Hypersensitivity Types II, III, and IV

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Questions and Answers

What is the main mechanism by which Type II hypersensitivity induces tissue damage?

T cells release cytokines that promote inflammation.

Plasma cells produce excess antibodies that target pathogens.

Antibodies bind to tissues and activate the complement system. (correct)

Neutrophils directly phagocytose the antigens.

In the context of frustrated phagocytosis, what happens to neutrophils when they bind IgG antibodies?

They successfully phagocytose the bound antigens.

They undergo apoptosis to prevent tissue damage.

They release granule contents causing inflammation. (correct)

They migrate away from the site of infection.

Which of the following substances is released by neutrophils during frustrated phagocytosis?

Cytokines

Antigens

Reactive oxygen species (ROS) (correct)

Complement proteins

What is a common result of antibodies binding to antigens on red blood cells in Type II hypersensitivity?

Destruction of the red blood cells Signup and view all the answers

What role do antibodies play in the complement system activation during Type II hypersensitivity?

They form complexes with antigens that trigger the complement pathway. Signup and view all the answers

What is the main characteristic of Type II hypersensitivity reactions?

Antibodies react with antigens on cell surfaces Signup and view all the answers

Which of the following best describes Type III hypersensitivity?

Due to immune complex formation Signup and view all the answers

What is the primary consequence of autoimmune hemolytic anemia?

Decreased number of RBCs Signup and view all the answers

What is a consequence of complement activation in Type II hypersensitivity?

Release of inflammatory mediators Signup and view all the answers

In Type III hypersensitivity, immune complexes are formed when antibodies bind to what?

Soluble antigens Signup and view all the answers

Which mechanism is primarily responsible for Type IV hypersensitivity reactions?

T cell-mediated delayed response Signup and view all the answers

What type of antibodies are typically involved in Type I hypersensitivity reactions?

IgE Signup and view all the answers

Which type of immune complex is most relevant in Type III hypersensitivity?

Very small immune complexes Signup and view all the answers

In terms of skin tests for hypersensitivity diagnosis, what does a positive result typically indicate?

Sensitivity to a specific antigen Signup and view all the answers

What is the role of complement activation in Type III hypersensitivity?

It recruits neutrophils and causes inflammation Signup and view all the answers

What role do autoantibodies play in Type II hypersensitivity reactions?

They target antigens on the surface of self-cells Signup and view all the answers

How do large immune complexes differ from small immune complexes regarding clearance from circulation?

Large complexes can be easily detected and removed Signup and view all the answers

What triggers the formation of the Membrane Attack Complex (MAC) in Type III hypersensitivity?

Complement activation by immune complexes Signup and view all the answers

Which of the following is true regarding the roles of antigens in Type II hypersensitivity?

Antigens are present on the cell surface or in circulation Signup and view all the answers

What is a common characteristic of soluble antigens that leads to immune complex formation?

They can provoke an antibody response Signup and view all the answers

What potential health issue arises from the deposition of immune complexes in blood vessels?

Vasculitis Signup and view all the answers

Which T cells are primarily involved in type IV hypersensitivity reactions?

Th1, Th17, and CD8+ T lymphocytes Signup and view all the answers

What is the main function of the cytokine IFN-γ produced by Th1 cells?

To activate macrophages Signup and view all the answers

What characterizes delayed-type hypersensitivity reactions?

They usually appear 24-48 hours after antigen challenge. Signup and view all the answers

In type IV hypersensitivity, which of the following would likely not be enhanced by macrophage activation?

Decreased cytolytic activity Signup and view all the answers

What is the role of Toll-like receptors (TLRs) in activated macrophages?

To enhance the ability to phagocytose Signup and view all the answers

Which type of cytokine profile characterizes Th1 cells?

Secretion of IFN-γ Signup and view all the answers

Which of the following statements is true regarding effector T-lymphocytes in delayed-type hypersensitivity?

They secrete cytokines several hours after arriving at the site. Signup and view all the answers

What is the significance of the MHC II expression increase in macrophages activated by Th1 cells?

It improves their capacity for antigen presentation. Signup and view all the answers

What is primarily responsible for guiding T cell migration to the site of infection?

Selectins and chemokine receptors Signup and view all the answers

Which of the following cytokines is NOT mentioned as playing a role in recruiting T cells?

IL-6 Signup and view all the answers

What changes occur in T cells upon activation and differentiation?

Reduction of CCR7 and increase of S1P receptor expression Signup and view all the answers

The movement of T cells from blood vessels into the tissue involves which of the following processes?

Rolling, adhesion, and transmigration Signup and view all the answers

What primarily causes the edema and fibrin deposition in areas of T cell infiltration?

Increased vascular permeability Signup and view all the answers

The role of chemokines at the site of infection includes which function?

Recruiting T cells to the area Signup and view all the answers

What type of cells infiltrate tissues during the immune response in addition to T cells?

Monocytes Signup and view all the answers

Which of the following statements is true regarding T cells and cytokines?

CD4+ T cells produce cytokines that guide T cell migration. Signup and view all the answers

Which of the following statements about superantigen-mediated diseases is true?

They can cause syndromes similar to septic shock. Signup and view all the answers

Which skin testing method is classified as immediate reaction tests?

Scratch test Signup and view all the answers

What is the primary risk associated with intradermal skin tests?

Risk of anaphylaxis Signup and view all the answers

What best describes the purpose of patch testing?

To determine photo-allergic reactions after UV exposure. Signup and view all the answers

How long should skin tests be performed after the resolution of allergic symptoms?

At least 3 weeks but not more than 3 months. Signup and view all the answers

Which of the following describes the skin prick test?

The safest and easiest method for skin testing. Signup and view all the answers

What is the main feature of the photopatch test?

The skin is irradiated with UV light post-patch removal. Signup and view all the answers

How is the skin scrape test performed?

By making a superficial scrape with a blunt tool. Signup and view all the answers

Study Notes

Hypersensitivity II Lecture Notes

Hypersensitivity is a complex topic with multiple types, including type I, II, III, and IV. This lecture focuses on hypersensitivity types II, III and IV.
Type II hypersensitivity reactions occur when antibodies bind to antigens on cells or tissues.
Antibodies, such as IgG and IgM, bind to "self" or "foreign" antigens on cells, causing various reactions.
Type II reactions lead to cell destruction by these reactions; antibody-mediated destruction of cells that may be part of the body's immune system or pathogens.
Type III hypersensitivity involves the formation of immune complexes that deposit in blood vessels.
These complexes activate complement and inflammatory cells, leading to tissue damage (inflammation) and vasculitis.
Common causes of type III hypersensitivity include infections, autoimmune diseases, and exposure to foreign antigens.
Type IV hypersensitivity is a T-cell mediated reaction that takes more than 12 hours to develop.
Type IV reactions result from T cell activation and the subsequent activation of macrophages, leading to tissue damage.
Learning Objectives for the lecture include Antibody-mediated andimmune complex disease (other than IgE). The mechanisms and clinical syndromes, as well as treatments for these reactions. Specific focus on type IV hypersensitivity, including mechanisms, clinical syndromes, and therapy; and principles of skin testing for the diagnosis of hypersensitivity reactions.

Learning Objectives hypersensitivity II

Antibody-mediated and immune complex diseases (other than IgE)
Their mechanisms, clinical syndromes, and treatments are key topics of interest.
Type IV hypersensitivity: mechanisms, clinical syndromes, and therapy will be covered.
Skin testing and its role in hypersensitivity diagnostics.

Types of hypersensitivity reactions in further detail

Type II hypersensitivity – Antibody-mediated reactions, where antibodies target specific antigens on cells/tissues.
Type III hypersensitivity – Immune complex mediated reaction, where antigen-antibody complexes deposit in blood vessels causing inflammation.
Type IV hypersensitivity – Cell-mediated reactions that take time (hours to days) to develop. Macrophage activation and T cell function are crucial for these reactions.

Testing for hypersensitivity

Skin tests are a common method for diagnosing hypersensitivity reactions. Common tests and descriptions are included.

Additional details

Autoimmune diseases: Certain autoimmune conditions are associated with specific types of hypersensitivity reactions.
Infections: Infections can also trigger hypersensitivity reactions.
Drugs: Some medications can cause hypersensitivity reactions.
Procedures: Specific steps for skin sensitization tests were highlighted.

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Description

This quiz reviews the complex topic of hypersensitivity, focusing specifically on types II, III, and IV reactions. You'll explore how antibodies and immune complexes lead to cellular destruction and inflammation, along with the common causes of these hypersensitivity reactions. Test your knowledge on this critical aspect of immunology.