Why measurement if IgE, IgG Total, IgG4 and Complement are Important Collec-tively for Understanding a Reaction to Food.

What Complement Proteins Should Be Measured?

Worldwide, there is significant increase in allergies and sensitivities, and the rate of increase is not
slowing down. The past 50 years have resulted in a dramatic increase in incidents. The significant
change in rate of allergies indicates that there must be an environmental influence, as genetics do
not shift in such a short period of time. There are estimates that speculate the sensitization rate
to one or more allergens in school children is approaching 40-50%. Currently, 32 million people in
the United States have food allergies. The CDC states there has been a 50% increase from 1997 to
2011, and the rate of tree nut allergy has as much as tripled in the last two decades. 1 2 3 The
increase is due to increase in respiratory environmental exposure, changes in what we eat,
pesticides in food and over exposure to smaller amounts of food. Also, theories such as the
“hygiene” hypothesis explain that as we have become more hygienic, our immune system is less
able to become tolerant to exposures increasing allergies. Other factors include excessive use of
acetaminophen, antibiotics, Vitamin D deficiency and obesity. 4
The most familiar allergic reaction is the IgE mediated response. When IgE binds to mast cells or
eosinophils it triggers an allergic reaction causing a release of histamine, or other inflammatory
mediators. IgE can be measured in both the serum and on the skin, via skin prick testing. Results
should be similar, but they will not correlate 100%, given there are slight differences in the
immune environment of the skin vs the blood. An IgE mediated reaction is measured to confirm
the presence of an allergy. In the strictest sense, an allergy is a clinical diagnosis, meaning it is
based 100% on the presence of a reaction after a particular exposure. IgE testing is then used to
confirm this allergic response and verify that the suspected allergen in the patient. It is well
established that IgE will only be present 50% of the time when there is a reaction to an allergen,
such as a food like dairy and wheat. IgE testing alone, will only identify 50% the global reactivity
and subsequent food related symptoms a person is experiencing.

The Emerging Role in Comprehensive Assessment
of Food Sensitivity and Allergy Screening

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What Complement Proteins Should Be Measured?

Why measurement if IgE, IgG Total, IgG4 and Complement are Important Collec-
tively for Understanding a Reaction to Food.

• Gupta RS, Warren CM, Smith BM, Jiang J, Blumenstock JA, Davis MM, Schleimer RP, Nadeau KC. Prevalence and Severity of Food Allergies Among S Adults. JAMA
• NetworkOpen2019;2(1).
• United States Census Bureau Quick Facts (2015 and 2016 estimates).
• Gupta RS, Warren CM, Smith BM, Blumenstock JA, Jiang J, Davis MM, Nadeau KC. The Public Health Impact of Parent-Reported Childhood Food Allergies in the United
• States. Pediatrics 2018; 142(6):e20181235.
• https://www.aaaai.org/conditions-and-treatments/library/allergy-library/prevalence-of-allergies-andasthma#:~:text=A%20leading%20theory%20behind%20the,between%20harmless%20and%20harmful%20irritants

There are a number of reasons that an IgE
titer is only positive 50% of the time. One is
that not all responses to foods are allergies.
An IgE reaction is known as a Type I
Hypersensitivity reaction. A type I
Hypersensitivity reaction is designed to
protect the body from invasion by a
pathogen. The normal response to an
invading pathogen occurs when an IgE
antibody binds to the pathogen and signals
a cascade of other immune compounds to
be to the area, and ultimately lyse (secrete
enzymes to break down) or kill the invader.

Going forward, the antibody-antigen complex trains the immune system to recognize the
antigen(invader) faster upon subsequent exposure. In the case of an allergen, the immune
system is now recognizing something from the environment, either a food or environmental
trigger, and this heightened sensitivity of immune reaction leads to the release of chemokines,
cytokines, and other inflammatory compounds. These inflammatory compounds can lead to a
variety of symptoms and even direct the patient’s chemistry toward medical conditions.
An increase in inflammation can be driven by histamine reactions, and we know that histamine
receptors are not just in the skin and lungs, but also in the brain, heart, kidneys, GI tract and
uterus. This explains why histamine and allergies can have a wide-reaching effect on virtually
every organ system in the body. Again, 50% of the time when an allergen causes a symptom,
there is no positive IgE response. It is important to characterize the total immunologic response
in order to help patients overcome their allergen and sensitivity symptoms and help them to
improve their quality of life.
The immune system can react in a number of ways. Type I hypersensitivity is IgE driven, but
another reaction known as Type II is IgG driven. Both parts of the immune system can be
activated, so we can also mount an IgG response to foods. While an IgG response if not an allergy
by definition, it still creates an inflammatory reaction to food and is known as a sensitivity
response. It is different than an IgE response, in that the IgE reaction will result in symptoms
immediately and can be anaphylactic, however the IgG mediated reactions will occur 3-72 hours
later, in general. IgG will not create an anaphylactic response, but it upregulates on-going
low-grade inflammation that can contribute to initiating symptoms or making many conditions
worse.

Some practitioners dismiss IgG because IgG creates generalized inflammation and is not specific
enough to consider. IgE reactions creates a smaller set of identifiable and in general immediate
symptoms. IgG, because it increases inflammation, can make most underlying conditions worse.
In essence, the value of IgG testing is that it helps determine another contributing factor to
metabolic inflammation.
Because IgG can contribute to a wide set of symptoms, this type of reaction may be dismissed as
nonspecific. However, medical literature does clearly identify the fact that those with higher IgG
reactions to foods, are likely to have more symptoms than those who have less. Additionally, there
are particular conditions that tend to have an increased of an IgG response, and it makes sense to
consider these reactions as a part of a treatment plan in order to reduce total immune burden on
those conditions that show consistent IgG elevation.

Critics say there is no data that supports the use of IgG in food reaction testing. Much of the
evidence that is used to support that assumption is dated. Insurance companies for example, will
often suggest that there is no association with IgG and pathology, but their references are
generally from the 1980s or earlier. As our understanding of immunology improved so did our
understanding of food reactions. Just like we learned that there was more than type I
Hypersensitivity in response to infection, we learned that immune cross reactivity and heightened
immune signaling that occurs in type I-IV Hypersensitivity. In Type II, IgG mediates a reaction, and
just as our body mounts this response to infections, it can mount a similar response to foods.
Type III and IV are also subsets of reactions driven by immune response in allergies and
sensitivities. Current research has pointed to multiple examples of serum levels of IgG antibody
testing to foods positively correlated to clinical symptom patterns and pathology.
The published evidence around IgG response is exploding, in 2019, there were over 400
publications around IgG reactions to foods. Whereas before 2000, there were generally around
100 publications a year. This demonstrates that our understanding of how IgG reacts to foods
has grown enormously.

Graph from PubMed showing the increase in studies concerning IgG and reactions to foods.

A study done in 2016 helps to confirm the role of IgG in unexplained symptoms as IgG was found
elevated in patients presenting with allergic symptoms, but with no laboratory evidence of IgE
antibodies. It was established that IgG was increased in patients with symptoms such as urticaria,
typically believed to be mediated by IgE, compared to controls, demonstrating a role of IgG
reactions in histaminergic reactions. They conclude that IgG antibodies play a role in allergic
symptoms and should be measured when IgE is not present. 5 A number of studies show a
connection between migraines and diet induced inflammation. 6 It has been increasingly identified
that if patients who has migraines also has IBS, significant improvement is noted when IgG
elimination style diets are utilized. This helps us to establish the connection between gut based
inflammation and systemic symptoms. 7 IgG food reactions have been identified to be involved in
ankylosing spondylitis, 8 abdominal pain, diarrhea, distention, stool shape and distress, 9
Non-celiac wheat sensitivity, 10 IBS, 11 IBD, 12 13 14 15 16 and Autism. 17In Rheumatoid Arthritis, IgG
antibodies to foods have been found in the synovial fluid at higher rates than in controls,
demonstrating that IgG cross reactivity to food is involved in the autoimmune reaction in the
joints. 18 IgG is also higher in atopic patients, but different subsets of IgG are higher depending on
the food, again showing the importance of having measurements of multiple antibodies. 19
Other connections that support the role of IgG being inflammatory are shown in a study in which
subjects with diarrhea and constipation were measured for IgG antibodies to wheat and cereal. It
was found that the group that higher levels of IgG also had higher levels of intraepithelial
lymphocytes showing immune-inflammatory changes in the digestive tract, similar to levels seen
in Celiac disease and Colitis. 20 While not diagnostic for Celiac disease, IgG antibodies have been
shown to be increased in this condition, specifically IgG1 and IgG3, which is the majority of total
IgG, with a decrease in IgG4. 21

• The value of eliminating foods according to food-specific immunoglobulin G antibodies in irritable bowel syndrome with diarrhoea. J Int Med Res.
• 2012;40(1):204-10.
• Frequency of determining markers of casein’s inhability and gluten in children with disorders of autistic spectrum Bavykina IA, Popov VI, Zvyagin AA, Bavykin DV.
• Vopr Pitan. 2019;88(4):41-47. doi:10.24411/0042-8833-2019-10040
• Atkinson W, Sheldon TA, Shaath N, Whorwell PJ. Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut.
• 2004;53(10):1459-1464. doi:10.1136/gut.2003.037697
• Cai C, Shen J, Zhao D, et al. Serological investigation of food specific immunoglobulin G antibodies in patients with inflammatory bowel diseases. PLoS One.
• 2014;9(11):e112154. Published 2014 Nov 13. doi:10.1371/journal.pone.0112154
• Jian L, Anqi H, Gang L, et al. Food Exclusion Based on IgG Antibodies Alleviates Symptoms in Ulcerative Colitis: A Prospective Study. Inflamm Bowel Dis.
• 2018;24(9):1918-1925. doi:10.1093/ibd/izy110
• Atkinson W, Sheldon TA, Shaath N, Whorwell PJ. Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut.
• 2004;53(10):1459-1464. doi:10.1136/gut.2003.037697
• Treating Irritable Bowel” by Drisko, et al Journal of American Nutrition Vol. 25 #6 514-522 Pub. 2006
• “Delayed Onset Food Allergies” by Melletis, C. and Barker, J. Alternative and Complementary Therapies, Pg. 61-65 April 2003
• Bavykina IA, Popov VI, Zvyagin AA, Bavykin DV. Vopr Pitan. 2019;88(4):41-47. doi:10.24411/0042-8833-2019-10040
• 2006 Sep;55(9):1240-7. Feb 16. The gut-joint axis: cross reactive food antibodies in rheumatoid arthritis
• Morris ER, Hampton SM, Morgan JB. IgG subclasses to food proteins in atopic and normal individuals. Ann Nutr Metab. 1993;37(1):39-43. doi:10.1159/000177747
• Mędrek-Socha M, Błońska A, Konrad P, et al. Liczba limfocytów śródnabłonkowych w przewodzie pokarmowym u osób z IgG-zależną nietolerancją pokarmową [The
• number of intraepithelial lymphocytes in digestive tract in patients with IgG-dependent intolerance of cereal products]. Pol Merkur Lekarski. 2018;45(270):237-241.
• Hvatum M, Scott H, Brandtzaeg P. Serum IgG subclass antibodies to a variety of food antigens in patients with coeliac disease. Gut. 1992;33(5):632-638.

Another issue health care providers have with IgG reactions, is that IgG subtypes behave
differently, are distinct and therefore you cannot effectively evaluate them when they are
measured as a total group. This is demonstrated in the study above, in which Celiac patients had
an increase of IgG1 and 3 but a decrease in IgG4. Antibody activity is distinct, and it is best to
measure IgG4 separately. There are four isotypes of IgG, IgG 1-4. The understanding of various
antibody response has grown with the increase in published studies.
Previously, our understanding of IgG was limited, leading to some misconceptions in food
antibody testing. It was initially noted, that when IgE was higher, often IgG4 would be high as well.
Because it correlated with IgE to some degree, and more than the other isotypes such as IgG1-3,
some began to suggest that IgG4 might be the best marker for tracking sensitivity. Some labs even
began running IgG4 and touting it as a stand-alone marker of sensitivity. As our understanding of
immunology expanded, if was found that IgG4 could be seen with IgE because it is a response to
IgE. It is not an allergic response or sensitivity reaction, but it blocks the effect of IgE and create
immune tolerance. In fact, desensitization injections or allergy therapy work by increasing IgG4 via
IL-10 modulated response, creating tolerance.
Desensitization to mediators released from mast cells and basophils to allergen exposure is the
first change initiated with allergen immunotherapy. The mechanism responsible for this
desensitization has yet to be elucidated. As allergen dosing is increased in the course of
immunotherapy, the next response is a change in T cell subset distribution with the generation of
allergen specific T regulatory (T reg) cells and a decrease in Th2 cells. Repeated allergen exposure
stimulates IL-10 and TGF-β expression by allergen-specific, inducible, type 1, peripheral T
regulatory (Tr1) cells, which act in an autocrine fashion to further activate these Tr1 cells and
initiate peripheral tolerance.
Finally, the late changes include decrease in IgE production by B cells and an increase in IgG4 and
IgA serum levels. These changes are responsible for the clinical effect of ameliorating allergy
symptoms. 22 Probiotics and omega-3 fatty acids have been reported to work through increasing
IL-10, helping with immune tolerance. 23 24 The activity of IgG4 is quite distinct. It is smaller in size,
and more thiol bonds which allow it to adhere to IgE receptors, blocking the ability of IgE to bind
resulting in decreased reactions to allergens. IgG4 creates immune tolerance. In general, having
levels of IgG4 indicates a tolerance to an allergen, rather than a sensitivity. However, there is a
class of IgG-RD or IgG related disease, and if someone has a condition related to excessive
production of IgG4, clinically it makes sense to remove foods that are creating heightened IgG4
production to the food.

Understanding the Mechanism of Allergen Immunotherapy, Amber Luong, MD, PhD,
https://med.uth.edu/orl/2009/02/05/understanding-mechanism-allergen-immunotherapy/
de Moreno de Leblanc A, Del Carmen S, Zurita-Turk M, et al. Importance of IL-10 modulation by probiotic microorganisms in gastrointestinal inflammatory diseases.
ISRN Gastroenterol. 2011;2011:892971. doi:10.5402/2011/892971
Gutiérrez S, Svahn SL, Johansson ME. Effects of Omega-3 Fatty Acids on Immune Cells. Int J Mol Sci. 2019;20(20):5028. Published 2019 Oct 11.
doi:10.3390/ijms20205028

There is discussion that production of IgG antibodies can be generated to anything eaten if the
gut is permeable. However, this is not the case. While exposure to the food, and gut based
permeability could increase your chances of having both IgG reactions as well as IgE reactions, it is
not the only cause and food exposure is not predictive alone. In general, individuals do not have
sensitivity reactions to everything they eat. There are genetic or environmental reasons that
cause the immune system to become sensitive to a particular food. Outside of permeability, there
is an increased chance of food reactions based on immune response in the Peyer’s patches, part
of the lymphatic system of the gut. If there is improper immune queuing, the body will begin to
mount an immune response to a food, even in the absence of permeability. Permeability is an
important factor, but only one factor determining whether or not sensitivity to specific foods
develop. Testing becomes essential because you cannot isolate reactions merely from diet
history. Removing foods that create an inflammatory response helps normalize reactions, in
addition, gut based therapies can normalize the microbiome, improve sIgA and reduce
permeability is additionally helpful.

As stated, IgE will only have a positive titer 50% of the time when there is a known reaction to
food. Outside of IgE and even IgG, there are other ways the body can create symptoms to foods
including:

• Increase release serotonin,
• Increases in platelet activating factor
• Could have lower levels of complement receptors on their RBCs that clear inflammatory
  reactions causing them to be more reactive.

No methodology exists for isolating these responses to foods, so even the most complete test
cannot measure every type of reaction to food.

It is important to measure antibodies together because they do not act in isolation. It is
commonly taught that IgE is a Type I hypersensitivity, creating immediate symptoms, and that IgG
is Type II hypersensitivity creating delayed sensitivities 3-72 hours later. While this is generally the
case, there is also an interaction between IgE, IgG, complement, and even sIgA antibodies. For
example, if there is enough IgG present, it can cause more immediate symptoms. IgG can cause
an additive effect to IgE antibodies, increasing mast cell degranulation. 25 Both IgE and IgG will
become more reactive when complement is present. Another difference between IgG 1-3 and
IgG4 is that IgG4 does not readily bind to complement, and this causes it to be less inflammatory
compared to other IgG antibodies. Measuring both IgG and complement together further fine
tunes results. Complement can augment the effect of IgG 1000 to 10,000-fold so it is important to
look at IgG and complement together. 26 If sIgA, that lines the gut is low, this too effects IgG and
IgE titers. IgG and IgE specific to foods, will stay elevated for longer, as the body responds to its
first level of defense, sIgA being low. IgG and IgE increase to compensate for sIgA deficiencies. 27
All antibodies play a role, and they can interact to have a synergistic effect. This certainly means,
that when you see multiple types of immune response to a food or antigen, you are isolating the
more inflammatory challenge to the patient. Measuring multiple antibody reactions allows for a
more comprehensive picture allows for discovery of the most clinically important responses.
While there are different methods of food allergy and sensitivity testing available, the type that is
most represented in the literature is IgE and IgG testing. By far, the bulk of the research is done in
this area. This makes sense given, the major reason for pathology is immune confusion that is
augmented with antibody production. Production of antibodies and presentation of
antigen-antibody complex in the presence of complement is how inflammation is most typically
created. Measuring antibody response is the most direct way of measuring an inflammatory
response to foods. While other methods exist, such as a live cell analysis, there is little
peer-reviewed data exists tying this type of inflammation to pathology.
There is extensive research connecting a number of different pathologies to an increase in IgG
antibodies, and in the case of allergies, IgE antibodies. Complement is also well defined to drive
inflammation and damage to tissue, whereas there is little data exists to show that as a white
blood cell increases in size in response to a food there is also an association with various
conditions. Immune challenges creates confusion in immune response and is best documented
with various antibodies, IgE, IgG 1-3, IgG4 and complement, so the most comprehensive
evaluation of food reactions, is one that looks at multiple facets of the immune system together.

• J Korean Med Sci. 2002 Jun;17(3):375-80. Role of IgG, IgA, and IgE antibodies in nasal polyp tissue: their relationships with eosinophilic infiltration and degranulation.
• Suh KS1, Park HS, Nahm DH, Kim YK, Lee YM, Park K.
• Science. 1996 Jan 19;271(5247):348-50. C3d of complement as a molecular adjuvant: bridging innate and acquired immunity. Dempsey PW1, Allison ME, Akkaraju S,
• Goodnow CC, Fearon DT.
• Sandin A, Björkstén B, Böttcher MF, Englund E, Jenmalm MC, Bråbäck L. High salivary secretory IgA antibody levels are associated with less late-onset wheezing in
• IgE-sensitized infants. Pediatr Allergy Immunol. 2011;22(5):477-481. doi:10.1111/j.1399-3038.2010.01106.x