Allergy Mechanisms and Type I Hypersensitivity

An abnormal immune response that can cause harm to the body, occurring only in sensitized individuals who have been previously exposed to the allergen.

A substance that causes an allergic reaction, typically a small protein with protease activity.

The process by which the immune system becomes sensitized to an allergen. This involves initial exposure and development of antibodies.

A type of immune response characterized by the release of histamine and other inflammatory mediators, leading to immediate allergic reactions.

A distinct type of CD4+ T cell that plays a crucial role in humoral immune responses, particularly against extracellular parasites and bacterial infections.

A predisposition to developing IgE-mediated allergic reactions.

A term that refers to swelling around the eyes.

A term that refers to swelling of the lips.

The late phase of an allergic reaction, occurring 2-24 hours after exposure, characterized by leukocyte migration (mainly eosinophils) and the release of substances like peroxidases causing further tissue damage.

Drugs that block the action of histamine, a chemical released during allergic reactions.

Antihistamines that target H1 receptors, found in various locations like smooth muscle, vascular endothelial cells, and the CNS.

First-generation H1 antihistamines have more central effects and are often used as sedatives, while second-generation H1 antihistamines have less central effect and are more commonly used for allergic reactions.

Antihistamines that target H2 receptors, primarily found in the stomach, and are used to reduce gastric acid production.

Drugs like corticosteroids that have a broad range of effects, including anti-inflammatory, immunosuppressive, and endocrine effects.

The ability of glucocorticoids to reduce inflammation, suppress the immune system, and affect hormones and metabolism.

The potential adverse effects of glucocorticoids, such as increased risk of infections, bone thinning, and hyperglycemia.

A type of immune cell that presents antigens to T cells, initiating an immune response.

A specific type of T helper cell that plays a crucial role in allergic reactions. It is activated by the binding of allergens to IgE receptors on mast cells.

An antibody that specifically binds to allergens and triggers the release of inflammatory mediators by mast cells, leading to allergy symptoms.

A type of immune cell that contains granules filled with inflammatory mediators, such as histamine. These cells are activated by allergens bound to IgE receptors on their surface, triggering the release of these mediators.

The process by which mast cells release their granules containing inflammatory mediators, such as histamine, upon activation by allergens.

A chemical mediator released by mast cells that causes smooth muscle contraction, vasodilation, and increased vascular permeability, leading to the characteristic symptoms of allergies.

A group of lipids that are involved in allergic reactions. One type, leukotriene C4 and D4, causes strong smooth muscle contraction in airways, contributing to breathing difficulties.

A type of prostaglandin that contributes to allergic reactions by causing bronchospasms, increased vascular permeability, and vasodilation.

Glucocorticoids have an immediate effect on vasodilation, but their main anti-inflammatory and immunosuppressive actions involve binding to glucocorticoid receptors and altering gene transcription.

Glucocorticoids are used for hormone replacement in conditions like Addison's disease, for managing both acute and chronic inflammation (e.g., rheumatoid arthritis), and for suppressing the immune system.

Glucocorticoids can be applied locally to treat skin conditions (dermatoses) and asthma.

Glucocorticoids can be applied topically, injected locally, inhaled, taken orally, or administered via injection (intramuscular, subcutaneous, intravenous).

Glucocorticoids cause a decrease in vasodilation and capillary permeability, leading to reduced fluid leakage and swelling at the site of inflammation.

Glucocorticoids inhibit the migration of leukocytes (white blood cells) to inflammatory sites, reducing the inflammatory response.

Glucocorticoids promote apoptosis (programmed cell death) in eosinophils, monocytes, and lymphocytes, reducing their numbers in the inflammatory environment.

Glucocorticoids inhibit the production of arachidonic acid derivatives, which are mediators of hypersensitivity reactions, by blocking phospholipase A2.

A process where T cells in the thymus are eliminated if they strongly bind to self-antigens presented by MHC molecules, ensuring that the immune system doesn't attack the body's own cells.

Antibodies that mistakenly target the body's own tissues or cells. They can cause autoimmune disorders by damaging healthy cells.

The mechanism that describes how an infectious agent might share similar amino acid sequences with self-antigens, leading to the immune system attacking the body's own cells. This occurs when antibodies or T cells mistakenly attack self-antigens because they recognize them as foreign.

In the context of autoimmunity, these are proteins normally hidden from the immune system that become exposed after tissue damage or stress, triggering the immune response against them. The immune system recognizes these exposed proteins incorrectly, leading to autoimmune reactions.

The predisposition for developing autoimmune disorders due to genetic factors. Some genes can increase the risk of developing certain autoimmune diseases.

The process by which the immune system reacts to an antigen it has encountered previously. Subsequent exposures to the same antigen trigger a faster and stronger immune response.

The ability of the immune system to distinguish between self-antigens (belonging to the body) and non-self antigens (foreign). This helps prevent autoimmunity.

Proteins produced by microorganisms (bacteria, mycoplasma, or virus-infected cells) that bind to T cell receptors without regard for specific antigens. They stimulate a large number of T lymphocytes, acting as potent immune-stimulating molecules.

The phenomenon where the enhanced processing and presentation of self-antigens by immune cells leads to the expansion of the immune response towards different self-antigens. This contributes to diseases like systemic autoimmune diseases.

The process of bystander action can lead to the immune system targeting other parts of the body. This process is called epitope spreading.

Autoimmune diseases develop when the immune system mistakenly attacks the body's own tissues and organs. This can involve multiple organs or systems, leading to various signs and symptoms.

Autoimmune diseases are thought to arise from a combination of genetic predisposition and environmental triggers. These triggers could include infections, chemical exposure, or hormonal imbalances.

Autoimmune diseases affect different organs and systems, leading to a wide range of symptoms. These symptoms can be systemic, affecting multiple parts of the body.

Autoimmune diseases can be challenging to diagnose due to their non-specific symptoms and the presence of multiple autoantibodies. The diagnosis often involves identifying the specific organ or system affected and the presence of associated antibodies.

Some autoimmune diseases primarily affect a single organ, such as the thyroid, making diagnosis easier. These are termed organ-specific autoimmune diseases.