Hypersensitivity Reactions Practice Flashcards

Comprehensive vocabulary flashcards covering the definitions, types, mechanisms, and diagnostic evaluations of Hypersensitivity Reactions based on Chapters 25 and 20 of the lecture materials.

Hypersensitivity

A normal but exaggerated or uncontrolled immune response to an antigen that can produce inflammation, cell destruction, or tissue injury.

Immediate Hypersensitivity

An antibody-mediated immune reaction that occurs quickly after exposure to an antigen.

Delayed Hypersensitivity

A cell-mediated immune reaction that requires time after exposure to manifest.

Atopy

Immediate hypersensitivity mediated by $IgE$.

Allergens

Antigens that trigger allergic reactions via inhalation, ingestion, or inoculation.

Farmers Lung

A condition caused by an environmental inhalation of antigens prompting an $IgG$ response.

Type I Hypersensitivity

Antibody-mediated reaction, specifically involving $IgE$, ranging from mild food allergies to life-threatening anaphylaxis.

Type II Hypersensitivity

Cytotoxic-mediated reaction involving $IgM$ or $IgG$ antibodies against cell surface or extracellular matrix antigens.

Type III Hypersensitivity

Immune complex-mediated reaction caused by the deposition of circulating antigen-antibody complexes in vascular basement membranes.

Type IV Hypersensitivity

Cell-mediated reaction involving $CD4+$ and $CD8+$ T cells, also known as delayed hypersensitivity.

Mast Cells

Tissue basophils containing cellular receptors for $IgE$ that release mediators like histamine, heparin, and zinc ions upon allergen interaction.

IL-4

An inflammatory cytokine that activates and is secreted by $TH2$ cells and inhibits the development of $TH1$ and $TH17$.

IL-13

A cytokine produced by $TH2$ and lung epithelial cells that induces airway hypersensitivity.

Allergy March

A progression of allergic diseases in children that can begin as early as $2$ years of age.

Anaphylaxis

A dramatic and rapid generalized reaction characterized by vasodilation, smooth muscle constriction, and airway issues like bronchospasm.

Anaphylactoid Reaction

An anaphylaxis-like reaction to immunologically inert materials that act directly on mast cells or tissues without initial $IgE$ sensitization.

ImmunoCAP

The gold standard in vitro laboratory diagnostic test for hypersensitivity.

Desensitization (Hyposensitization)

A treatment involving allergy shots given at weekly intervals to produce excess $IgG$, which intercepts the allergen before it reaches $IgE$-bound cells.

Hemolytic Disease of the Newborn (HDFN)

A Type II hypersensitivity manifestation involving transplacental hemorrhage and antibody-dependent, complement-mediated cytotoxicity.

Cold Autoimmune Hemolytic Anemia

A condition characterized by cold agglutinins that react at room temperature or lower.

Warm Autoimmune Hemolytic Anemia

A condition involving $IgG$ antibodies that react at $37^\circ C$.

Complement Assays (C3 and C4)

Diagnostic tests used to evaluate Type III immune complex reactions.

PPD Skin Test

A diagnostic evaluation used for Type IV cell-mediated hypersensitivity, specifically for tuberculosis.

Contact Sensitivity

Allergic contact dermatitis, such as reactions to Poison Ivy, metals, or latex, classified as Type IV hypersensitivity.