What is IgG?
IgG is the major antibody found in serum. IgGs are composed of two fragment antigen binding (Fab) regions that contain the antigen binding sites and the Fc region, which is responsible for most of the biologic activity of the antibodies (Figure 1). An antigen is a substance that causes the immune system to produce an antibody that specifically reacts with it. IgG-mediated reactions to food antigens may be delayed by several hours or days, whereas IgE food antibody reactions are quite immediate.
Human IgG is separated into four subclasses denoted IgG1, IgG2, IgG3, and IgG4. Each subclass varies in abundance and biological function. IgG1 and IgG3 are predominantly responsible for antibody protection against reinfection. IgG2 antibodies are opsonic (marking a pathogen for ingestion and destruction) and develop in response to carbohydrate polysaccharide antigens. IgG4 molecules function as skin-sensitizing immunoglobulins and are thought to block antibodies produced in response to chronic exposure to antigens.
Why Test IgG Sensitivities?
Immunoglobulin G (IgG) food testing is a useful guide for structuring elimination diets for patients with many chronic conditions. Individuals with neurological, gastrointestinal, movement, and behavioral disorders often suffer from IgG food sensitivities. People may continue to eat offending foods unaware of their potential adverse effects. Symptoms associated with food sensitivities may occur hours or days after the offending food was eaten because IgG food antibodies remain for a much longer time than IgE antibodies. IgE food allergy causes the release of histamine, producing an immediate hypersensitivity reaction. In contrast, IgG food sensitivity is triggered by the binding of complement to IgG food antigen complexes, causing an inflammatory response. This is a delayed hypersensitivity reaction in which symptoms appear anywhere from hours to days after eating the offending food. Elimination of IgG-positive foods may improve symptoms of irritable bowel syndrome, autism, AD(H)D, cystic fibrosis, rheumatoid arthritis, and epilepsy, according to numerous clinical studies.
Clinical Significance of IgG Testing
The clinical significance of IgG food testing was illustrated in an early article published by an otolaryngologist who reported that the majority of his patients had substantial health improvements after eliminating foods found positive by IgG food allergy testing. The study demonstrated a 71% success rate for all symptoms, achieving at least a 75% relief. Of particular interest was the group of patients with chronic, disabling symptoms, unresponsive to other intensive treatments. Symptoms most commonly improved (75%-100%) on the elimination diets included asthma, coughing, ringing in the ears, chronic fatigue, headaches, gas, bloating, diarrhea, skin rash and itching, and nasal congestion. The most common IgG food allergies were to cow’s milk, garlic, mustard, egg yolk, tea, and chocolate. A recent study reported that 93% of non-celiac, gluten-sensitive patients showed anti-gliadin IgG antibody disappearance after a six-month adherence to a gluten-free diet. The IgG disappearance was closely related to a significant improvement of both gastrointestinal and extra-intestinal symptoms. High IgG antibody levels have frequently been found in children with diabetes mellitus, Crohn’s disease, celiac disease, and in those considered to be obese. IgG food test results are often used to develop food antibody-guided exclusion/ elimination diets. The implementation of such diets has been shown to alleviate symptoms associated with nonceliac gluten sensitivity and food sensitivity-induced atopic conditions, reduce the frequency of migraine headaches, decrease the occurrence of diarrhea, decrease failure–to-thrive among children with cystic fibrosis, reduce symptoms of irritable bowel syndrome, improve rectal compliance, decrease stool frequency in Crohn’s disease, prevent seizures and hyperkinetic behavior in children with epilepsy, and ameliorate kidney function in glomerulonephritis. Food elimination diets also hold promise for the improvement of behaviors associated with attention-deficit hyperactivity disorder.
Significance of Total IgG Versus IgG4
The goal of IgG-mediated food allergy testing is to identify foods that are capable of triggering many adverse reactions. IgG1, IgG2, and IgG3 are all capable of causing inflammation. IgG1, IgG2, and IgG3 antibodies to food antigens form large immune complexes or lattices that activate complement proteins and increase inflammation. IgG4 antibodies to food antigens will not usually trigger inflammation because IgG4 antibodies do not bind complement. However high levels of these antibodies indicate the presence of immune reactions against food antigens. Similarly IgA antibodies are not as clinically significant due to their inability to bind complement and trigger inflammation.
While most laboratories only provide a measurement of IgG4 molecules, The Great Plains Laboratory provides a measurement of total IgG antibodies to various food-based antigens and Candida, a genus of yeast native to the GI tract. Testing for only IgG4 antibodies limits the ability of the clinician to identify those foods that may be causing significant clinical reactions in their patients. IgG4 antibodies usually represent less than 6% of the total IgG antibodies. The importance of measuring all subtypes of IgG antibodies is highlighted in an article by Kemeny et al. They found that IgG1 antibodies to gluten were elevated in all patients with celiac disease but none of the patients had elevated IgG4 antibodies to gluten.
The IgG and Candida Connection
The Great Plains Laboratory tests for Candida albicans (a microscopic fungal organism and pathogenic yeast) as part of IgG food allergy testing. High levels of IgG antibodies to Candida have been found in patients who reported many symptoms of yeast overgrowth. Candida problems are caused when the benign yeast form of Candida albicans transforms to its fungal form and produces a buildup of toxins in the body. Candida can overgrow areas of the intestinal mucosa resulting in numerous symptoms, including creating microscopic holes in the lining of the intestines, leading to what is commonly known as “leaky gut” syndrome. Candida albicans proteins may trigger an inflammatory response. A wide range of disorders have been linked to Candida overgrowth including autism, multiple sclerosis, depression, chronic fatigue, fibromyalgia, migraines, and irritable bowel syndrome. Immunocompromised patients with cancer or AIDS can have life-threatening complications if Candida enters the bloodstream, resulting in systemic candidiasis. Use of antibiotics, oral contraceptives, chemotherapy, anti-inflammatory steroids, and diets high in sugar and starch increase susceptibility to Candida overgrowth.
Research has revealed a relationship between health of the gastrointestinal tract and overall well-being. Imbalance between good and bad bacteria (dysbiosis) has been shown to worsen behavior disorders, hyperactivity, aggression, and cause fatigue. Evidence is mounting that dysbiosis impairs the immune system and contributes to food allergies, digestive disorders, nutritional deficiencies, and cognitive dysfunction. Using the Food MAP (which will include a separate report for Candida and brewer’s yeast) will help identify food allergies and Candida sensitivity that may be creating a variety of problems for patients. Practitioners may then recommend elimination of the identified foods and supplementation with various natural products that control Candida overgrowth and assist with healing of the gut. Depending on the levels of Candida and the severity of a patient’s symptoms, further testing may be recommended, including a Comprehensive Stool Test or Organic Acids Test.
0-25th percentile: insignificant
26th-50th percentile: low
51st-97.5th percentile: moderate
97.5th and higher: high
THE BENEFITS OF TESTING
IgG testing determines if food reactions are contributing to physical or mental symptoms, and much more quickly than eliminating and then reintroducing each suspect food one-by-one over a period of time.
Removal of highly reactive foods from the diet is a non-invasive therapy that often mitigates a patient’s symptoms.
Research and clinical studies suggest food allergies identified by IgG testing can be major contributing factors to many chronic health conditions.
Eliminating all identified IgG-positive foods after testing can reduce stress on the immune system, decrease inflammation (helping to heal “leaky gut”), resolve food cravings, and reduce the potential for eating disorders.
Multiple Analyte Profiling with xMAP® Technology
The bead-based immunofluorescent assay uses color-coded magnetic beads, which are covalently coupled to 190 different food proteins specific to each protein’s IgG target. The color-coding of the beads into spectrally distinct sets allows the simultaneous capture and detection of multiple food IgG analytes from a single reaction well.
The xMAP® bead-based immunoassay occurs on the surface of magnetic beads by adding a patient’s serum sample and observing the classic antigen /antibody interaction, detected by using a fluorescent labeled antibody. Laser-based analysis of the fluorescent signal response is proportional to the binding of food-specific IgG antibodies onto the beads.
The IgG Food Allergy Test is available as both Serum and Dried Blood Spot.
Serum: 1 mL of in a gold-topped SST or in a royal blue-topped no additive tube.
Dried Blood Spot (DBS): Four full circles of dried blood on the protein saver card is required.
Please note that the elimination of a food prior to sampling will reduce the ability for our laboratory to detect antibodies (allergies) to that food.
Please note that the elimination diet is based only on IgG testing. To be safe, testing for IgE antibodies to food allergens should be considered PRIOR TO BEGINNING an ELIMINATION DIET. If a patient has negative results for IgG antibodies, it does not necessarily mean he/she is negative for IgE, IgM, or IgA antibodies.