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Immune system
Anaphylaxis
Asthma
Food allergy
Type I hypersensitivity
Autoimmune hemolytic anemia
Goodpasture syndrome
Graves disease
Hemolytic disease of the newborn
Myasthenia gravis
Pemphigus vulgaris
Rheumatic heart disease
Type II hypersensitivity
Poststreptococcal glomerulonephritis
Serum sickness
Systemic lupus erythematosus
Type III hypersensitivity
Contact dermatitis
Graft-versus-host disease
Type IV hypersensitivity
Asplenia
Common variable immunodeficiency
Hyperimmunoglobulin E syndrome
IgG subclass deficiency
Isolated primary immunoglobulin M deficiency
Selective immunoglobulin A deficiency
X-linked agammaglobulinemia
Adenosine deaminase deficiency
Ataxia-telangiectasia
Hyper IgM syndrome
Severe combined immunodeficiency
Wiskott-Aldrich syndrome
Complement deficiency
Hereditary angioedema
Cytomegalovirus infection after transplant (NORD)
Post-transplant lymphoproliferative disorders (NORD)
Chediak-Higashi syndrome
Chronic granulomatous disease
Leukocyte adhesion deficiency
Blood transfusion reactions and transplant rejection: Pathology review
Immunodeficiencies: Combined T-cell and B-cell disorders: Pathology review
Immunodeficiencies: Phagocyte and complement dysfunction: Pathology review
Immunodeficiencies: T-cell and B-cell disorders: Pathology review
Type I hypersensitivity
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type I hypersensitivity p. 110
type I hypersensitivity p. 110
type I hypersensitivity p. 110
type I hypersensitivity p. 110
type I hypersensitivity p. 110
IgE antibodies and p. 103
mast cells and p. 411
as type I hypersensitivity p. 111
Having a hypersensitivity means that someone’s immune system has reacted to something in such a way that it ends up damaging them, as opposed to protecting them.
There are four different types of hypersensitivities, and in the first type or type one, the reactions rely on Immunoglobulin E, or IgE antibody, which is a specific type of antibody - the other major ones being IgG, IgA, IgM, and IgD.
So because IgE is involved with type one hypersensitivity reactions they are also called IgE-mediated hypersensitivities.
This type of reaction is also sometimes called immediate hypersensitivities, because the reaction happens super fast—on the order of minutes.
So most allergic reactions are IgE-mediated, and therefore most allergies are type I hypersensitivity reactions.
“Allergy” comes from the Greek Allos which roughly means “other” and ergon which means “reactivity”.
Essentially, allergies are reactions to molecules from outside your own body that most people don’t react to—and these are specific molecules from things you might breathe or take in like foods, animal dander, bee stings, mold, drugs or medications, and pollen.
You can also mount an allergic reaction to things you come in contact with on your skin like latex, lotions, and soaps.
These specific molecules are also called antigens, and when they cause an allergic reaction, they’re called allergens.
An allergic reaction happens in two steps, a first exposure, or sensitization, and then a subsequent exposure, which is when it gets a lot more serious.
Type I hypersensitivity is a type of allergic reaction that occurs when the immune system overreacts to an otherwise harmless substance, such as pollen, dust, or certain foods. It is characterized by the rapid release of immunoglobulin E (IgE) antibodies in response to the allergen. In Type I hypersensitivity, the allergen triggers the production of IgE antibodies, which bind to specific receptors on mast cells and basophils in various tissues throughout the body. The next time the person is exposed to the same allergen, it triggers the release of histamine and other chemicals, causing the typical symptoms of an allergic reaction. Common examples of Type I hypersensitivity reactions include allergic rhinitis, asthma, hives, and anaphylaxis. Treatment options include avoiding the allergen, taking antihistamines and other medications, and in severe cases, using epinephrine to manage anaphylaxis.
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