The Biomarker Handbook is a curated series that seeks to provide readers with insights on each biomarker we cover in our blood test packages and its relation to our body.
Half a century ago, the discovery of the first immunoglobulin E (IgE) was made. Since then, extensive follow-up research has led us to understand what IgE does in the body and how it plays its part in being an important biomarker for allergies and parasitic infections.
The Physiology of IgE
IgE is a protein; more specifically an antibody. Like the other five in its class, it is produced by the B-lymphocytes. These white blood cells are responsible for the production of all of the immunoglobulins. Their production is stimulated by a particular antigen which is specific for each class of antibody.
The main role of immunoglobulins, including IgE, is in the host defence mechanism and immune response of our body against different pathogens.
In a normal state of health, the total IgE in the blood is found in low levels. However, in certain circumstances these serum levels can increase, insinuating an underlying disease condition requiring further investigation.
IgE – an Important Allergic Biomarker
Perhaps the primary role of IgE is in allergies. During an allergic reaction, allergens and other antigenic particles trigger the release of IgE from B-lymphocytes. The level of circulating IgE, thus, increases and this immunoglobulin is responsible for a chain of events that lead to the release of histamine that causes the horrible signs and symptoms of an allergy.
A typical allergic reaction includes a runny nose, watery eyes, skin itching and rash, constriction of the bronchi, uncommonly vomiting and diarrhoea and sometimes even a fatal anaphylactic reaction. It is important to recognise the signs of an allergic reaction. If left untreated, these symptoms can exacerbate and become potentially life-threatening.
The first time the allergen is introduced to the body and the specific IgE antibodies are produced, the immune response is slow. This first exposure, also known as sensitisation, sensitises white blood cells to the specific allergen in question. However, re-exposure triggers an immediate hypersensitivity reaction with greater symptoms than that seen with the first exposure.
IgE levels in the serum are also markedly increased in cases of asthma and hay fever.
IgE for Parasitic Infections
Parasitic or helminthic infections are also a cause of increased IgE levels in the blood. When a parasitic infection occurs, the immune system responds by the activation of eosinophils and platelets, both of which are thought to be induced by circulating IgE. Studies have found that people that are deficient in this antibody have longer recovery periods for parasitic infections like Schistosomiasis than those who have normal IgE in the blood.
Testing for Total IgE
The total IgE blood test is a non-specific screening test that is used to detect the presence of allergy. The total IgE test measures the total amount of circulating IgE in the body but does not exactly pinpoint to which allergen is causing the particular allergic reaction.
If the level of IgE is found higher than the normal upper limit, it could indicate an allergy or a parasitic infection and even asthma.
On rare occasions, a total IgE test may be used to diagnose Job syndrome. This syndrome is an inherited disease characterised by constantly high levels of IgE in the blood, recurrent infections, bone defects and eczema. The total IgE test is also sometimes useful in diagnosing multiple myeloma.
On the other hand, sometimes a total IgE test may fail to detect an allergy because of naturally lower than normal IgE levels in the blood of certain people. In these cases, a screening test may not be as helpful as an allergen-specific IgE test.
Allergen-Specific IgE Tests
Since the Total IgE test does not help in identifying the specific allergy and merely tells us of the presence or absence of it, an allergen-specific IgE test is much more useful in finding out the cause of allergy. This test makes use of IgE-specific immunoassay methods as well as the RAST test. Suspected allergens are grouped and introduced in this test to find the cause of allergy.
When the total IgE test is normal but the clinical picture strongly suggests an allergic reaction, it is highly recommended to perform allergen-specific IgE tests.
Usually, the symptoms of allergies are easily identifiable but even when there is a suspicion, it is best to check in with your doctor. The first-line treatment medications for allergies are anti-histamines. This group of drugs blocks the release of histamine from the IgE stimulated mast cells and basophils, thus reversing constriction of the bronchi, sneezing, running nose and watery eyes. Currently, second-generation antihistamines are preferred over the first generation because of the less sedating side effects and the longer duration of action.
Other drugs that are commonly prescribed to manage allergies are decongestants and sometimes, allergy shots. In fatal anaphylactic reactions, life-saving interventions and an epinephrine injection is given to save the patient from a respiratory collapse.
It is also recommended to minimise the exposure to the allergen as much as possible. If it is a food allergy you’re suffering from, the particular food should be completely excluded from the diet. If it is dust or pollen allergy, masks should be worn outside and dusty, overcrowded places should be avoided.
Why is Screening for Allergies Important?
The prevalence of allergy worldwide is high. Allergic rhinitis affects up to 30% of the population. Sensitization (IgE) antibodies to foreign proteins in the environment are present in 40% of individuals.
A total IgE screening test can quickly identify whether you have any allergies or a parasitic infection. Scheduled screening tests throughout the year are necessary to keep allergies in check and take quick action in managing them before they become a misery. Consult with your doctor as soon as you notice the slightest symptoms of an allergy for early treatment and recovery.
If you want to find out more about how you can diagnose your allergies, take a look at our lifestyle article here!
Interested in other biomarkers? Check out the rest of The Biomarker Handbook.
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