Changes in humoral responses to beta-lactoglobulin in tolerant patients suggest a particular role for IgG4 in delayed, non-IgE-mediated cow's milk allergy

Cow's milk-induced gastrointestinal disorders: From infancy to adulthood

Milk is related to many gastrointestinal disorders from the cradle to the grave due to the many milk ingredients that can trigger gastrointestinal discomfort and disorders. Cow's milk protein allergy (CMPA) is the most common food allergy, especially in infancy and childhood, which may persist into adulthood. There are three main types of CMPA; immunoglobulin E (IgE)-mediated CMPA, non-IgE-mediated CMPA, and mixed type. CMPA appears before the first birthday in almost all cases. Symptoms may start even during the neonatal period and can be severe enough to simulate neonatal sepsis. CMPA (often non-IgE mediated) can present with symptoms of gastroesophageal reflux, eosinophilic esophagitis, hemorrhagic gastritis, food protein-induced protein-losing enteropathy, and food protein-induced enterocolitis syndrome. Most CMPAs are benign and outgrown during childhood. CMPA is not as common in adults as in children, but when present, it is usually severe with a protracted course. Lactose intolerance is a prevalent condition characterized by the development of many symptoms related to the consumption of foods containing lactose. Lactose intolerance has four typical types: Developmental, congenital, primary, and secondary. Lactose intolerance and CMPA may be the underlying pathophysiologic mechanisms for many functional gastrointestinal disorders in children and adults. They are also common in inflammatory bowel diseases. Milk consumption may have preventive or promoter effects on cancer development. Milk may also become a source of microbial infection in humans, causing a wide array of diseases, and may help increase the prevalence of antimicrobial resistance. This editorial summarizes the common milk-related disorders and their symptoms from childhood to adulthood.

The epithelial barrier and immunoglobulin A system in allergy

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

Food IgG4 antibodies are elevated not only in children with wheat allergy but also in children with gastrointestinal diseases

BACKGROUND

Food sIgG and sIgG4 are highly individually versatile. We put a hypothesis that one of the responsible factors is the presence of gastrointestinal inflammatory diseases. The objectives were: 1. An analysis of wheat and rice sIgG and sIgG4 in healthy children, children with IgE-mediated wheat allergy (WA), coeliac disease (CD) and Helicobacter pylori infection (HP). 2. Usability of wheat sIgG and sIgG4 in the WA diagnostics.

METHODS

We compared 388 each wheat and rice sIgG and sIgG4 in a group of 200 children: 50 WA (diagnosis, diet treatment, tolerance), 50 CD (diagnosis and remission), 50 HP and 50 healthy. SIgE, sIgG, sIgG4 were determined with the FEIA method (Pharmacia CAP System).

RESULTS

In healthy children food sIgG were the lowest; no sIgG4 were found. In the CD diagnosis group wheat and rice sIgG and rice sIgG4 were the most common and their concentrations were the highest (p < .001, p < .05). Wheat sIgG4 were the highest in WA children (diagnosis and tolerance) to fall during the elimination diet (p < .05). Wheat and rice sIgG remained the same in all allergy phases. Rice sIgG also did not differ in the class G4.

CONCLUSIONS

1. Serum concentrations of wheat and rice sIgG and sIgG4 are elevated in children with CD, HP and WA. 2. Sub-clinical incidence of some gastrointestinal inflammatory diseases may be responsible for high individual versatility of food sIgG and sIgG4 concentrations in serum. 3. Wheat sIgG and sIgG4 in children do not correlate with WA clinical picture.

Markers of gut mucosal inflammation and cow's milk specific immunoglobulins in non-IgE cow's milk allergy

Background

Allergy to cow’s milk protein (CMP) may cause gastrointestinal (GI) symptoms in the absence of CMP specific IgE. The immunological mechanisms involved in such disease are not fully understood. Therefore we examined markers of gut mucosal inflammation and the immunoglobulin profiles in children with Gl symptoms suspected of cow’s milk protein allergy (CMPA).

Patients and methods

We prospectively recruited infants and young children (n = 57; median age 8.7 months) with gastrointestinal complaints suspected of CMPA. The diagnosis of CMPA was made using the double-blind, placebo-controlled food challenge. Serum and stool samples were collected during CMP-free diet and after both placebo and active challenges. We analyzed the stool samples for calprotectin, human β-defensin 2 and IgA. In serum, we analyzed the levels of β-lactoglobulin and α-casein specific IgA, and IgG antibodies (total IgG and subclasses IgG1 and IgG4). Control group included children with e.g. dermatological or pulmonary problems, consuming normal diets.

Results

Fecal calprotectin levels were higher in the challenge positive group (n = 18) than in the negative (n = 37), with respective geometric means 55 μg/g [95% confidence interval 38–81] and 29 [24–36] μg/g (p = 0.0039), during cow’s milk free diet. There were no significant inter-group differences in the fecal β-defensin and IgA levels. The CMP specific IgG and IgA were not elevated in patients with CMPA, but the levels of β-lactoglobulin-IgG4 (p = 0.0118) and α-casein-IgG4 (p = 0.0044), and total α-casein-IgG (p = 0.0054) and -IgA (p = 0.0050) in all patient samples (regardless of CMPA diagnosis) were significantly lower compared to the control group using dairy products.

Conclusions

Despite cow’s milk elimination in children intolerant to cow’s milk there might be ongoing low-grade inflammation in the gut mucosa. CMP specific IgG or IgA should not be used to diagnose non-IgE CMPA. The observed frequency of impaired CMP specific total IgA, IgG and IgG4 production in patients following cow’s milk free diet warrants further studies.

Egg-white-specific IgA and IgA2 antibodies in egg-allergic children: is there a role in tolerance induction?

BACKGROUND

Decreased serum food-specific IgA antibodies have been associated with allergic disease in cross-sectional, case-control studies. The purpose of this study was to prospectively compare egg-white-(EW)-specific IgA and IgA2 levels between egg-allergic children and children tolerating egg.

METHODS

Seventeen egg-allergic children were followed prospectively. Total IgA, EW-specific IgA, and EW-specific IgA2 levels were measured in their sera with a sensitive ELISA. As negative controls were used children with no previous history of egg allergy. Egg-allergic children with or without concomitant milk allergy were evaluated as additional controls with measurement of casein-specific IgA.

RESULTS

After 2.5 ± 0.9 yrs, nine out of the 17 allergic children became tolerant and eight remained allergic to baked egg. Baseline EW-specific IgA2 levels were significantly lower in the egg-allergic subjects (median 23.9 ng/ml) compared with the negative control subjects (99.4 ng/ml) and increased significantly by 28% over the study time period in eight out of the nine allergic children that became tolerant to baked egg. There was no significant change over time in EW-specific IgA in any of the study groups. Non-milk-allergic subjects with concomitant egg allergy had almost threefold higher casein-specific IgA levels than the milk- and egg-allergic subjects (p = 0.025).

CONCLUSIONS

These results suggest a potential role for allergen-specific IgA2 antibodies in the induction of food tolerance. Furthermore, they support the hypothesis that immature or impaired production of allergen-specific IgA2 may be associated with the pathophysiology of food allergy, a defect that seems to be selective for the culprit allergen.

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

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 < 0.002 and 0.0001). Positive egg SPT was associated with elevated levels of specific IgG to ovalbumin, β-lactoglobulin, and α-casein as well as IgA to α-casein (p < 0.04). Our study thus shows that low β-lactoglobulin-specific serum IgG4 levels may differentiate eczematous infants with CMA from infants who have eczema with only suspected association with CM.

Characteristics of patients suffering from cow milk allergy

The most frequent symptoms among the manifestations of cow milk allergy (CMA) are gastrointestinal. CMA pathogenesis involves immunological mechanisms with participation of immunocompetent cells, production of immunoglobulin E (IgE) and immunoglobulin G (IgG). We aim to determine whether cow milk-specific IgE antibodies coexist with cow milk-specific IgG antibodies in CMA patients with diarrhea symptom, and if there is any relationship between both antibody types. 65 CMA patients (average age of 17 years, ranging from 2 to 74 years), all of who had diarrhea symptom of CMA, were enrolled in this study. The total cow IgE and IgG subclass in serum were measured by electrochemiluminescence immunoassay and rate immune scatter turbidimetry, respectively. And also the cow milk-specific IgE was determined by enzyme-linked immunosorbent assay. The number of eosinophils in serum was calculated by Sysmex XE-2100 Hematology Analyzer. Our data showed that both cow milk-specific IgG and IgE levels were significantly elevated in CMA patients compared to those of age-matched control subjects. Out of the 65 CMA patients, 40 showed elevated cow milk-specific IgE antibody level, among which, 28 cases presented highly sensitive reaction to cow milk-specific IgG, along with each six of moderate and mild sensitive reaction to cow milk-specific IgG; while 20 showed elevated total IgG levels. The IgG3 positive rate was 16.9%, which was the highest. A moderate correlation between cow milk-specific IgE and cow milk-specific IgG was found in the CMA patients (r=0.415, P=0.001). The results indicated that cow milk-specific IgE antibodies could coexist with cow milk-specific IgG antibodies in patients suffering from CMA. The aberrant changes in the concentration of cow milk-specific IgE antibodies were associated with cow milk-specific IgG antibodies.

A novel, high-sensitivity and drug-tolerant sandwich immunoassay for the quantitative measurement of circulating proteins

Background: Accurate measurement of a total protein target (free plus bound) is essential to optimize dose selection for monoclonal antibody drugs. Herein, we describe a novel sandwich immunoassay format in which the biotherapeutic antibody itself serves as the primary detection antibody. A signal is then generated through the addition of a labeled secondary antibody that recognizes the biotherapeutic antibody. The secondary antibody is conjugated with ruthenium to facilitate electrochemiluminescent analysis. Results: Data are presented from the analysis of two protein biomarkers having disparate size and structure; a 4.5 kDa peptide and a 60 kDa protein. In both cases, validated, highly specific assays were developed and shown to be tolerant to elevated levels of the therapeutic monoclonal antibody in question. Conclusion: Our novel format allows drug-tolerant measurement of soluble protein biomarkers targeted by monoclonal antibodies when only two independent epitopes for antibody binding are available and one is recognized by the therapeutic antibody.

Patients suffering from non-IgE-mediated cow's milk protein intolerance cannot be diagnosed based on IgG subclass or IgA responses to milk allergens

BACKGROUND

Cow's milk is one of the most common causes of food allergy. In two-thirds of patients, adverse symptoms following milk ingestion are caused by IgE-mediated allergic reactions, whereas for one-third, the mechanisms are unknown. Aim of this study was to investigate whether patients suffering from non-IgE-mediated cow's milk protein intolerance can be distinguished from persons without cow's milk protein intolerance based on serological measurement of IgG and IgA specific for purified cow's milk antigens.

METHODS

We determined IgG(1-4) subclass and IgA antibody levels to purified recombinant αS1-casein, αS2-casein, β-casein, κ-casein, α-lactalbumin, and β-lactoglobulin in four patient groups by ELISA: Patients with IgE-mediated cow's milk allergy (CMA, n=25), patients with non-IgE-mediated cow's milk protein intolerance (CMPI, n=19), patients with gastrointestinal symptoms not associated with cow's milk ingestion (GI, n=15) and control persons without gastrointestinal problems (C, n=26). Cow's milk-specific IgE levels were determined by ImmunoCAP.

RESULTS

Only CMA patients had IgE antibodies to cow's milk. Cow's milk allergic patients mounted the highest IgG(1) and IgG(4) antibody levels to αS1-casein, αS2-casein, β-casein, κ-casein, and α-lactalbumin. No elevated levels of IgG(4) , IgA, and complement-binding IgG subclasses (IgG(1) , IgG(2) , IgG(3) ) to purified cow's milk allergens were found within the CMPI patients compared to persons without cow's milk protein intolerance (GI and C groups).

CONCLUSION

Cow's milk protein intolerant patients cannot be distinguished from persons without cow's milk protein intolerance on the basis of IgG subclass or IgA reactivity to cow's milk allergens.

Predictive factors for the persistence of cow's milk allergy

Cow's milk allergy (CMA) is usually transient, but recent studies have shown a later acquisition of tolerance to CM. Our aims were to characterize a population of Portuguese children with CMA and to identify predictive factors for the persistence of this food allergy. Children with CMA observed in our Paediatric Allergy Clinic between 1997 and 2006 were selected. Demographic and clinical data were collected from medical records. The group of children who tolerated CM before the age of 2 was compared with the group of children who tolerated CM beyond that age or persisted with CMA until the end of the study. Multivariate logistic regression analysis was used to investigate independent predictive factors for the persistence of CMA beyond the age of 2. In the subgroup of children with IgE-mediated CMA, the acquisition of tolerance was analysed using Cox regression. In this population of 139 children, the majority presented more than one symptom (73%) affecting more than one organ (51%), with cutaneous (81%), gastrointestinal (55%), respiratory (16%) manifestations and/or anaphylaxis (3%). Thirty-two per cent developed asthma, 20% atopic eczema, 20% rhinoconjunctivitis and 19% other food allergies over time. The acquisition of tolerance was different in the whole population versus the subgroup with IgE-mediated CMA: 34%versus 0% at the age of 2, 55%versus 22% at the age of 5 and 68%versus 43% at the age of 10. Immediate allergic symptoms, asthma and other food allergies were independent factors for the persistence of CMA beyond the age of 2. Higher maximum weal diameter on skin prick test to CM and higher maximum level of specific IgE to CM were associated with reduced likelihood of acquiring tolerance in the subgroup of children with IgE-mediated CMA. In conclusion, children with IgE-mediated CMA acquire tolerance to CM at older age. Clinical parameters and allergy tests may be helpful in defining prognosis. CM-allergic children tend to develop other atopic conditions and need specialized follow-up in the long term.

Milk protein IgG and IgA: The association with milk-induced gastrointestinal symptoms in adults

AIM: To study the association between serum levels of milk protein IgG and IgA antibodies and milk-related gastrointestinal symptoms in adults.

METHODS: Milk protein IgG and IgA antibodies were determined in serum samples of 400 subjects from five outpatient clinics in Southern Finland. Subjects were randomly selected from a total of 1900 adults undergoing laboratory investigations in primary care. All 400 participants had completed a questionnaire on abdominal symptoms and dairy consumption while waiting for the laboratory visit. The questionnaire covered the nature and frequency of gastrointestinal problems, the provoking food items, family history and allergies. Twelve serum samples were disqualified due to insufficient amount of sera. The levels of specific milk protein IgG and IgA were measured by using the ELISA technique. The association of the milk protein-specific antibody level was studied in relation to the milk-related gastrointestinal symptoms and dairy consumption.

RESULTS: Subjects drinking milk (n = 265) had higher levels of milk protein IgG in their sera than non-milk drinkers (n = 123, P < 0.001). Subjects with gastrointestinal problems related to milk drinking (n = 119) consumed less milk but had higher milk protein IgG levels than those with no milk-related gastrointestinal symptoms (n = 198, P = 0.02). Among the symptomatic subjects, those reporting dyspeptic symptoms had lower milk protein IgG levels than non-dyspeptics (P < 0.05). However, dyspepsia was not associated with milk drinking (P = 0.5). The association of high milk protein IgG levels with constipation was close to the level of statistical significance. Diarrhea had no association with milk protein IgG level (P = 0.5). With regard to minor symptoms, flatulence and bloating (P = 0.8), were not associated with milk protein IgG level. Milk protein IgA levels did not show any association with milk drinking or abdominal symptoms. The levels of milk protein IgA and IgG declined as the age of the subjects increased (P < 0.004).

CONCLUSION: Milk protein IgG but not milk IgA seems to be associated with self-reported milk-induced gastrointestinal symptoms.

High levels of IgG4 antibodies to foods during infancy are associated with tolerance to corresponding foods later in life

Children with eczema and sensitization to foods are recommended skin care and, if food allergy is proven by challenge, an elimination diet. For most children the diet period is transient, but the process behind tolerance development and the influence of decreased allergen exposure is not fully known. The aim of the study was to investigate the effect of elimination diet on serum and salivary antibodies and to identify immunological parameters related to the ability to tolerate foods. Eighty-nine children, below 2 yr of age, with eczema and suspected food allergy were included. Recommended treatment was skin care to all children, and 60 children had a period of elimination diet. At 4(1/2) yr of age, the children were divided into two groups, based on if they had been able to introduce the eliminated foods, or not. Serum and salivary antibodies were analyzed with enzyme-linked immunosorbent assay and UniCAP before and after a 6-wk treatment period and at 4(1/2) yr of age. Children sensitized to egg and/or milk that could eat and drink the offending foods at 4(1/2) yr of age, had higher levels of Immunoglobulin G(4) antibodies to ovalbumin and beta-lactoglobulin and also higher IgG(4)/Immunoglobulin E ratios on inclusion in the study, than those who had to eliminate egg and/or milk from their diet, beyond 4(1/2) yr of age. The highest IgG(4)/IgE ratios were found in children with circulating IgE antibodies to egg and/or milk but negative skin prick test on inclusion. The 6-wk treatment period did not significantly affect the levels of serum and salivary antibodies. In conclusion, eczematous, food sensitized infants with high levels of IgG(4) and high ratios of IgG(4)/IgE antibodies to food allergens are more likely to consume these foods at 4(1/2) yr than infants with low levels and ratios.

Potential for early-life immune insult including developmental immunotoxicity in autism and autism spectrum disorders: focus on critical windows of immune vulnerability

Early-life immune insults (ELII) including xenobiotic-induced developmental immunotoxicity (DIT) are important factors in childhood and adult chronic diseases. However, prenatal and perinatal environmentally induced immune alterations have yet to be considered in depth in the context of autism and autism spectrum disorders (ASDs). Numerous factors produce early-life-induced immune dysfunction in offspring, including exposure to xenobiotics, maternal infections, and other prenatal-neonatal stressors. Early life sensitivity to ELII, including DIT, results from the heightened vulnerability of the developing immune system to disruption and the serious nature of the adverse outcomes arising after disruption of one-time immune maturational events. The resulting health risks extend beyond infectious diseases, cancer, allergy, and autoimmunity to include pathologies of the neurological, reproductive, and endocrine systems. Because these changes may include misregulation of resident inflammatory myelomonocytic cells in tissues such as the brain, they are a potential concern in cases of prenatal-neonatal brain pathologies and neurobehavioral deficits. Autism and ASDs are chronic developmental neurobehavioral disorders that are on the rise in the United States with prenatal and perinatal environmental factors suspected as contributors to this increase. Evidence for an association between environmentally associated childhood immune dysfunction and ASDs suggests that ELII and DIT may contribute to these conditions. However, it is not known if this linkage is directly associated with the brain pathologies or represents a separate (or secondary) outcome. This review considers the known features of ELII and DIT and how they may provide important clues to prenatal brain inflammation and the risk of autism and ASDs.

Fractional exhaled nitric oxide in infants during cow's milk food challenge

Cow's milk allergy (CMA) is the most common food allergy in early childhood. The golden standard for the diagnosis of CMA is a food challenge after a period of elimination. Increased levels of fractional exhaled nitric oxide (FE(NO)) have been shown after bronchial allergen provocation. We evaluated whether FE(NO) may also be a predictor of a positive reaction during cow's milk challenge in infants. Forty-four infants [mean age (range): 4.2 (3.7-4.6) months] suspected of CMA underwent an open food challenge with cow's milk formula administered in ascending quantities, starting with 2 ml and then 6, 20, 60 and 200 ml until a clinical reaction occurred. Off-line FE(NO) samples were obtained during tidal breathing by means of a facemask covering infants' nose and mouth. FE(NO) was measured twice before the challenge (baseline), immediately before each new dose of milk and after a positive reaction or after the last dose of milk. Eleven children showed immediate positive clinical responses to cow's milk, whereas 13 infants presented only a late-type reaction. FE(NO) values before or after a positive reaction (either immediate or late) were not different from FE(NO) values at baseline. Baseline FE(NO) in infants with a positive reaction did not differ from FE(NO) in infants without a reaction at any time point. We conclude that FE(NO) values are not predictive and not related to the occurrence of a positive reaction during a cow's milk challenge in infants, suggesting that a positive reaction may not result from eosinophilic activation.

Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report

Serological tests for immunoglobulin G4 (IgG4) against foods are persistently promoted for the diagnosis of food-induced hypersensitivity. Since many patients believe that their symptoms are related to food ingestion without diagnostic confirmation of a causal relationship, tests for food-specific IgG4 represent a growing market. Testing for blood IgG4 against different foods is performed with large-scale screening for hundreds of food items by enzyme-linked immunosorbent assay-type and radioallergosorbent-type assays in young children, adolescents and adults. However, many serum samples show positive IgG4 results without corresponding clinical symptoms. These findings, combined with the lack of convincing evidence for histamine-releasing properties of IgG4 in humans, and lack of any controlled studies on the diagnostic value of IgG4 testing in food allergy, do not provide any basis for the hypothesis that food-specific IgG4 should be attributed with an effector role in food hypersensitivity. In contrast to the disputed beliefs, IgG4 against foods indicates that the organism has been repeatedly exposed to food components, recognized as foreign proteins by the immune system. Its presence should not be considered as a factor which induces hypersensitivity, but rather as an indicator for immunological tolerance, linked to the activity of regulatory T cells. In conclusion, food-specific IgG4 does not indicate (imminent) food allergy or intolerance, but rather a physiological response of the immune system after exposition to food components. Therefore, testing of IgG4 to foods is considered as irrelevant for the laboratory work-up of food allergy or intolerance and should not be performed in case of food-related complaints.

Patterns of immunoglobulin G responses to egg and peanut allergens are distinct: ovalbumin-specific immunoglobulin responses are ubiquitous, but peanut-specific immunoglobulin responses are up-regulated in peanut allergy

BACKGROUND

The clinical significance of food-specific IgG subclasses in food allergy and tolerance remains unclear. Specific IgG titres are often reported in non-standardized units, which do not allow comparisons between studies or allergens.

OBJECTIVE

To quantify, in absolute units, ovalbumin (OVA)- and peanut-specific IgG levels in children with peanut or egg allergy (active or resolved) and in non-allergic controls. Methods Children aged 1-15 years were recruited. Peanut allergy was diagnosed by convincing history and a 95% predictive level of specific IgE; egg allergy or resolution was confirmed by oral challenge. Serum IgG, IgG1 and IgG4 levels (microg/mL) to OVA and peanut extract were quantified by ELISA.

RESULTS

OVA- and peanut-specific IgG was detected in all subjects. In non-allergic controls (n=18), OVA-specific IgG levels were significantly higher than peanut-specific IgG (median microg/mL IgG=15.9 vs. 2.2, IgG1=1.3 vs. 0.6, IgG4=7.9 vs. 0.7; P<0.01). There were no differences in OVA-specific IgG, IgG1 and IgG4 between egg-allergic (n=40), egg-resolved (n=22) and control (n=18) subjects. In contrast, peanut-specific IgG (median microg/mL IgG=17.0, IgG1=3.3, IgG4=5.2) were significantly higher in peanut-allergic subjects (n=59) compared with controls and with non-peanut-sensitized but egg-allergic subjects (n=26). Overall, the range of IgG4 was greater than IgG1, and IgG4 was the dominant subclass in >60% of all subjects.

CONCLUSION

OVA-specific IgG levels of egg-allergic, egg-resolved or control groups are not distinguishable. Higher peanut-specific IgG levels are associated with clinical allergy, but the range of IgG titres of the allergic and control groups overlapped. Hence, OVA and peanut-specific IgG measurements do not appear to be of diagnostic value. Strong IgG responses to OVA may be a normal physiological response to a protein frequently ingested from infancy, whereas up-regulated IgG responses in peanut allergy may be indicative of a dysregulated immune response to peanut allergens.

Maintenance of tolerance to cow's milk in atopic individuals is characterized by high levels of specific immunoglobulin G4

BACKGROUND

The central role of specific IgE in cow's milk allergy (CMA) is well documented. However, less is known about the function of other immunoglobulin isotypes in allergy and tolerance to cow's milk proteins (CMPs).

OBJECTIVE

To determine differences in the antibody responses that are associated with allergy and tolerance to cow's milk in allergic, atopic and non-atopic individuals of different age groups.

METHODS

Nineteen infants (<1 year), 18 children (6-14 years) and 41 adults (21-68 years) were included. Each age group was comprised of subjects with CMA, atopic individuals without a history of CMA and non-atopic subjects. Levels of specific IgE, IgG4, IgG1 and IgA to whole cow's milk and the six most abundant individual CMPs were determined in plasma by ELISA. For comparison, specific IgE and IgG4 were measured to ovomucoid and house dust mite (HDM) in individuals allergic for the respective allergens, and in atopic and non-atopic subjects without allergy.

RESULTS

In infants and children with CMA, alphas1-casein and beta-lactoglobulin induced the highest specific IgE response, whereas alphas1-casein was the most allergenic CMP in adult patients. Specific IgG4 and IgG1 responses were the highest to alphas1-casein and beta-lactoglobulin in all age groups, while kappa-casein and alpha-lactalbumin induced the highest levels of IgA. CMP-specific IgG4 was higher in atopic children and adults without CMA, as compared with non-atopic individuals. A similar difference between tolerant atopic and non-atopic subjects was observed for IgG4 specific to ovomucoid, whereas HDM-specific IgG4 was not detectable in these subjects.

CONCLUSION

Maintenance of tolerance to cow's milk in atopic children and adults without CMA is associated with elevated levels of specific IgG4, in combination with low specific IgE. The up-regulation of specific IgG4 in tolerant atopic individuals may be related to the type of allergen and its regular dose of exposure.

Casein-specific immunoglobulins in cow's milk allergic patient subgroups reveal a shift to IgA dominance in tolerant patients

Differences in casein-specific immunoglobulin (Ig) G-subclass and IgA serum levels between reactive and tolerant patients may hint at the immunopathogenesis during tolerance development in cow's milk allergy (CMA). alpha-, beta- and kappa-casein-specific IgG(1), IgG(4), IgE and IgA serum levels were compared in clinically reactive and tolerized IgE-mediated (n = 15) and non-IgE-mediated (n = 14) CMA with delayed gastrointestinal symptoms, using enzyme-linked immunosorbent assay (ELISA) and immunoblot techniques. The median anti-casein IgE levels in clinically reactive IgE-mediated CMA patients (n = 9) were 140- to 180-fold higher than in tolerized patients (n = 6) and 160- to 200-fold higher than in controls (n = 10). Median alpha-, beta- and kappa-casein-specific IgG(1) and IgG(4) levels were nine- to 60-fold higher in reactive patients and five- to 60-fold in tolerized patients. Clinical tolerance in IgE-mediated CMA was thus associated with decreased casein-specific IgE, IgG(4) and IgG(1), whereas serum IgA anti-alpha -, beta- and kappa-casein remained practically unaltered. Tolerized cow's milk protein (CMP)-sensitive atopic dermatitis had, in particular, decreased kappa-casein-specific IgG(1) levels, compared with clinically reactive patients. The ELISA levels to immunoblot correlation profile for the alpha-, beta- and kappa-casein-specific IgE suggested that the IgE-mediated CMA patients predominantly reacted to tertiary alpha- and beta-casein epitopes whereas the IgE in non-IgE-mediated patients reacted to linearized alpha-, beta- and kappa-casein epitopes. Clinical tolerance in non-IgE-mediated CMA patients (n = 9) was associated with a four- to 10-fold decrease in casein-specific IgE levels, accompanied by a five- to eightfold decrease in IgG(1) and five- to 60-fold decrease in IgG(4) levels, whereas casein-specific IgA levels remained unaltered. Thus, tolerance in both patient groups was characterized by a generalized decreased humoral immune response to caseins, which induced a functional shift to IgA dominance.