Prz Gastroenterol 2013; 8 (4)

IgG-dependent allergy and selected gastrointestinal diseases

Alergia IgG-zależna a wybrane choroby przewodu pokarmowego

 

Mirosława Gałęcka1, Patrycja Szachta1, Wojciech Cichy2, Anna Bartnicka1

1Institute of Microecology, Poznan, Poland

2Department of Paediatric Gastroenterology and Metabolic Disorders, First Division of Paediatrics, Poznan University of Medical Sciences, Poland

contact:pszachta@instytut-mikroekologii.pl

 

Abstract:

IgG-dependent allergy may be one of the causative or perpetuating factors for gastrointestinal diseases, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). Reactions in which IgG antibodies are involved result in more delayed responses compared to IgE-dependent allergy. Abnormal IgG-dependent reactions to food lead to the formation of immune complexes and, as a result, to the development of chronic inflammation. In spite of that, IgG-dependent allergy is considered controversial, as some scientists consider these reactions physiological. An elimination diet based on the results of IgG testing against specific food antigens is beneficial in the treatment of IBS and IBD.

 

Supplement:

The prevalence of diagnosed IgE-dependent food hypersensitivity is estimated at 5.4–9.3% in infants and 1.4–2.4% in adults. Meanwhile the prevalence of IgG-dependent allergy in Europe and the United States may be up to 45%. An increased risk of this type of allergic reaction is seen with selected functional and organic disorders of the gastrointestinal tract, such as irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD).

IgG-dependent allergy is directly caused by increased permeability of the intestinal barrier. When homoeostasis is preserved, this layer is tight and highly selective, so that only the desired nutrients enter the bloodstream from the intestinal lumen, while access of potentially noxious substances and pathogens is impeded. The analyses showed that damaged tight junctions between the enterocytes are the underlying abnormality of IgG-dependent food allergy. The correctly functioning tight junctions between the intestinal cells ensure that the barrier shows the required selectivity. Loosening of the tight junctions makes it possible for larger particles – not only nutrients but also toxins and microorganisms – to penetrate the barrier. The increased permeability of the intestinal barrier is referred to as leaky gut syndrome. Ingestion of food therefore leads to chronic activation of the immune system in which IgG antibodies are involved. This results in the development of chronic inflammation. The delayed nature of the reaction is a considerable diagnostic obstacle that makes it impossible for the patient to identify the factor causing the allergy.

The clinical manifestations of chronic IgG-dependent reactions depend on the target tissue or organ to which the immune complexes composed of IgG and the food antigens are transported with the bloodstream. High levels of the complexes accompany such dissimilar disease entities as migraine, irritable bowel syndrome, atopic dermatitis, chronic fatigue syndrome, Crohn’s disease, etc.  The signs and symptoms develop within 8–72 h after ingestion of the offending food. As mentioned above, patients do not associate a given symptom with the food they ate, especially because of the lack of the characteristic “allergic” symptoms. This is the fundamental argument that highlights the controversial nature of type III food allergy. Mild severity of the clinical manifestations or their complete lack is generally associated with a considerable delay of the reaction in time or with low titres of IgG in the blood (low permeability of the intestinal barrier). IgG-dependent food hypersensitivity may affect various organs and systems, such as the gastrointestinal tract (nausea, vomiting, diarrhoea, abdominal pain, lip oedema), skin (urticaria, erythema, rash, pruritus, angio-oedema), respiratory tract (rhinitis, sneezing, itchy throat, laryngeal oedema, hoarseness, cough, stridor, dyspnoea, asthma), cardiovascular system (tachycardia, hypotension, arrhythmia) and nervous system (dizziness, asthenia, fainting)

According to Isolauri et al., an elimination diet based on the results of the measurement of IgG levels may be equally beneficial in terms of symptom relief as is the case with IgE-dependent allergy. A study conducted in 2001 by York Nutritional Laboratory investigated the usefulness of an elimination diet used after determination of serum levels of the “controversial” IgG antibodies.  As many as 50% of the subjects observed a considerable improvement of health after introduction of the elimination diet and 70% reported health benefits. Atkinson et al. showed that an elimination diet can be effective in relieving the symptoms of IBS. After 12 weeks of the diet a 10% improvement in well-being and resolution of the symptoms were observed (p = 0.024). The quality of life also improved. Drisco et al. conducted a study in 20 patients meeting the Rome II criteria for IBS. The patients followed a diet for 6 months that was based on he results of the tests for IgG-dependent allergy. The study showed abnormal titres of IgG antibodies specific for selected food components in all the patients. Using a diet based on the results of IgG-dependent allergy testing led to a statistically significant improvement in symptoms (improved stool frequency, pain relief) (p = 0.05) and the quality of life (p = 0.0001). The justifiability of using a diet based on the results of the tests assessing type III allergy has also been shown in patients with Crohn’s disease The  pilot study was conducted in 79 adult patients with Crohn’s disease. The control group consisted of 20 healthy volunteers. The study showed markedly higher serum levels of IgG in patients with organic bowel disease compared to the control group. Following a diet based on the results of the measurement of specific IgG for food antigens considerably improved stool frequency, pain and patients’ well-being. Decreased secretion of interferon γ (IFN-γ) by T cells was also observed. However, a necessity is emphasised to carefully select research tools, i.e. tests that are based on reliable methods and that assess the correct parameter. The best tools for the assessment of type III allergy are assays that assess all the IgG subclasses (IgG1–IgG4) quantitatively (ELISA). Tests for IgG-dependent allergy should be regularly validated for the assessment of actual diagnostic parameters.

 

References:

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  2. Audit of the York Nutritional Laboratory survey, conducted by the Department of Health Studies, University of York, on behalf of the British Allergy Foundation
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