Types of Immune Response

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Questions and Answers

What is the primary role of CD4+ T-helper cells in the context of delayed hypersensitivity reactions?

Activating B cells to produce antibodies

Enhancing the immediate hypersensitivity response

Releasing inflammatory mediators to activate macrophages (correct)

Mediating apoptosis in infected cells

What characterizes the tuberculin reaction observed in the Mantoux test?

It occurs immediately after antigen exposure

It involves activation of CD8+ T cells

It is a type of autoimmune reaction against self-antigens

It generates a detectable reaction within 24 to 48 hours (correct)

Which cytokine is primarily associated with the activation of macrophages in granuloma formation?

IFN-γ (correct)

IL-22

TNF-α

IL-6

Which statement about CD8+ T cells is correct?

They are responsible for stimulating apoptosis in virus-infected cells. (A) Signup and view all the answers

Which reaction is NOT classified as a delayed hypersensitivity reaction?

Cytotoxic response to a viral infection (A) Signup and view all the answers

What is the role of Th17 cells in the immune response?

They promote inflammatory reactions and recruit neutrophils. (C) Signup and view all the answers

Which of the following conditions is associated with the destruction of pancreatic islet cells?

Type-1 diabetes (D) Signup and view all the answers

Which agent is specifically known to trigger allergic contact dermatitis?

Poison ivy (C) Signup and view all the answers

What type of hypersensitivity reaction is characterized by the formation of granulomas?

Type IV (C) Signup and view all the answers

What typical response involves activation of macrophages and the production of IFN-γ in the context of intracellular pathogens?

Delayed-type hypersensitivity (A) Signup and view all the answers

What is the key difference between Type III and Type IV hypersensitivity reactions?

Type III is antibody-mediated whereas Type IV is cell-mediated. (B) Signup and view all the answers

Which immune response is characterized by the deposition of immune complexes in tissues?

Type III hypersensitivity reaction. (D) Signup and view all the answers

What is the typical timeframe for the onset of reactions in Type IV hypersensitivity?

Onset 24-72 hours post-exposure. (A) Signup and view all the answers

Which clinical condition is an example of a localized immune complex-mediated disease?

Arthus reaction. (C) Signup and view all the answers

What type of immune response involves T lymphocytes, macrophages, and cytokines?

Type IV hypersensitivity. (D) Signup and view all the answers

What is the main antibody type involved in systemic immune complex-mediated diseases?

IgG. (C) Signup and view all the answers

Which of the following is NOT a characteristic of Type IV hypersensitivity?

It involves antibody production. (D) Signup and view all the answers

What leads to the tissue injury seen in Type III hypersensitivity?

Immune complex deposition and subsequent inflammation. (C) Signup and view all the answers

Which immune response mechanism may be involved in vaccine reactions or graft rejections?

Type IV hypersensitivity. (B) Signup and view all the answers

What is a major clinical manifestation of serum sickness?

Acute glomerulonephritis. (B) Signup and view all the answers

Study Notes

Hypersensitivity reactions, types III and IV, are discussed.
Students will be able to distinguish the pathogenesis of these reactions and apply them to clinical conditions.
This includes autoimmune disease, granuloma, virus-infected cells and tumor cells, and graft rejection.

Type III Hypersensitivity

Mediated by IgG and IgM antibodies against soluble antigens, exogenous or endogenous.
Reaction time is 3-8 hours after antigen exposure.
Reaction can be localized or systemic.
Antigen binds to antibody, forming immune complexes.
Circulating complexes deposit in postcapillary venules.
Complement fixation leads to leukocyte recruitment.
Inflammatory reaction, necrotizing vasculitis, and tissue injury occur.
Clinical example: Systemic immune complex-mediated disease (e.g., serum sickness), which follows foreign serum injection and causes symptoms like fever and vasculitis.
Clinical example: Localized immune complex-mediated diseases (e.g., Arthus reaction), a localized immune reaction in the skin after antigen injection in sensitized individuals.

Type IV Hypersensitivity

Also known as cell-mediated or delayed-type hypersensitivity.
T lymphocyte-mediated destruction of cells.
Reaction time is 24-48 hours after contact with an antigen.
CD4+ T-helper cells, and the release of inflammatory mediators (e.g., IFN-γ) cause problems.
Clinical example: Tuberculin reaction (Mantoux test): Mycobacterial antigen injection elicits a detectable skin reaction within 24-48 hours.
Clinical example: Granuloma formation: against non-degradable antigens like mycobacteria in tuberculosis.
Clinical example: Reaction to fungal infections by Th17 cells
Clinical example: Allergic contact dermatitis, due to reaction against poison ivy).

CD8+ Cell-mediated Cytotoxic Reaction

Mediated by CD8+ T cells.
Activated cytotoxic cells induce apoptosis in antigen-bearing cells.
Examples: Cytotoxic reactions against virus-infected and malignant cells
Type-1 diabetes: Pancreatic islet cell destruction and resulting insulin deficiency.
Examples: Graft-versus-host disease, and chronic transplant rejection.
Examples: Drug reactions, tattoo, black henna, nickel and bracelet allergies.

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Description

This quiz explores types III and IV hypersensitivity reactions, focusing on their pathogenesis and clinical applications. Students will learn to differentiate between autoimmune diseases, granulomas, and the effects of these responses on virus-infected cells and graft rejection.

Types of Immune Response - Hypersensitivities

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