtained with polio, diphtheria tetanus and pertussis vaccines indicating that soy-protein formulas may interfere with immunization processes.     

IgA antibodies, TGF-beta1 and -beta2, and soluble CD14 in the colostrum and development of atopy by age 4

Specific defense factors in breast milk together with length of breast-feeding and genetic predisposition may modulate the development of allergy. We studied whether IgA, soluble CD14 (sCD14), or transforming growth factor (TGF)-beta in colostrum could affect the development of atopy in children up to age 4. From a cohort of 4676, we selected four groups of children with either long or short exclusive breast-feeding (>3.5 or <0.5 mo); these groups further differed in the presence or absence of atopic heredity. In colostrum from mothers, we measured total IgA, IgA antibodies to cow's milk (CM) and casein, sCD14, and TGF-beta1 and -beta2. The children were divided into three groups: those with no atopic symptoms or IgE, those with allergic symptoms, and those with both outcomes. Mothers of infants later showing atopic symptoms or, in addition, having IgE sensitization (verified atopy) had a lower concentration of IgA casein antibodies in their colostrum than did mothers of infants with no indication of atopy at age 4. Low concentration of IgA casein antibodies was a significant risk for verified atopy. sCD14 levels were lower in colostrum of mothers with infants developing atopic symptoms and IgE sensitization than of those of infants with no atopy. Specific IgA antibodies to CM antigens and sCD14 in colostrum significantly associated with the appearance of both symptomatic and verified atopy by age 4.     

Maternal consumption of dairy products during pregnancy and lactation, and the development of cow's milk antibodies in the offspring

OBJECTIVE: To assess whether the maternal consumption of milk and milk products affects development of cow's milk (CM) antibodies in infants. DESIGN: A randomized pilot trial using food frequency questionnaires (mothers) and food records (infants). SETTING: Families with a newborn infant with increased HLA-DQB1-conferred risk of type 1 diabetes and at least one first-degree relative affected by type 1 diabetes from 16 hospitals in Finland between April 1995 and November 1997. Subjects and intervention: Infants randomized to receive a hydrolysed formula when breast milk was not available during their first 6-8 mo (n=112). Of these, 13 dropped out by the age of 3 mo and two were excluded due to incomplete CM antibody data. RESULTS: Maternal milk protein intake from cheese during pregnancy was inversely related to IgA-class antibody titres to beta-lactoglobulin (BLG) and casein (CAS) at 3 mo, and to IgA antibody titres to BLG at 6 mo. Maternal consumption of raw milk products during lactation was positively related to the development of IgA antibody titres to CAS at 6 mo, and inversely correlated to IgG antibody titres to bovine serum albumin (BSA) and IgA antibody titres to CAS at 2 y. Maternal cheese consumption was inversely related to the IgG antibody titres to CM formula and CAS and to the IgA antibody titres to CAS in early infancy. CONCLUSIONS: Few associations were established between maternal CM protein intake and CM protein antibody levels in the infants. The milk and milk products taken by the mother differed in their impact on the emerging CM antibody response in the offspring.     

Breast Milk Anti-Escherichia coli Heat-Labile Toxin IgA Antibodies Protect against Toxin-Induced Infantile Diarrhea

ABSTRACT. A prospective study to assess whether milk IgA antibodies against Escherichia coli heat labile-toxin protect breast-fed children against labile toxin-induced gastroenteritis was carried out among infants of a marginal urban area in Guatemala. One hundred and thirty children were kept under surveillance for diarrhea by periodic home visits. Stool specimens were collected from each child routinely every 2-3 weeks and during diarrheal episodes, to study the excretion of labile toxin-producing Escherichia coli. Milk samples from the children's mothers were obtained concomitantly with the fecal specimens of the infants to be analyzed for anti-labile toxin antibodies. Twenty infections by heat-labile toxin-producing Escherichia coli as a sole agent were documented among breast-fed infants. Nine of these infections resulted in gastroenteritis, while the remaining 11 were asymptomatic. At the time of infection children who became sick were ingesting breast milk with significantly ( p =0.028) lower titers of antilabile toxin IgA than those who remained healthy. Only one of the 8 infected children receiving breast milk with high titers (≥256) of anti labile toxin IgA developed diarrhea, compared to 8 of the 12 subjects being fed milk with low titers (≤64) ( p =0.025). This is the first report documenting protection by IgA antibodies in milk against labile toxin-induced gastroenteritis in infected breast-fed infants.