Hypersensitivity Overview and Types
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Questions and Answers

What type of cells primarily process and present allergens during the sensitization phase of Type I hypersensitivity?

  • Macrophages
  • Dendritic cells (DC2) (correct)
  • B cells
  • T cells

Which cytokine is primarily involved in promoting the class switch to IgE in B cells during Type I hypersensitivity?

  • TNF-alpha
  • IL-5
  • IL-2
  • IL-4 (correct)

What is the outcome of the sensitization phase in a Type I hypersensitivity reaction?

  • Development of autoimmune disease
  • Inflammation at the site of allergen exposure
  • Animal is sensitized with no clinical signs (correct)
  • Immediate allergic reaction

Which type of T cells are preferentially elicited during the sensitization phase of Type I hypersensitivity?

<p>Th2 T cells (D)</p> Signup and view all the answers

What role do IgE antibodies play in Type I hypersensitivity after an allergen is encountered?

<p>They bind to Fc epsilon receptors on basophils and mast cells. (C)</p> Signup and view all the answers

What triggers the degranulation of mast cells in Hypersensitivity I?

<p>Re-exposure to an antigen (D)</p> Signup and view all the answers

What is the primary characteristic of hypersensitivity reactions?

<p>They are undesirable reactions produced by a normal immune response. (C)</p> Signup and view all the answers

Which of the following is NOT a vasoactive molecule contained in mast cell granules?

<p>Epinephrine (D)</p> Signup and view all the answers

In the context of an allergic response, what is the role of chemotactic molecules?

<p>To attract immune cells to the site of inflammation (B)</p> Signup and view all the answers

Which factors can lead to the development of hypersensitivity responses?

<p>Environmental antigens, microbes, and autoantigens. (C)</p> Signup and view all the answers

What is meant by sensitization in the context of hypersensitivity?

<p>The body's preparation for a second exposure to an antigen. (A)</p> Signup and view all the answers

What is a potential systemic effect of mast cell degranulation in an allergic response?

<p>Anaphylactic shock (D)</p> Signup and view all the answers

During the effector phase of Hypersensitivity I, which type of antibodies are primarily involved?

<p>IgE (A)</p> Signup and view all the answers

What are allergens defined as in the context of hypersensitivity?

<p>Substances that are harmless but provoke hypersensitivity. (B)</p> Signup and view all the answers

What can be inferred about the six-year-old cat's reaction after vaccination?

<p>It experienced an immediate allergic reaction despite prior vaccinations. (A)</p> Signup and view all the answers

What initiates the 'immediate hypersensitivity' response?

<p>Crosslinking of IgE on mast cells (A)</p> Signup and view all the answers

Which type of cell plays a critical role in the effector phase of Hypersensitivity I?

<p>Mast cells (C)</p> Signup and view all the answers

Why might a hypersensitivity reaction not occur after the first exposure to an antigen?

<p>The immune system may need previous sensitization before reacting. (B)</p> Signup and view all the answers

Which of the following is a characteristic of anaphylaxis?

<p>Massive release of mast cell mediators (D)</p> Signup and view all the answers

Which of the following best describes atopy?

<p>The genetic predisposition to develop allergic diseases. (B)</p> Signup and view all the answers

Which phase primarily involves the effector response in type I hypersensitivity?

<p>Immediate immune response phase. (C)</p> Signup and view all the answers

What role do amines like histamine play in the body during a hypersensitivity reaction?

<p>They induce smooth muscle contraction. (A)</p> Signup and view all the answers

What is the consequence of bronchial smooth muscle contraction during a hypersensitivity reaction?

<p>Constriction of the bronchi leading to suffocation. (B)</p> Signup and view all the answers

Which cells are primarily involved in the hypersensitivity response in the skin?

<p>Mast cells and keratinocytes. (D)</p> Signup and view all the answers

What is a result of mast cell degranulation during a hypersensitivity reaction?

<p>Release of histamine and inflammatory mediators. (D)</p> Signup and view all the answers

Which of the following can trigger Type I hypersensitivity reactions?

<p>Environmental allergens like pollen. (C)</p> Signup and view all the answers

What initiates the sensitization phase in Type II hypersensitivity related to drug-induced anemia?

<p>Hapten chemically bonding to cell surface proteins (A)</p> Signup and view all the answers

Which process is primarily responsible for the destruction of red blood cells in Type II hypersensitivity?

<p>Complement-dependent lysis (C)</p> Signup and view all the answers

In the context of hemolytic anemia of the newborn, how do maternal antibodies affect fetal red blood cells?

<p>They bind to fetal RBCs causing destruction (D)</p> Signup and view all the answers

What is a requirement for the mother to develop lethal antibody levels against fetal red blood cells in hemolytic disease?

<p>Multiple pregnancies with previous sensitization (B)</p> Signup and view all the answers

What is the role of IgG antibodies in Type II hypersensitivity during the effector phase?

<p>To activate complement and phagocytosis (C)</p> Signup and view all the answers

What is the main role of NK cells during the sensitization phase of viral infection?

<p>Releasing perforin and granzyme to lyse infected cells (A)</p> Signup and view all the answers

Which process is NOT part of the effector phase in response to infected cells?

<p>Directly activating helper T cells (C)</p> Signup and view all the answers

What is the significance of prior exposure in hypersensitivity reactions?

<p>It sensitizes the immune system without clinical signs initially. (B)</p> Signup and view all the answers

What type of antigens do the antibodies in hypersensitivity II primarily target?

<p>Self antigens or haptens attached to self proteins (D)</p> Signup and view all the answers

What is one of the mechanisms that the normal host defense utilizes against viral infections?

<p>Antibodies directed toward viral proteins on infected cells (C)</p> Signup and view all the answers

Flashcards

Hypersensitivity

An undesirable reaction from a normal immune response to an antigen, often not harmful, like food or pollen.

Sensitization

Initial exposure to an antigen, leading to an immune response that can cause hypersensitivity later.

Allergen

An antigen from an often harmless source, like food, drugs or pollen that can trigger an allergic reaction.

Atopy

A genetic predisposition to developing allergic diseases.

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Type I Hypersensitivity

A type of hypersensitivity reaction involving the release of chemicals.

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Type II Hypersensitivity

A type of hypersensitivity response where antibodies attack cells.

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Gell and Coombs Classification

A system for categorizing different types of hypersensitivity reactions.

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Hypersensitivity - Non-harmful exposure

A normal immune response to antigens that are typically not harmful to the body.

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Type I Hypersensitivity Sensitization

The initial stage of an allergic response where the body becomes sensitized to an allergen.

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Th2 Cells

A type of T cell that plays a crucial role in the allergic response by promoting IgE production.

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IgE

An antibody that plays a key role in allergic reactions by binding to mast cells and basophils.

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Mast Cells and Basophils

Immune cells that release histamine and other mediators during an allergic reaction.

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Mast Cell Degranulation

Mast cells release histamine and other chemicals in response to an allergen.

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Hypersensitivity Type I Effector Phase

The body's reaction to an allergen, leading to symptoms like bronchospasm and urticaria.

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Bronchial Smooth Muscle Contraction

Constriction of the airways in response to substances like histamine.

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Histamine

A chemical released by mast cells that causes inflammation and other allergic symptoms.

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Acute Inflammation

The localized tissue response (redness, swelling, etc.) to injury or irritation following the release of allergic mediators.

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Anaphylaxis

A life-threatening systemic allergic response characterized by the release of mast cell mediators throughout the body.

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Vasoactive Molecules

Chemicals released during an allergic response that affect blood vessels, causing them to dilate or constrict.

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Degranulation

The process by which mast cells release their granular contents (various chemicals) in response to an allergen.

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Drug-induced anemia

A type of anemia caused by a drug that modifies a cell surface protein, leading to an immune response against the modified cells.

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Hapten

A small molecule that doesn't trigger an immune response on its own but becomes antigenic when bound to a larger carrier molecule.

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Hemolytic anemia of the newborn

A type of anemia in newborns caused by maternal antibodies against fetal red blood cells.

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Opsonization

The process of coating a pathogen with antibodies or complement proteins to facilitate phagocytosis by immune cells.

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Complement-dependent lysis

A process where the complement system, a part of the innate immune system, forms a pore in the membrane of a target cell, leading to cell lysis.

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What is the sensitization phase of type II hypersensitivity?

The initial exposure to an antigen that triggers the immune system to create antibodies against it. This exposure does not cause any clinical signs, but sensitizes the body for future reactions.

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How do antibodies target cells in type II hypersensitivity?

Antibodies bind to the antigen on the surface of a cell. The antibody's constant region then binds to Fc receptors on immune cells like NK cells, PMN's, and Monocytes. This triggers the immune response.

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What are the effector mechanisms of type II hypersensitivity?

Once antibodies bind to antigen on cells, the body uses several mechanisms to get rid of the target cells. These include phagocytosis, complement-dependent lysis, agglutination and clearance, and antibody-dependent cell cytotoxicity.

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Why is type II hypersensitivity important for viral infections?

The same mechanisms used in type II hypersensitivity are crucial for fighting viral infections. Antibodies target viral proteins on infected cells, marking them for destruction by immune cells.

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What are the hallmarks of type II hypersensitivity?

Type II hypersensitivity requires prior exposure to the antigen, sensitizes the body without causing symptoms, and can target either self-antigens or chemicals bound to self-proteins. It's also a key part of normal immune defense against viral infections.

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Study Notes

Hypersensitivity Overview

  • Hypersensitivity is an undesirable reaction produced by a normal immune response, such as allergies and autoimmunity.
  • Hypersensitivity typically involves antigens that are not normally associated with harm, such as environmental antigens like food, pollen, fleas, or drugs.

Hypersensitivity Types

  • There are four main types of hypersensitivity reactions: Type I, Type II, Type III, and Type IV.
  • These types are categorized by the immune components involved and the effector phase or the time course.

Type I Hypersensitivity

  • Sensitization Phase: Initial exposure to an allergen doesn't cause immediate signs.
    • Antigen is processed and presented, resulting in the production of IgE antibodies.
    • IgE antibodies bind to mast cells and basophils, marking them for a subsequent response.
  • Effector Phase: Subsequent exposure to the allergen leads to rapid degranulation of mast cells and basophils.
    • Release of histamine, leukotrienes, and other mediators.
    • Causes inflammation and immediate hypersensitivity reaction.
  • Clinical Correlate: Examples include allergic rhinitis, asthma, and systemic anaphylaxis, in which there can be a sudden shock response from the massive release of mediators, such as with reaction to vaccines.
  • Location: Can occur in various locations, including the airways, gut, and skin.

Type II Hypersensitivity

  • Mechanism: Antibodies (IgG or IgM) bind to antigens on cell surfaces, causing cell damage or dysfunction through complement activation, phagocytosis, or antibody dependent cell-mediated cytotoxicity.
  • Examples: This includes blood transfusion reactions, hemolytic disease of the newborn, some autoimmune diseases, and some drug reactions.
  • Immune Components: Important components include antibodies and the complement system.
  • Drug-Induced Anemia: Exogenous chemical modifications of cell surface proteins, resulting in antibody production that targets these modified cells. This causes cell lysis and subsequent anemia.

Hypersensitivity Summary

  • Type I typically involves IgE and mast cells.
  • Type II typically involves IgG or IgM targeting and damaging cells or altered proteins.
  • Each type involves specific immune mechanisms, and results in a variety of clinical responses.
  • Immunotherapies can reduce immune responses associated with hypersensitivity.

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Description

Explore the different types of hypersensitivity reactions, from allergies to autoimmunity. This quiz will help you understand the mechanisms behind Type I, Type II, Type III, and Type IV hypersensitivity reactions, including the roles of IgE antibodies and mast cells. Test your knowledge on immune responses and their effects.

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