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Questions and Answers
What do immune complexes trigger?
What is released by the activation of immune complexes?
What is the effect of histamine on blood vessels?
What is the primary location where antigen-antibody complexes become trapped?
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What attracts neutrophils to the site of inflammation?
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What is required for immune complexes to develop?
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What is a consequence of platelet aggregation?
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What is the typical time frame for the reaction to occur after exposure to the antigen?
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What forms in the blood as a result of antigen-antibody interactions?
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What is the primary mechanism for removing immune complexes?
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What is the result of the activation of the classical complement pathway?
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What is the final outcome of the immune complex-mediated tissue injury?
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What is the type of hypersensitivity reaction described in this chapter?
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What is the typical condition for immune complex formation?
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What is the result of immune complexes deposition in tissues?
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When do the largest immune complexes form?
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What type of antigens are produced from fungal spores?
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What is the optimal ratio between antigen and antibody for immune complex formation?
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What type of immunoglobulin molecules are mostly involved in immune complex formation?
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What happens when antibody levels exceed antigen levels?
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Where can immune complexes deposit in the body?
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What is an example of an autoantigen?
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What is the result of immune complex deposition in the glomerular basement membrane?
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What is the term for the deposition of immune complexes in synovial joints?
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What is an example of a clinical condition associated with Type III hypersensitivity?
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What is the main mechanism of Type IV hypersensitivity?
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What is a diagnostic test for immune complex-mediated hypersensitivity?
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What is the treatment for hypersensitivity reactions?
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What is an example of an autoimmune disease associated with Type III hypersensitivity?
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What is the term for the depletion of complement levels in serum?
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What is a common local reaction in diabetic patients receiving insulin subcutaneously?
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What is the formation of blood clots in small blood vessels leading to vascular occlusion?
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What is a systemic immune complex phenomenon?
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What are the symptoms of serum sickness 10 days after injection?
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What is an example of a treatment that can cause serum sickness?
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What is deposited in small blood vessels leading to vasculitis?
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What is the result of immune complexes deposited in small blood vessels?
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What is the name of the reaction that occurs when antigen is slowly cleared from circulation?
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Study Notes
Mechanism of Tissue Injury
- Immune complexes trigger inflammatory processes, activating the release of anaphylatoxins C3a, C5a, and stimulating degranulation of basophiles and mast cells, which release histamine.
- Histamine increases vascular permeability and helps deposit immune complexes.
Immune Complex Formation
- Large quantities of soluble antigen-antibody complexes form in the blood and are not completely removed by macrophages.
- These complexes lodge in blood vessels between endothelial cells and the basement membrane.
Steps of Type III Hypersensitivity
Step 1
- Large quantities of soluble antigen-antibody complexes form in the blood and are not completely removed by macrophages.
Step 2
- These antigen-antibody complexes lodge in blood vessels between endothelial cells and the basement membrane.
Step 3
- The antigen-antibody complexes activate the classical complement pathway, leading to vasodilation.
Step 4
- Complement proteins and antigen-antibody complexes attract leukocytes to the area.
Step 5
- Leukocytes discharge their killing agents, promoting massive inflammation, which can lead to tissue death and hemorrhage.
Type III Hypersensitivity
- Results from large quantities of soluble antigen-antibody complexes passing between endothelial cells of blood vessels and becoming trapped on the surrounding basement membrane.
- Immune complexes may form when antigen is present for a sufficient time to elicit an antibody response, usually when antigen is in slight excess of antibody.
Characteristics of Immune Complexes
- Form when the ratio between antigen and antibody is exactly right.
- Mostly consist of IgG and rarely IgM.
- Can deposit in tissues, causing tissue injury.
- May deposit in blood vessel walls (vasculitis), synovial joints (arthritis), and glomerular basement membrane (glomerulonephritis).
Clinical Conditions
- Arthus Reaction: local reactions in the form of erythema, edema, and necrosis.
- Serum Sickness: a systemic immune complex phenomenon resulting from injection of large doses of foreign serum.
- Post-streptococcal glomerulonephritis: glomerulitis associated with infective endocarditis.
- Hypersensitive pneumonitis (farmer lung): immune complexes deposit in the lung after repeated inhalation of dust or mold spores.
- Endogenous antigen-antibody complexes involved in autoimmune diseases, such as SLE and rheumatoid arthritis.
Diagnostic Tests
- Examination of tissue biopsies for deposits of immunoglobulins and complement by immunofluorescence.
- The presence of immune complexes in serum.
- Depletion in the level of complement.
Treatment
- Anti-inflammatory drugs.
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Description
This quiz covers the mechanism of tissue injury caused by immune complexes and the immune response, including the release of anaphylatoxins and histamine.
