COPY: Types of Immune Response: Hyperreactivity Types III & IV
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Questions and Answers

What is the primary mechanism underlying Type III hypersensitivity reactions?

It is mediated by IgG and IgM antibodies against soluble antigens, leading to the formation of immune complexes.

How does the timing of Type III hypersensitivity reaction differ from Type IV?

Type III reactions occur 3-8 hours after exposure, whereas Type IV reactions begin 24-72 hours later.

Identify a clinical example of a systemic disease associated with Type III hypersensitivity.

Serum sickness is a systemic disease caused by Type III hypersensitivity.

What characterizes the Arthus reaction in localized Type III hypersensitivity?

<p>The Arthus reaction is characterized by a localized immune response causing tissue necrosis at the injection site.</p> Signup and view all the answers

Describe the role of T lymphocytes in Type IV hypersensitivity reactions.

<p>T lymphocytes mediate the destruction of cells in Type IV hypersensitivity, often along with macrophages and cytokines.</p> Signup and view all the answers

What type of tissue injury is primarily observed in Type III hypersensitivity reactions?

<p>necrotizing vasculitis and fibrinoid necrosis are key features of tissue injury in Type III hypersensitivity.</p> Signup and view all the answers

Name a favored site for immune complex deposition in autoimmune diseases related to Type III hypersensitivity.

<p>Renal glomeruli are a favored site for immune complex deposition in autoimmune diseases.</p> Signup and view all the answers

What is the typical latency period associated with Type IV hypersensitivity reactions?

<p>Type IV hypersensitivity reactions typically have a latency period of 24 to 72 hours after antigen exposure.</p> Signup and view all the answers

Explain the inflammatory infiltrate observed in Type III hypersensitivity reactions.

<p>Inflammatory infiltrate typically includes neutrophils in tissues affected by Type III hypersensitivity.</p> Signup and view all the answers

What is one distinguishing feature that separates Type III and Type IV hypersensitivity reactions?

<p>One distinguishing feature is that Type III reactions involve soluble antigens and immune complexes, while Type IV reactions are mediated by T cells.</p> Signup and view all the answers

What distinguishes Type IV hypersensitivity from the other types?

<p>Type IV hypersensitivity is cell-mediated and involves a delayed reaction, unlike the antibody-mediated responses of the first three types.</p> Signup and view all the answers

What role do CD4+ T-helper cells play in Type IV hypersensitivity?

<p>CD4+ T-helper cells activate macrophages and release inflammatory mediators, leading to delayed hypersensitivity reactions.</p> Signup and view all the answers

Describe the Mantoux test and its significance.

<p>The Mantoux test involves injecting a mycobacterial antigen into the skin, resulting in a detectable reaction within 24 to 48 hours, indicating prior exposure to tuberculosis.</p> Signup and view all the answers

What is granuloma formation and why does it occur in Type IV hypersensitivity?

<p>Granuloma formation is the aggregation of epithelioid cells due to persistent intracellular antigens that stimulate T cells unable to eliminate the pathogen.</p> Signup and view all the answers

What are epithelioid cells and their characteristics?

<p>Epithelioid cells are transformed macrophages with abundant, large, and pink cytoplasm, resembling epithelial cells.</p> Signup and view all the answers

How do CD8+ T cells contribute to cell-mediated cytotoxic reactions?

<p>CD8+ T cells mediate cytotoxicity by inducing apoptosis in antigen-bearing cells.</p> Signup and view all the answers

Can you provide examples of conditions associated with CD8+ mediated cytotoxic reactions?

<p>Examples include cytotoxic reactions against virus-infected cells, transplant rejections, and Type 1 diabetes.</p> Signup and view all the answers

What leads to chronic graft-versus-host disease?

<p>Chronic graft-versus-host disease arises from the activation of T cells against host tissues post-transplant, leading to prolonged immune responses.</p> Signup and view all the answers

Explain the significance of allergic contact dermatitis in the context of Type IV hypersensitivity.

<p>Allergic contact dermatitis represents a specific type IV hypersensitivity reaction triggered by environmental chemicals causing skin inflammation.</p> Signup and view all the answers

What pathological changes are observed in the skin during allergic contact dermatitis?

<p>The skin shows epidermal necrosis, inflammation, rashes, and blisters during allergic contact dermatitis.</p> Signup and view all the answers

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