The IgE and IgG subclass antibody response to foods in babies during the first year of life and their relationship to feeding regimen and the development of food allergy

Timing of Cow's Milk or Cow's Milk Formula Introduction to the Infant Diet and Atopic Risk in Children: a Systematic Review and Meta-analysis

Infant feeding is an important early-life exposure that may influence the development of atopic disease. The optimal timing of introduction of food allergens, including cow's milk (CM), is not known. This study aims to systematically review the evidence describing the effects of timing of CM or cow's milk formula (CMF) introduction to the infant diet on the development of atopic diseases during childhood. Pubmed, Embase, CINAHL, Cochrane CENTRAL, and CNKI were searched through May 30, 2019. Study screening and data extraction by two reviewers followed the PRISMA statement. Data were extracted independently in duplicate, and meta-analyses were performed by pooling unadjusted and adjusted odds ratio (OR) separately. Heterogeneity was explored using I² and publication bias by funnel plots and Begg's tests. In total, 45 studies from 20 countries were included. Meta-analyses using adjusted data showed that no associations were observed between early introduction of CM or CMF and the risk of asthma (< 4 vs. ≥ 4 months: OR 1.16, 95% confidence interval (CI) 0.89, 1.51), wheeze (< 6 vs. ≥ 6 months: OR 1.15, 95% CI 0.85, 1.56), and eczema or atopic dermatitis (< 6 vs. ≥ 6 months: OR 0.96, 95% CI 0.65, 1.41). Overall, quite little high-quality evidence was identified to allow for definitive conclusions on the association between early CM or CMF introduction and risk of allergic diseases. Our meta-analysis on this topic highlights the specific gaps in information for public recommendations regarding CM or CMF feeding practice in an early stage of life, particularly before 3 months of age.

Specific oral tolerance induction in paediatric patients with persistent egg allergy

INTRODUCTION

Desensitisation or specific oral tolerance induction (SOTI) to food is a new topical-therapeutic approach of food allergy for those children who have not achieved tolerance spontaneously. The objective of this study is to induce clinical tolerance in children with persistent allergy using an oral desensitisation protocol with powdered pasteurised egg.

METHODS

Seventy-two patients with egg allergy confirmed by open oral challenge test were randomly assigned to SOTI or elimination diet as a control group. Forty children (5-15 years) underwent a SOTI beginning with 1mg and increasing the dosage weekly until a dose of 10g, equivalent to an egg. The control group included 32 patients (4-15 years).

RESULTS

The procedure's average duration was 10 weeks (range 4-28 weeks). Three patients were withdrawn from the protocol for persistent gastrointestinal symptoms. During SOTI, 21 children (52.5%) presented symptoms. In eight the symptoms were mild and required no treatment. In the other 13 (61.90%), the reactions were more severe. Seventeen children finished the treatment over a year ago and 20 in the past 6-12 months. Thirty-seven patients (92.5%) in the active group achieved tolerance to egg, versus 21.8% in the control group. We only found statistically significant differences (p<0.05) for skin prick tests with powdered egg at various dilutions and IgG levels with egg white after SOTI. Specific IgE concentration did not change significantly.

CONCLUSIONS

Our SOTI protocol is a safe, effective treatment for food allergy and of reasonable duration, confirming that tolerance can be induced in children who have not achieved it spontaneously.

Development of natural tolerance and induced desensitization in cow's milk allergy

Cow's milk allergy (CMA) affects 2-3% of infants. It resolves in the great majority spontaneously during childhood. CMA encompasses a spectrum of clinical and immunologic characteristics. Non-IgE-mediated allergy typically resolves earlier than IgE-mediated allergy. The most documented prognostic characteristic is that intense-specific IgE response predicts persistence of CMA. Low serum levels of cow's milk (CM)-specific IgG4 are also associated with persistent CMA. Natural development of tolerance involves an immunologic shift where Th2 responses diminish, and Th1 as well as T regulatory cell responses strengthen. Accordingly, specific IgE levels decrease and specific IgG4, possibly also IgA, levels increase in serum. Specific oral immunotherapy (OIT) with CM induces desensitization in most cases where spontaneous recovery has not yet occurred. Data on long-term tolerance induction are still scarce. According to current research data, the immunologic changes induced by OIT resemble those seen during natural development of tolerance.

A specific mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides induces a beneficial immunoglobulin profile in infants at high risk for allergy

BACKGROUND

It has been suggested that human breast milk oligosaccharides play a role in the development of the immune system in infants, and may consequently inhibit the onset of allergy. A specific prebiotic mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides (GOS/FOS) has been shown to reduce the incidence of atopic dermatitis (AD) at 6 months of age in infants at risk for allergy.

AIM OF THE STUDY

This study was aimed to analyze the effect of GOS/FOS on the immune response in these infants.

METHODS

In a double-blind randomized placebo-controlled study, infants received a hypoallergenic whey formula with either 8 g/l GOS/FOS in a 9 : 1 ratio (IMMUNOFORTIS) or 8 g/l maltodextrine (placebo) for 6 months. At 3 months of age, children were vaccinated with Hexavac against a.o. diphteria, tetanus, polio (DTP). At 6 months of age, plasma samples were collected from 84 infants (verum group n = 41, placebo group n = 43). Levels of total immunoglobulins (Ig) and of cow's milk protein (CMP-) and DTP-specific Ig were measured.

RESULTS

GOS/FOS supplementation led to a significant reduction in the plasma level of total IgE, IgG1, IgG2 and IgG3, whereas no effect on IgG4 was observed. CMP-specific IgG1 was significantly decreased. DTP-specific Ig levels were not affected.

CONCLUSIONS

This study shows that GOS/FOS supplementation induces a beneficial antibody profile. GOS/FOS reduces the total Ig response and modulates the immune response towards CMP, while leaving the response to vaccination intact. This suggests that oral GOS/FOS supplementation is a safe method to restrain the atopic march.

Development of antigen-specific ELISA for circulating autoantibodies to extracellular matrix protein 1 in lichen sclerosus

Lichen sclerosus is a common, acquired chronic inflammatory skin disease of unknown etiology, although circulating autoantibodies to the glycoprotein extracellular matrix protein 1 (ECM1) have been detected in most patients' sera. We have examined the nature of ECM1 epitopes in lichen sclerosus sera, developed an ELISA system for serologic diagnosis, and assessed clinicopathological correlation between ELISA titer and disease. Epitope-mapping studies revealed that lichen sclerosus sera most frequently recognized the distal second tandem repeat domain and carboxyl-terminus of ECM1. We analyzed serum autoantibody reactivity against this immunodominant epitope in 413 individuals (95 subjects with lichen sclerosus, 161 normal control subjects, and 157 subjects with other autoimmune basement membrane or sclerosing diseases). The ELISA assay was highly sensitive; 76 of 95 lichen sclerosus patients (80.0%) exhibited IgG reactivity. It was also highly specific (93.7%) in discriminating between lichen sclerosus and other disease/control sera. Higher anti-ECM1 titers also correlated with more longstanding and refractory disease and cases complicated by squamous cell carcinoma. Furthermore, passive transfer of affinity-purified patient IgG reproduced some histologic and immunopathologic features of lichen sclerosus skin. This new ELISA is valuable for the accurate detection and quantification of anti-ECM1 autoantibodies. Moreover, the values may have clinical significance in patients with lichen sclerosus.

The effects of exclusion of dietary egg and milk in the management of asthmatic children: a pilot study

Current understanding of the use of exclusion diets in the management of asthma in children is limited and controversial. The aim of this study was to examine the effects of excluding eggs and milk on the occurrence of symptoms in children with asthma and involved 22 children aged between three and 14 years clinically diagnosed as having mild to moderate disease. The investigation was single blind and prospective, and parents were given the option of volunteering to join the 'experiment' group, avoiding eggs, milk and their products for eight weeks, or the 'control' group, who consumed their customary food. Thirteen children were recruited to the experimental group and nine to the control group. A trained paediatrician at the beginning and end of the study period assessed the children. A seven-day assessment of food intake was made before, during and immediately after the period of dietary intervention in both groups. A blood sample was taken from each child for determination of food specific antibodies and in those children who could do so, the peak expiratory flow rate (PEFR) was measured. Based on the recommended nutrient intake (RNI), the mean percentage energy intake of the children in the experimental group was significantly lower (p < 0.05) in the experimental group. After the eight-week study period and compared with baseline values, the mean serum anti-ovalbumin IgG and anti-beta lactoglobulin IgG concentrations were statistically significantly reduced (p < 0.05) for both in the experimental group. In contrast, the values for anti-ovalbumin IgG in the control group were significantly increased and those for anti-beta lactoglobulin IgG were practically unchanged. The total IgE values were unchanged in both groups. Over the study period, the PEFR in those children in the experimental group able to perform the test was significantly increased, but no such change was noted in the children in the control group who could do the test. These results suggest that even over the short time period of eight weeks, an egg- and milk-free diet can reduce atopic symptoms and improve lung function in asthmatic children.

Development of immunoglobulin G subclass antibodies to ovalbumin, birch and cat during the first eight years of life in atopic and non-atopic children

Immune responses to allergens in young children include both Th1- and Th2-like immunity, which may regulate the secretion of immunoglobulin (Ig) G subclass antibodies differently. The time, route and level of exposure to an allergen may be decisive with regard to whether sensitization or tolerance will ensue. To study this, we investigated the development of IgG subclass antibodies to food and inhalant allergens during childhood. The study group comprised a cohort of 96 children participating in a prospective study. IgG subclass antibodies to ovalbumin, Bet v 1 and cat dander were analyzed at birth, 6 and 18 months and 8 years by ELISA. IgG1 and IgG3 subclass antibodies to ovalbumin peaked at 18 months and then declined up to 8 years of age, whereas antibodies to the inhalant perennial allergen cat, but not the inhalant seasonal allergen birch, increased with age. Exposure to cat and birch tended to be associated with high antibody levels to those allergens, whereas antibody levels to ovalbumin were not related to exposure to egg. The presence of positive skin prick tests and circulating IgE antibodies correlated with high levels of IgG subclass antibody responses to the allergens. Atopic symptoms were associated with high levels of IgG subclass, particularly IgG4, antibodies to the allergens. The difference in antibody levels between atopic and non-atopic children was most marked at 6 months for ovalbumin. For the seasonal inhalant allergen birch, the difference was apparent from 18 months, whereas a difference in antibody levels to the perennial inhalant allergen cat was already present at 6 months. In conclusion, IgG subclass antibodies to food allergens peak in early infancy and are then down-regulated, whereas antibodies to the inhalant perennial allergen cat, but not the inhalant seasonal allergen birch, increase with age. Atopy is associated with high levels of IgG subclass, particularly IgG4, antibodies to allergens, supporting a deviation of the immune system towards Th2-like responses in atopic children.

A role for the hepatobiliary system in IgE-mediated intestinal inflammation in the rat

BACKGROUND

For many years the central focus of research into gastrointestinal hypersensitivity reactions has been the mast cell population of the intestinal lamina propria. Since bile is known to deliver immunological mediators to the gastrointestinal tract, the possibility arises that extra-intestinal populations of mast cells may also contribute to IgE-mediated intestinal damage.

OBJECTIVES

To characterize hepatic mast cells in the rat and to investigate the role of the hepatobiliary system in a model of IgE-mediated reactivity to dietary antigen.

METHODS

Wistar rats were passively sensitized with monoclonal antidinitrophenyl (DNP) IgE antibodies, and were later challenged orogastrically with DNP-HSA. Additional animals were sensitized, then bile duct-cannulated prior to antigen challenge. At various time points, liver and intestinal samples were collected for histological examination, and bile was collected and assayed for histamine and TNFalpha.

RESULTS

Hepatic mast cells display a mucosal mast cell-like phenotype, and are closely associated with the vessels of the portal triads. Orogastric antigen challenge led to a rapid and significant decline (P<0.0001) in detectable mast cells as a result of anaphylactic degranulation. The median number of granulated mast cells associated with each portal triad in liver sections declined from six per portal triad to one per portal triad post-antigen challenge. After 15 min, biliary histamine concentrations rose above background levels (P<0.01). TNFalpha was also detectable in the majority (4/6) of bile samples within 15 min of challenge. Histological examination of the gastrointestinal mucosa revealed disruption to the villous epithelium ranging from oedematous changes to gross destruction. Such damage was not seen in animals in which bile had been externally drained.

CONCLUSION

The data indicate that biliary products are major contributors to the gastrointestinal damage arising from IgE-mediated hypersensitivity reactions in the rat, and such hypersensitivity reactions may involve a population of mast cells which reside in the liver.

Prevalence of IgG anti-Der p 2 antibodies in children from high and low antigen exposure groups: relationship of IgG and subclass antibody responses to exposure and allergic symptoms

Serum IgG PAN, IgG1-4, and IgE antibodies (Ab) specific for the house dust mite Dermatophagoides antigen (Ag) Der p 2 were measured by enzyme-linked immunosorbent assay (ELISA) in two groups of school children, age 12-14, exposed to high (Charlottesville, VA) and low (Los Alamos, NM) mite Ag levels in their environment. More than 90% of the children were found to have Der p 2-specific IgG antibodies, although the levels of both IgG PAN and IgG 1-4 Ab were substantially higher in the high exposure group (P = 0.001). In addition, there was considerable overlap between these two groups in all Ab measurements. The presence of IgG anti-Der p 2 Ab in the Los Alamos children was unexpected and suggests continuing Ag exposure, although the source of such exposure is not apparent. There is no correlation between RAST (+) and RAST (-) subjects with respect to the level of IgG Ab measured by ELISA. These results suggest that the IgG Ab response to house dust mite has been underestimated in the RAST negative population. Two twin pairs were included in this study and the divergent and varied Ab responses in these individuals indicate that factors in addition to environmental exposure and genetic susceptibility require further investigation and provide evidence for the complexity of the pathogenesis of the allergic response.

A case retaining contact urticaria against egg white after gaining tolerance to ingestion

A girl, 5.7 years old, gained tolerance to egg white ingestion in spite of high immunoglobulin E (IgE) antibody titers to egg white but retained contact urticaria against egg white. She developed atopic dermatitis on her face at 2 months of age and showed high IgE antibody titers to egg white and cow's milk. Accidental ingestion of egg products initiated immediate symptoms such as wheezing, urticaria, erythema and edema of the eyelids and conjunctiva three times. These symptoms were confirmed by challenge tests using boiled egg white at 3.9 years of age. She also reacted positively to a 20 min patch test on her volar arm with raw egg white. However, there were no reactions to the oral challenge test by boiled egg and freeze-dried egg white at 5.1 and 5.7 years of age, respectively. This non-responsiveness was confirmed by a double-blind, placebo-controlled food challenge using freeze-dried egg white. Nevertheless, she showed positive reactions to a 20 min patch test with freeze-dried egg white. Her IgE antibody titers to the egg white components including ovomucoid, ovalbumin, ovotransferrin and lysozyme as well as egg white were high from 2.9 to 5.7 years old. Her IgE antibody titers for the ovomucoid fragments digested by pepsin, chymotrypsin and trypsin were not lower than those of positive control subjects. The binding activity of IgE antibody to ovomucoid, however, decreased from 2.9 to 5.6 years as shown by radioallergosorbent test (RAST) inhibition assays. The IgE antibody showed weaker binding activity to pepsin- and chymotrypsin-digested ovomucoid that were filtered through cut-off 10,000 filter at the age of 2.1 and 5.7 years. We speculated that the maturation of secretion of digestive enzymes was involved in the mechanisms of the acquisition of tolerance to egg white ingestion in spite of the persistence of contact urticaria.

Immunogenicity and antigenicity of a partially hydrolyzed cow's milk infant formula

We evaluated the immunogenicity and antigenicity of a formula based on partially hydrolyzed cow's milk whey protein in infants at risk of atopy and in controls. Total IgE and specific IgE, IgG, and IgG4 subclass antibodies against egg albumin and cow's milk alpha-lactalbumin, casein, and beta-lactoglobulin were measured by radioimmunoassay of cord blood and of peripheral blood at 5 days and 6 months of life in five groups of infants: 16 breast-fed infants at risk of atopy (group 1), 21 partially hydrolyzed whey formula-fed infants at risk of atopy (group 2), 14 formula-fed infants at risk of atopy (group 3), 10 breast-fed control infants (group 4), and 13 formula-fed control infants (group 5). Total IgE concentration was significantly lower in group 2 at 6 months than in groups 3 and 5 infants and similar to that observed in groups 1 and 4 infants. The concentration of specific antiegg and anti-cow's milk protein IgG and of specific anti-cow's milk alpha-lactalbumin and beta-lactoglobulin IgG4 subclass antibodies was significantly reduced in group 2 as compared to group 3 infants and similar to that found in breast-fed infants. In conclusion, the partially hydrolyzed formula was less immunogenic and antigenic than a traditional formula and was as immunogenic and antigenic as breast milk.

The contrasting effects of CD8+ T cells on primary, established and Nippostrongylus brasiliensis-induced IgE responses

Recent data have indicated that CD8+ T cells suppress rodent IgE responses. In this study we investigated the effect of CD8+ T cells on primary and established IgE responses in euthymic and athymic nude rats. Euthymic PVG rats were depleted of CD8+ T cells by intraperitoneal injection of a CD8-specific monoclonal antibody (OX8), which resulted in an apparent loss of 92% of splenic and 98% of peripheral blood CD8+ T cells. The CD8+ T-cell depleted animals failed to mount a significant IgE response compared with control animals given an irrelevant monoclonal antibody (OX21). Furthermore, PVG nude rats reconstituted with purified CD4+ thoracic duct lymphocytes (TDL) alone failed to mount a significant IgE response, while animals given unfractionated TDL (containing CD4+ and CD8+ T cells) did. Depletion of CD8+ T cells 7 days prior to immunization and subsequent reconstitution at the time of immunization restored the IgE response. In contrast, removal of CD8+ T cells 1 month after induction of IgE by immunization with ovalbumin (OVA) and ricin prolonged the IgE response. In all cases IgG antibody responses were unaffected by the presence or absence of CD8+ T cells. This study shows that some CD8+ T cells are required for IgE, but not IgG, production to soluble antigen in a primary immune response. However, later in the immune response CD8+ T cells were shown to inhibit IgE production. These effects were apparently restricted to the immune response to soluble antigen, as Hooded Lister rats infected with 9000 larvae of the nematode Nippostrongylus brasiliensis produced high sustained levels of circulating IgE, in excess of 10 micrograms/ml, regardless of whether CD8+ T cells were depleted before or 1 month after infection.

Specificity of ELISA for IgG subclass antibodies against inhalant antigens in early childhood

ELISA is increasingly used to measure antibodies in new circumstances. Recently, it has been applied to the measurement of IgG subclass antibodies against common antigens in early childhood. These studies have raised concerns about the specificity of some of these assays. This paper details the results of experiments which have assessed the specificity of IgG1 binding to allergens of dust mite (Dermatophagoides pteronyssinus) and ryegrass (Lolium perenne) pollen by inhibition ELISA in the sera of 2-year-old children of atopic parents. Six sera which showed binding of IgG1 to D. pteronyssinus and six to L. perenne were used. All had IgG1 antibody against ovalbumin. In the children's sera, binding to D. pteronyssinus was substantially inhibited by preincubation with the homologous antigen, but not with ovalbumin, thereby confirming the specificity of the assay. However, suppression of IgG1 binding to L. perenne with the homologous antigen was comparatively small, and ovalbumin could cause an equivalent inhibition, indicating poor specificity. Furthermore, the level of IgG1 binding to L. perenne was closely correlated to the level of IgG1 binding to ovalbumin (r = 0.98; P < 0.001). When the assay was reversed, IgG1 binding to ovalbumin was only slightly inhibited by L. perenne, indicating that most antibody binding to ovalbumin was specific. Thus, binding IgG1 in both adult and child sera to D. pteronyssinus appeared to be specific, while child, but not adult, IgG1 binding to L. perenne showed poor specificity. This disparity may be due to differences in the affinities of the respective antibodies, and it illustrates the importance of determining assay specificity when making measurements in early childhood.

Risks of milk formulas containing peanut oil contaminated with peanut allergens in infants with atopic dermatitis

Four cases of infants with atopic dermatitis are reported. In all cases, a sensitization to peanut is demonstrated. Any ingestion of peanuts can be excluded, with the exception of a daily consumption of peanut oil, contained in milk formulas. Oral challenges with peanut oil induce a rash, and elimination of these brands is followed by the disappearance of eczematous lesions. The presence of residual allergenic proteins in peanut oil is thus suspected. Owing to the growing incidence of peanut hypersensitivity, the elimination of peanut oil from all milk formulas, food for babies, and ointments, seems to be highly advisable.

A prospective study of humoral immune responses to cow milk antigens in the first year of life

Previous studies have shown that in cow milk allergy the specific immune response to dietary cow milk antigens is deficient. This study aimed at delineating the development of humoral immune response to cow milk antigens in healthy infants. Twenty-five healthy newborns were enrolled, and seen at scheduled visits at the ages of three, six and eleven months, and they formed two groups: those breastfed and those fed adapted cow milk formulae. The local immune response in the gut was approximated using the ELISPOT assay of circulating antibody secreting cells. At the age of three months, in the formula fed group, cells secreting specific IgA to cow milk antigens were detected despite low levels of IgA serum antibodies. The total number of IgA secreting cells increased with age (p = 0.001). The milk in the infant diet directly influenced this development so that the age related increase was significantly greater in the formula fed group (p = 0.04). The results indicate that diet has a significant effect on the developing immune system, and that healthy infants are able to respond in an antigen specific fashion to dietary antigens, which may be central in attaining clinical tolerance of such antigens.

Allergenicity and antigenicity of chicken egg ovomucoid (Gal d III) compared with ovalbumin (Gal d I) in children with egg allergy and in mice

When attempting to generate mouse monoclonal antibodies to hen's egg ovalbumin, injection of commercially purified ovalbumin resulted in monoclonal antibodies, which when assayed against commercially purified ovalbumin (Gal d I) or ovomucoid (Gal d III), appeared to be specific to both. With the use of high-performance liquid chromatography (HPLC)-repurified ovalbumin and ovomucoid in assay procedures, monoclonal antibodies generated by commercially purified ovalbumin were found to be specific for ovomucoid only. To clarify this phenomenon, mice were serially injected with commercially purified ovalbumin or HPLC-repurified ovalbumin. It was found that most of the antibody response to commercially purified ovalbumin was directed against the minor (< 1%) ovomucoid contaminant and that HPLC-repurified ovalbumin failed to produce antibodies to ovomucoid. Commercially purified ovomucoid resulted in only minimal amounts of antibodies to ovalbumin. Thus when commercially purified ovalbumin is used both for immunization and immunoassay, most of the antibodies produced are actually against the small amount of ovomucoid contaminant, and not ovalbumin. To determine whether ovomucoid is the major antigenic and allergenic egg white protein in human beings, one group of 18 children with egg allergy were skin prick tested with half-log dilutions of egg white extract and diethylaminoethyl cellulose (DEAE)-repurified ovomucoid, ovalbumin, and lysozyme. Ovomucoid mean wheal diameters were significantly greater than wheal diameters in response to ovalbumin, lysozyme, and egg white extract at the three most concentrated of five dilutions tested: 0.01, 0.03, and 0.1 mg/ml (p < 0.01). Serum ovomucoid-specific IgE and IgG antibody concentrations to DEAE-repurified ovomucoid were significantly greater than that to DEAE-repurified ovalbumin (p < 0.05). In a second study, 10 patients with egg allergy and persistent egg hypersensitivity were compared with 11 patients with egg allergy in whom clinical tolerance to egg developed. IgE antibodies to repurified ovomucoid were significantly greater in patients with persistent egg hypersensitivity compared with patients in whom clinical tolerance developed at the time of both initial and follow-up food challenges. In contrast, there were no significant differences in IgE antibody concentrations to repurified ovalbumin in either group at any time. These results suggest that ovomucoid is the immunodominant protein fraction in egg white and that the use of commercially purified ovalbumin has led to an overestimation of the dominance of ovalbumin as a major egg allergen and antigen in human beings.

IgG subclass antibodies against Parietaria judaica in normal and allergic subjects

IgG antibody response to the inhalant allergen Parietaria judaica (Pj) and IgG subclass distribution were studied in 82 normal subjects, divided into three groups according to age (0-1, 1-20, and 20-60 years) and in 32 allergic subjects aged 20-60 years. Both normal and allergic subjects showed an IgG response, and all had IgG1 antibodies specific for PjE. Serum IgG2, IgG3, and IgG4 against PjE were detectable in 36%, 46%, and 22% of normal subjects, and in 58%, 31%, and 65% of allergic subjects, respectively. A significant difference in class distribution between allergic and age-matched normal subjects was found only for IgG4 antibodies against PjE (65% and 17%; P < 0.01). The ELISA results were also analyzed quantitatively, taking into account the relative proportion of specific antibodies. Thus, in normal subjects IgG1 antibodies showed a decreasing trend as the age rose, while no differences according to the age of the subject were found for IgG2 and IgG4. When data from allergic subjects (20-60 years) and the age-matched normal group were compared, they were different for the relative percentage of IgG2 only, showing for this a significantly lower value (P < 0.001). The present data indicate that normal and allergic subjects show differences in the IgG isotype distribution depending on their sensitivity and duration of allergen exposure.

The functional affinities of antibodies of different IgG subclasses to dietary antigens in mothers and their babies

The quantity and functional affinities of IgG1 and IgG4 antibodies to the dietary antigens casein and ovalbumin were measured in unselected mothers and their 1-year-old infants. In these infants, the titre of IgG antibodies to both antigens was highest in the IgG1 subclass, while in their mothers the titre of IgG1 and IgG4 antibodies to these foods was similar. High affinity IgG4 responses to both casein and ovalbumin were frequently found in mothers, whilst IgG1 responses, particularly to ovalbumin, were of low functional affinity. By contrast, in the 1-year-old infants, the functional affinity of IgG1 antibody to ovalbumin was substantially higher than in their mothers (Student's paired t-test, P < 0.001), indicating that higher affinity IgG1 antibody was produced on first exposure to ovalbumin rather than following chronic exposure. The effect of antigenic load on affinity maturation was further investigated by comparing the affinity of IgG1 antibody to casein in bottle, mixed and breast fed infants. Bottle fed infants had significantly higher-affinity IgG1 antibodies to casein compared with breast or mixed fed infants (Student's unpaired t-test, P < 0.01 and 0.02), suggesting that antigen exposure via the gut was able to drive the affinity maturation process. In studying the immune response it is clear that account must be taken of the affinity as well as of the titre of the antibody produced.

Allergenicity of cow milk proteins

The allergenicity and antigenicity of cow milk proteins are age dependent. Because the nonspecific and specific factors inhibiting the passage of cow milk proteins through the epithelial layer of the intestine are deficient at birth, although developing during early infancy, allergy to cow milk may be acquired during the first year of life. Allergic reactivity to cow milk is lost during childhood in the vast majority of cases. This change may depend at least partly on the development of the local immune system of the gut producing antigen-specific IgA antibodies. Circulating IgG antibodies to cow milk proteins are always produced when an infant has cow milk in the diet but are not associated with allergy; their titer is reduced with age. Clinical challenge tests show that most cow milk-allergic patients react to several protein fractions of cow milk. A patient may have IgE antibodies to several fractions of cow milk, measured either by skin testing or by radioallergosorbent test. Likewise, various tests for cell-mediated immunity may show positive reactions to several fractions. No single major allergen is apparent in cow milk, according to either the challenge tests or laboratory procedures: casein, alpha-lactalbumin, and beta-lactoglobulin all show a high proportion of positive reactions.

Early immune responses to Dermatophagoides pteronyssinus and atopic predisposition

Responses to the house dust mite during infancy may be important determinants of asthma in susceptible individuals. This study assessed early IgG subclass antibody responses to Dermatophagoides pteronyssinus in children of atopic parents. Sixteen atopic and 15 non-atopic children were selected from a birth cohort, and atopic status was established according to follow up over the first two years. IgG1 and IgG4 antibodies to D pteronyssinus were measured by enzyme linked immunosorbent assay at 7 days and 3, 6, 12, and 24 months. In all children D pteronyssinus IgG1 fell at 3 months (indicating maternal antibody loss), rose progressively to 12 months, and waned at 24 months. D pteronyssinus IgG4 was only detectable at 7 days. Children who were atopic by 2 years and therefore at greater risk of asthma, tended to have higher D pteronyssinus IgG1 at 6 and 12 months. These data suggest greater exposure or responsiveness to dust mite during infancy than in the second year.

The IgG subclass antibody response to an inhalant antigen (Dermatophagoides pteronyssinus) during the first year of life: evidence for early stimulation of the immune system following natural exposure

This study investigates the early humoral immune response following natural exposure to an inhalant antigen (Dermatophagoides pteronyssinus) in 36 babies, from birth until 1 year of age. The total IgG and subclass 1 and 4 D. pteronyssinus-specific antibody levels were assayed in sera collected at 7 days, 3 and 12 months by ELISA. After an initial fall, due to the progressive loss of maternal antibodies, an IgG specific response to D. pteronyssinus was seen between 3 and 12 months. This was restricted to the IgG1 subclass when the values at 12 months were significantly higher than those detected at the third month (P less than 0.001, paired t test). No D. pteronyssinus-specific IgG4 antibody was detected in any subject at any of the time points tested. The present study demonstrates that inhalant as well as food antigens are able to stimulate the immune system during the first year of life and that the antibodies produced are of the IgG1 subclass.

Food allergy

Food allergy is now known to encompass a number of distinct clinical entities that follow the ingestion of specific food or food additives. Research continues to shed light on immediate reactions to foods and food protein-induced enterocolitis of newborns and infants. Adverse reactions to food additives remain an area of health concern. Studies of food allergies have entered an era in which improved clinical design is the hallmark of the research and conclusions may now be drawn reliably.