What is the role of the immune system in allergies and anaphylaxis
There has been an accumulating evidence in the past decade on the physiological role of IgE: this isotype has co-evolved with basophils and mast cells in the defence against parasites love helminths (like Schistosoma) but may be also effective in bacterial infections. Epidemiological research shows that IgE level is increased when infected by Schistosoma mansoni,Necator americanus, and nematodes in humans. It is most likely beneficial in removal of hookworms from the lung.
Although it is not yet well understood, IgE may frolic an significant role in the immune system’s recognition of cancer, in which the stimulation of a strong cytotoxic response against cells displaying only little amounts of early cancer markers would be beneficial. If this were the case, anti-IgE treatments such as omalizumab (for allergies) might own some undesirable side effects. However, a recent study, which was performed based on pooled analysis using comprehensive data from 67 phase I to IV clinical trials of omalizumab in various indications, concluded that a causal relationship between omalizumab therapy and malignancy is unlikely.
Role in disease
Atopic individuals can own up to ten times the normal level of IgE in their blood (as do sufferers of hyper-IgE syndrome).
However, this may not be a requirement for symptoms to happen as has been seen in asthmatics with normal IgE levels in their blood—recent research has shown that IgE production can happen locally in the nasal mucosa.
IgE that can specifically recognise an allergen (typically this is a protein, such as dust miteDer p 1, cat Fel d 1, grass or ragweed pollen, etc.) has a unique long-lived interaction with its high-affinity receptor FcεRI so that basophils and mast cells, capable of mediating inflammatory reactions, become «primed», ready to release chemicals love histamine, leukotrienes, and certain interleukins.
These chemicals cause numerous of the symptoms we associate with allergy, such as airway constriction in asthma, local inflammation in eczema, increased mucus secretion in allergic rhinitis, and increased vascular permeability, it is presumed, to permit other immune cells to acquire access to tissues, but which can lead to a potentially fatal drop in blood pressure as in anaphylaxis.
IgE is known to be elevated in various autoimmune disorders such as Lupus(SLE), Rheumatoid Arthritis(RA) & psoriasis, and is theorized to be of pathogenetic importance in RA and SLE by eliciting a hypersensitivity reaction.
Regulation of IgE levels through control of B cell differentiation to antibody-secreting plasma cells is thought to involve the «low-affinity» receptor FcεRII, or CDCD23 may also permit facilitated antigen presentation, an IgE-dependent mechanism whereby B cells expressing CD23 are capable to present allergen to (and stimulate) specific T helper cells, causing the perpetuation of a Th2 response, one of the hallmarks of which is the production of more antibodies.
Role in diagnosis
Diagnosis of allergy is most often done by reviewing a person’s medical history and finding a positive result for the presence of allergen specific IgE when conducting a skin or blood test. Specific IgE testing is the proven test for allergy detection; evidence does not show that indiscriminate IgE testing or testing for immunoglobulin G (IgG) can support allergy diagnosis.
IgE primes the IgE-mediated allergic response by binding to Fc receptors found on the surface of mast cells and basophils.
Fc receptors are also found on eosinophils, monocytes, macrophages and platelets in humans. There are two types of Fcε receptors:
- FcεRI (type I Fcε receptor), the high-affinity IgE receptor
- FcεRII (type II Fcε receptor), also known as CD23, the low-affinity IgE receptor
IgE can upregulate the expression of both types of Fcε receptors. FcεRI is expressed on mast cells, basophils, and the antigen-presenting dendritic cells in both mice and humans. Binding of antigens to IgE already bound by the FcεRI on mast cells causes cross-linking of the bound IgE and the aggregation of the underlying FcεRI, leading to degranulation (the release of mediators from the cells) and the secretion of several types of type 2 cytokines love IL-3 and Stem Cell Factor (SCF) which both assist the mast cells survive and accumulate in tissue, IL-4, IL-5 and IL as well as IL which in turn activate group 2-innate lymphoid cells (ILC2, or natural helper cells).
Basophils, which share a common haemopoietic progenitor with mast cells, upon the cross-linking of their surface bound IgE by antigens, also release type 2 cytokines love interleukin-4 (IL-4) and interleukin (IL) and other inflammatory mediators. The low-affinity receptor (FcεRII) is always expressed on B cells; but IL-4 can induce its expression on the surfaces of macrophages, eosinophils, platelets, and some T cells .
What is the immune system?
The purpose of the immune system is to defend itself and hold microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body.
The immune system is made up of a complicated and vital network of cells and organs that protect the body from infection.
The organs involved with the immune system are called the lymphoid organs. They affect growth, development, and the release of lymphocytes (a type of white blood cell).
The blood vessels and lymphatic vessels are significant parts of the lymphoid organs. They carry the lymphocytes to and from diverse areas in the body. Each lymphoid organ plays a role in the production and activation of lymphocytes.
Lymphoid organs include:
Lymphatic vessels (a network of channels throughout the body that carries lymphocytes to the lymphoid organs and bloodstream)
Thymus (two lobes that join in front of the trachea behind the breast bone)
Peyer’s patches (lymphoid tissue in the little intestine)
Lymph nodes (small organs shaped love beans, which are located throughout the body and join via the lymphatic vessels)
Appendix (a little tube that is connected to the large intestine)
Adenoids (two glands located at the back of the nasal passages)
Blood vessels (the arteries, veins, and capillaries through which blood flows)
Spleen (a fist-sized organ located in the abdominal cavity)
Bone marrow (the soft, fatty tissue found in bone cavities)
Tonsils (two oval masses in the back of the throat)
IgE was simultaneously discovered in and by two independent groups:Kimishige Ishizaka and his wife Teruko Ishizaka at the Children’s Asthma Research Institute and Hospital in Denver, Colorado, and by S.G.O Johansson and Hans Bennich in Uppsala, Sweden. Their joint paper was published in April 
What is anaphylactic shock?
Anaphylactic shock, also called anaphylaxis, is a severe, life-threatening reaction to certain allergens.
Body tissues may swell, including tissues in the throat. Anaphylactic shock is also characterized by a sudden drop in blood pressure. The following are the most common symptoms of anaphylactic shock. However, each person may experience symptoms differently. Other symptoms may include:
Nausea, vomiting, or diarrhea
Loss of consciousness
Pain or cramps
Swelling of the throat and tongue or tightness in throat
Itching and hives over most of the body
Difficulty breathing or shortness of breath
Abnormal heart rate (too quick or too slow)
Anaphylactic shock can be caused by an allergic reaction to a drug, food, serum, insect venom, allergen extract, or chemical.
Some people who are aware of their allergic reactions or allergens carry an emergency anaphylaxis kit that contains injectable epinephrine (a drug that stimulates the adrenal glands and increases the rate and force of the heartbeat).
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Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) «isotype») that has only been found in mammals. IgE is synthesised by plasma cells.
Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε chain containing 4 Ig-like constant domains (Cε1-Cε4). IgE’s main function is immunity to parasites such as helminths love Schistosoma mansoni, Trichinella spiralis, and Fasciola hepatica. IgE is utilized during immune defense against certain protozoanparasites such as Plasmodium falciparum.
IgE also has an essential role in type I hypersensitivity, which manifests in various allergic diseases, such as allergic asthma, most types of sinusitis, allergic rhinitis, food allergies, and specific types of chronic urticaria and atopic dermatitis.
IgE also plays a pivotal role in responses to allergens, such as: anaphylactic drugs, bee stings, and antigen preparations used in desensitization immunotherapy.
Although IgE is typically the least abundant isotypeblood serum IgE levels in a normal («non-atopic») individual are only % of the Ig concentration, compared to 75% for the IgGs at 10mg/ml, which are the isotypes responsible for most of the classical adaptive immune responseit is capable of triggering the most powerful inflammatory reactions.
How does a person become allergic?
Allergens can be inhaled, ingested, or enter through the skin.
Common allergic reactions, such as hay fever, certain types of asthma, and hives are linked to an antibody produced by the body called immunoglobulin E (IgE). Each IgE antibody can be extremely specific, reacting against certain pollens and other allergens. In other words, a person can be allergic to one type of pollen, but not another. When a susceptible person is exposed to an allergen, the body starts producing a large quantity of similar IgE antibodies.
The next exposure to the same allergen may result in an allergic reaction. Symptoms of an allergic reaction will vary depending on the type and quantity of allergen encountered and the manner in which the body’s immune system reacts to that allergen.
Allergies can affect anyone, regardless of age, gender, race, or socioeconomic status. Generally, allergies are more common in children. However, a first-time occurrence can happen at any age, or recur after numerous years of remission.
Hormones, stress, smoke, perfume, or environmental irritants may also frolic a role in the development or severity of allergies.