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Introduction to the immune system
MHC class I and MHC class II molecules
B-cell activation and differentiation
Cell-mediated immunity of CD4 cells
Cell-mediated immunity of natural killer and CD8 cells
Somatic hypermutation and affinity maturation
Contracting the immune response and peripheral tolerance
B- and T-cell memory
Anergy, exhaustion, and clonal deletion
Type I hypersensitivity
Type II hypersensitivity
Type III hypersensitivity
Type IV hypersensitivity
Innate immune system
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Hypersensitivity Type I
type I hypersensitivity p. 110
IgE antibodies and p. 103
mast cells and p. 409
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.
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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