Questions and Answers
What is a likely consequence of a deficiency in early complement components?
Which of the following proteins is stimulated by cytokines during an acute-phase response?
What is indicated by an elevated erythrocyte sedimentation rate (ESR)?
Which immune response component has a specific deficiency leading to increased risk of infections with Neisseria species?
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What role do cytokines play in relation to body temperature during an immune response?
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What role does Activated C3 play in the complement system?
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Which components are involved in creating the pore that allows passage of water and solutes in the MAC?
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What is the consequence of defects in early lectin and classical pathways of the complement system?
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How does CD59 (protectin) function within the complement system?
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What cytokines do macrophages secrete during the acute phase response?
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Which process is primarily affected by cytokines released during infections?
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What constitutes the Membrane Attack Complex (MAC)?
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What is the effect of IL-1 and IL-6 cytokines on the immune system?
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What is the role of IgG in phagocytosis?
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Which of the following statements about C-lectin receptors is true?
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What is the primary function of receptors for complement components on phagocytes?
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Which type of receptors are involved in stimulating Toll-like receptor (TLR) pathways?
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Which type of receptor helps phagocytes recognize apoptotic cells?
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What effect do colony-stimulating factors (CSFs) have on the production of cells?
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What is the primary purpose of stimulating Toll-like receptors in the immune response?
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How do phagocytes utilize receptors for complement components in their immune function?
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What type of receptors allow phagocytes to enhance their migratory response towards inflamed tissues?
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Study Notes
Chemotaxis and Colony-Stimulating Factors
- Chemotaxis involves the directional migration of cells towards chemokine gradients in inflamed tissues.
- Colony-stimulating factors (CSFs), produced by tissue macrophages, stimulate the production of immune cells during acute-phase responses.
- Filgrastim, a recombinant granulocyte CSF, boosts neutrophil numbers, particularly after stem cell transplants.
Macrophage Receptors
- Phagocytes utilize various receptors to navigate tissues and interact with pathogens or damaged cells.
Receptors for Immunoglobulin
- Phagocytes recognize IgG via Fc receptors, which acts as opsonins to stimulate phagocytosis.
Receptors for Complement Components
- Phagocytes bind to pathogens opsonized by complement components like C3b.
- They also bind to immune complexes and dead cells.
Lectin Receptors
- Lectins are sugar-binding proteins; C-lectin receptors activate macrophages leading to cytokine production.
- C-lectin receptors capture pathogens and direct them to endocytic pathways.
Drugs Targeting Toll-Like Receptors
- Stimulating Toll-like receptors (TLRs) has strong activating effects on immune system components.
Receptors for Apoptotic Cells
- Phagocytes have receptors that recognize and bind to apoptotic cells, aiding in clearance and response.
Complement System Overview
- Activated C3 initiates the final phase of complement cascade, forming the membrane attack complex (MAC) with components C5 through C9.
- C5 and C6 possess enzymatic activity facilitating the integration of C7, C8, and C9 into target cell membranes.
- C9 molecules polymerize to form a ring, creating a pore that disrupts the plasma membrane, allowing solutes and water to enter, leading to cell death.
Acute Phase Response
- During infections, cytokines (IL-1, IL-6, TNF) released by macrophages activate the specific immune system.
- These cytokines increase body temperature (fever) and fat metabolism via hypothalamic effects.
- They stimulate liver synthesis of proteins:
- Innate immune molecules (C3, C4, CRP)
- Damage-limiting proteins (α1-antitrypsin, haptoglobin)
- Clotting factors (fibrinogen)
- Key characteristics of an acute-phase response include:
- Elevated neutrophil count
- Raised C-reactive protein (CRP) levels
- Increased erythrocyte sedimentation rate (ESR)
Clinical Implications of Complement Deficiencies
- Deficiencies in early lectin and classic complement pathways lead to type III hypersensitivity, impairing immune complex solubilization and phagocytosis.
- Early complement component deficiencies may contribute to autoimmune diseases, such as Systemic Lupus Erythematosus (SLE).
- Middle and late complement component deficiencies are associated with increased susceptibility to recurrent bacterial infections.
- Deficiencies in the MAC specifically increase the risk for infections caused by Neisseria species.
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Description
This quiz explores the concepts of chemotaxis and the role of colony-stimulating factors in the migration of immune cells. It also delves into the receptors on macrophages that facilitate phagocytosis. Test your understanding of these important immunological processes.
