High anti-IgE levels at birth are associated with a reduced allergy prevalence in infants at risk: a prospective study

Evidence that FcRn mediates the transplacental passage of maternal IgE in the form of IgG anti-IgE/IgE immune complexes

BACKGROUND

The mechanism(s) responsible for acquisition of maternal antibody isotypes other than IgG are not fully understood. This uncertainty is a major reason underlying the continued controversy regarding whether cord blood (CB) IgE originates in the mother or fetus.

OBJECTIVE

To investigate the capacity of maternal IgE to be transported across the placenta in the form of IgG anti-IgE/IgE immune complexes (ICs) and to determine the role of the neonatal Fc receptor (FcRn) in mediating this process.

METHODS

Maternal and CB serum concentrations of IgE, IgG anti-IgE, and IgG anti-IgE/IgE ICs were determined in a cohort of allergic and non-allergic mother/infant dyads. Madin-Darby canine kidney (MDCK) cells stably transfected with human FcRn were used to study the binding and transcytosis of IgE in the form of IgG anti-IgE/IgE ICs.

RESULTS

Maternal and CB serum concentrations of IgG anti-IgE/IgE ICs were highly correlated, regardless of maternal allergic status. IgG anti-IgE/IgE ICs generated in vitro bound strongly to FcRn-expressing MDCK cells and were transcytosed in an FcRn-dependent manner. Conversely, monomeric IgE did not bind to FcRn and was not transcytosed. IgE was detected in solutions of transcytosed IgG anti-IgE/IgE ICs, even though essentially all the IgE remained in complex form. Similarly, the majority of IgE in CB sera was found to be complexed to IgG.

CONCLUSIONS AND CLINICAL RELEVANCE

These data indicate that human FcRn facilitates the transepithelial transport of IgE in the form of IgG anti-IgE/IgE ICs. They also strongly suggest that the majority of IgE in CB sera is the result of FcRn-mediated transcytosis of maternal-derived IgG anti-IgE/IgE ICs. These findings challenge the widespread perception that maternal IgE does not cross the placenta. Measuring maternal or CB levels of IgG anti-IgE/IgE ICs may be a more accurate predictor of allergic risk.

IgE is expressed on, but not produced by, fetal cells in the human placenta irrespective of maternal atopy

The prevalence of atopic diseases in children has increased during the last decades. Atopic symptoms usually appear early in life. This implies an early priming for atopic disease, possibly even at the fetal level. We therefore compared the presence and production of IgE in the local in utero environment during pregnancy in atopic and non-atopic women. Eighty-six women were included in the study. Fifty women were demonstrated to be atopics, based on clinical symptoms of atopic disease together with a positive Phadiatop and/or skin prick test. Placentas from these term pregnancies were obtained. Slices covering the full thickness of the placenta were cut clockwise around the umbilical cord and were analysed with immunohistochemistry. Surprisingly, numerous IgE+ cells, located primarily in the fetal villous stroma, were detected in a majority of the investigated placentas irrespective of the atopy of the mother or maternal or fetal total serum IgE levels. The placental IgE could not be demonstrated to be bound to IgE receptors, but was shown to be bound to fetal macrophages, possibly via FcgammaRI. No evidence was found for local fetal IgE production, although cells producing epsilon transcripts were occasionally detected in the decidua. We describe here the novel finding of numerous IgE+ cells in the human placenta, suggesting an hitherto unknown role for IgE in a successful pregnancy outcome, irrespective of whether or not the mother is atopic.

Autoanti-IgE antibodies in patients with allergic and idiopathic rhinitis

The pathophysiology of idiopathic rhinitis is unknown although evidence is accumulating to suggest that, in a proportion of patients, it may be a more localized form of allergic rhinitis in the absence of other atopic symptoms and markers. Anti-IgE is thought to be a systemic marker of atopy. This study compared serum IgG autoanti-IgE levels in patients with idiopathic rhinitis, perennial allergic rhinitis and normal controls. Serum samples were obtained from 19 patients with idiopathic rhinitis, 17 patients with perennial allergic rhinitis and 10 normal non-rhinitic controls. The presence or absence of IgG1 and IgG4 anti-IgE antibodies was detected using enzyme-linked immunosorbent assays. Eighty-eight percent of the patients with perennial allergic rhinitis had raised levels of autoanti-IgE antibodies in their serum. None of the controls or patients with idiopathic rhinitis showed raised levels (P < 0.001). Although patients with idiopathic rhinitis may exhibit clinical and pathological features of allergy, they do not show raised levels of anti-IgE in their serum.

Elevated cord serum IgE increases the risk of aeroallergen sensitization without increasing respiratory allergic symptoms in early childhood

BACKGROUND

Increasing prevalence of allergic disorders has focused attention on primary prevention. There is a need to improve the accuracy of early-life predictors of atopy so that the at-risk population can be accurately defined and preventive measures instituted.

OBJECTIVE

The predictive capacity of elevated cord IgE, with or without family history of atopy, to allergic symptoms and skin prick test (SPT) sensitization is evaluated in a birth cohort followed up prospectively for 4 years.

METHODS

A birth cohort of 1456 consecutively born children was recruited in 1989. Data were collected on family history of atopy and cord serum total IgE (cord IgE) was measured. Of these, 1218 children were seen in the clinic at 4 years to determine the development of symptoms and signs of allergic disease and 981 were skin tested to a range of common food and aeroallergens.

RESULTS

Of 1218 children reviewed at age 4 years, 218 (17.8%) had symptoms of respiratory allergy and, of those skin tested (n = 981), 192 (19.6%) reacted positively. Twice as many children with elevated cord IgE (>/= 0.5 kU/L) at birth became sensitized to aeroallergens by age 4 years (34.8% vs 17.3%, P < 0. 001). Positive predictive value (PPV) of elevated cord IgE for the development of aeroallergen sensitization was better than that of family history of atopy (34.8 vs 22.6%). Combining paternal atopy with elevated cord IgE substantially increased the predictive capacity (PPV 77.8%). Cord IgE levels did not correlate with clinical asthma or rhinitis at age 4 years and PPV for allergic respiratory symptoms remained poor at all cutoffs.

CONCLUSION

Cord IgE is better than family history for predicting atopy as defined by allergen sensitization and this predictive value can be further increased by combining cord IgE with paternal atopy.

Is atopic dermatitis predictable?

Atopic dermatitis (AD) is a common skin disease which affects 10 to 20% of the population, usually with onset during infancy. The frequency of AD appears to have increased over the past three decades. Attempts to identify parameters predictive of the development of AD have been made by many investigators during the last decades. Although genetic factors remain unmodifiable, avoidance of relevant trigger factors could modify the development of AD. This paper reviews and discusses findings of the last several years and outlines recent advances in genetic studies of AD. In spite of decades of intensive research and newly developed technology, the parental history of AD appears to be the most valuable predictive parameter. However, the predictive capacity is not sufficient to recommend it as screening instrument. At this time, a perinatal screening with the objective of primary prevention of AD does not seem feasible.

The anti-IgE/anti-FcepsilonRIalpha autoantibody network in allergic and autoimmune diseases

Basophil granulocytes and tissue mast cells and their mediators play a role in the pathogenesis of several immune and inflammatory disorders. Human basophils and mast cells (FcepsilonRI+ cells) can be activated through immunological interaction with the IgE-FcepsilonRI network. FcepsilonRI+ cells can be triggered by cross-linking between the Fab portions of IgE and multivalent antigens (direct anaphylaxis). 'Reverse type' anaphylaxis can occur through three distinct mechanisms: antibodies against the Fcepsilon portion of IgE (anti-IgE), antibodies against epitopes of the alpha chain of FcepsilonRI (anti-FcepsilonRIalpha) and anti-IgG acting on IgG-IgE complexes bound to FcepsilonRI. Anti-IgE autoantibodies are occasionally present even in normal donors and more frequently in a variety of allergic (chronic urticaria, atopic dermatitis and bronchial asthma) and autoimmune disorders (rheumatoid arthritis, lupus erythematosus and systemic sclerosis). IgG anti-IgE from a small percentage of patients induces the release of mediators from human FcepsilonRI+ cells. Some of the anti-IgE autoantibodies present in allergic patients are non-anaphylactogenic, thus representing a possible protective mechanism preventing the association of IgE with FcepsilonRI. Anti-FcepsilonRIalpha autoantibodies also occur in a significant percentage of patients of chronic urticaria and probably non-allergic asthma and some autoimmune diseases. Although anti-IgE and anti-FcepsilonRIalpha autoantibodies, present in a percentage of patients with immune disorders, are relevant to the pathogenesis of these conditions, much remains to be learnt about their immunochemistry, their prevalence and precise role in various inflammatory diseases.

Cord blood-IgE as risk factor and predictor for atopic diseases

BACKGROUND

Cord blood-IgE as risk factor or predictor for atopic diseases in infants has been discussed in a large number of papers with contradictory results. Our aim was to evaluate cord blood-IgE as risk factor and predictor for atopic dermatitis, recurrent wheezing and sensitization with emphasis on a clear-cut distinction between risk factor and predictor.

METHODS

A cohort of 1314 newborns was recruited in six German obstetric departments and followed-up for 5 years. Four hundred and ninety-nine infants (38%) were considered to be at high risk with at least two atopic family members and/or a cord blood-IgE value above the threshold of 0.9 kU/L. At follow-up visits, parents filled in a questionnaire, the infants were clinically examined, and blood samples were taken.

RESULTS

With regard to early onset atopic dermatitis up to 12 months we found that the odds ratios at the cord blood-IgE cut-off points of 0.70 kU/L and 1.25 kU/L with values of 0.53 and 0.32, respectively, were smaller than one (i.e. protective factors) and highly statistically significant. No significant association was found between elevated cord blood-IgE and recurrent wheezing. There was a strong positive association between elevated cord blood-IgE levels and sensitization at 12 months, but even in this case the predictive performance was rather poor: a maximum positive predictive value of 42% was attained with a cut-off point of 3.0 kU/L, but the sensitivity was only 10%.

CONCLUSION

We conclude that even when elevated cord blood-IgE levels are identified as a strong risk factor for sensitization, their poor predictive performance may make them useless as a basis for preventive measures.

Auto IgG anti-IgE and IgG x IgE immune complex presence and effects on ELISA-based quantitation of IgE in canine atopic dermatitis, demodectic acariasis and helminthiasis

Atopic dermatitis is a common allergic disease manifestation in dogs; however, there is no correlation between clinical disease and detectable total serum IgE. Auto antibodies of the IgG subclass against IgE may affect the detection of serum IgE by immunoassay and may be important in the regulation of IgE production by B cells. ELISA were developed to detect serum antibodies specific for IgE using a newly available canine monoclonal IgE of known antigen specificity, generated from a canine x murine heterohybridoma. To test for correlation of auto IgG anti-IgE levels with manifestation of atopic dermatitis, the sera from 101 atopic dogs were compared with sera from non-atopic dogs of various breeds, foxhounds manifesting clinical signs of demodectic acariasis and helminth parasitized random bred dogs for quantities of IgG anti-IgE measured in units/ml compared to a high titer standard serum. To test for serum effects on quantitation of IgE, known amounts of canine monoclonal IgE were added to various sera and measured by capture ELISA with detecting monoclonal antibodies specific for heat labile or heat stabile epitopes. Unheated sera from dogs manifesting clinical atopic dermatitis and helminth parasitized dogs had levels of IgG anti-IgE that were significantly lower than various breeds of dogs not manifesting dermatologic lesions and foxhounds manifesting demodectic acariasis. Heating sera at 56 degrees C for 3 h to denature the high affinity binding site on the IgE heavy chain caused a marked increase over non-heated sera in detectable IgG anti-IgE in almost all dogs. This increase was most profound in helminth-infected dogs and foxhounds manifesting demodectic mange with 7 fold increases each, respectively, and in atopic dogs with a 5 fold increase compared to 3 fold increases for clinically-normal springer spaniels and all soft coated wheaten terriers. The terriers demonstrated an association of lower heated serum values of IgG anti-IgE with manifestation of a familial syndrome of protein-losing enteropathy and protein-losing nephropathy. The ability of mouse anti-canine IgE monoclonal antibodies specific for either heat labile or heat stabile epitopes to detect canine monoclonal IgE added to sera in known amounts varied from serum to serum and at different concentrations of the same serum, but did not correlate with IgG anti-IgE values for these sera. The range of absolute levels of serum IgE in dogs showing little or no inhibition of detection of added IgE was < 0.5 ng/micromilligram to 2 micrograms/micromilligram. It was concluded that the increase in detectable IgG anti-IgE after heating sera indicates that IgG x IgE immune complexes are normally present in most dogs; however, the increase over uncomplexed IgG anti-IgE was most pronounced in dogs manifesting atopic dermatitis and demodectic acariasis. A quantitative comparison of IgG anti-IgE or IgG x IgE to total serum IgE was not made because the ability of monoclonal antibodies specific for either heat labile or heat stable epitopes on the IgE heavy chain to detect IgE added to serum, as well as innate serum IgE, was highly variable in different dilutions of serum from individual to individual.

Atopic dermatitis: an update

This review focuses on recent literature regarding the following clinical features of atopic dermatitis (AD); diagnostic criteria, epidemiology and genetics, provocative factors, predictors of disease development and markers of disease severity, therapy, and prognosis. For example, the frequency of AD appears to be increasing, perhaps in response to provocative factors such as food allergens and house dust mites. Determination of reliable markers for disease development may identify susceptible newborns and facilitate avoidance of relevant triggers. Immunomodulating therapy holds promise in the treatment of refractory AD, and new investigation has led to refinements in conventional modalities such as antihistamines and phototherapy.

The prevalence of IgG1 and IgG4 autoantibodies to IgE in patients with allergic and non-allergic rhinitis

In this study we have compared the levels of IgG1 and IgG4 autoantibodies to IgE in the sera of patients with allergic rhinitis and non-allergic rhinitis. A group of patients undergoing cosmetic nasal surgery, but who did not have rhinitis or any history of atopy, acted as control. The frequency of positive titres of IgG1 and/or IgG4 anti-IgE was 70% (14/20) in patients with allergic rhinitis, 50% (10/20) in patients with non-allergic rhinitis and 20% (4/20) in the control group. The mean titres of IgG1 anti-IgE and IgG4 anti-IgE were in the order allergic rhinitis > non-allergic rhinitis > controls. In the allergic rhinitis group levels of IgG1 anti-IgE (P = 0.0055) and IgG4 anti-IgE (P = 0.0028) were significantly higher than those found in the control group. The non-allergic rhinitis group also showed significantly higher levels of IgG1 anti-IgE (P = 0.0182) and IgG4 and anti-IgE (P = 0.0359) than the control group. The existence of IgG autoantibodies to IgE in both allergic and non-allergic rhinitis suggests a possible role for these antibodies in the disease process, particularly in patients whose symptoms are not due to an allergic trigger.

Anti-IgE therapy

Controlling the IgE response at either the synthesis level or the effector phase should have a profound impact on the allergic cascade. For more than a decade, researchers have focused on ways of interfering with the binding of IgE to its high-affinity receptor on proinflammatory cells. Several approaches have also been taken to antagonize the complex interplay of cytokines and cell-associated molecules (CD40, CD23) that are implicated in IgE synthesis. Recently, anti-IgE antibodies have been developed that are potent IgE antagonists. These antibodies are currently under clinical investigation as potential therapeutics for allergic disease.

Do autoantibodies to IgE play a role in IgE-mediated events?

Elevated blood levels of IgG anti-IgE are detectable in individuals exhibiting enhanced IgE production, namely those with allergic conditions and helminthic parasite infections. The fact that there are epitope-specific subpopulations of autoanti-IgE suggests that this autoantibody could potentially have multiple effects in immunological events involving IgE.