Cellular Immunology: Chemotaxis and Receptors

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Questions and Answers

What is a likely consequence of a deficiency in early complement components?

Development of autoimmune diseases (correct)

Increased risk of allergic reactions

Enhanced production of antibodies

Heightened vaccine effectiveness

Which of the following proteins is stimulated by cytokines during an acute-phase response?

Immunoglobulin A (IgA)

Neuropeptide Y

C-reactive protein (CRP) (correct)

Insulin-like growth factor (IGF)

What is indicated by an elevated erythrocyte sedimentation rate (ESR)?

Deficiency in neutrophil production

Presence of severe bacterial infection

Normal inflammatory response

Indication of autoimmune diseases (correct)

Which immune response component has a specific deficiency leading to increased risk of infections with Neisseria species?

Membrane attack complex (MAC) Signup and view all the answers

What role do cytokines play in relation to body temperature during an immune response?

Increase body temperature and fat metabolism Signup and view all the answers

What role does Activated C3 play in the complement system?

Triggers the formation of the Membrane Attack Complex (MAC) Signup and view all the answers

Which components are involved in creating the pore that allows passage of water and solutes in the MAC?

C7, C8, and C9 Signup and view all the answers

What is the consequence of defects in early lectin and classical pathways of the complement system?

Type III hypersensitivity leading to immune complex disease Signup and view all the answers

How does CD59 (protectin) function within the complement system?

Inhibits the polymerization of C9 during MAC formation Signup and view all the answers

What cytokines do macrophages secrete during the acute phase response?

IL-1, IL-6, and TNF Signup and view all the answers

Which process is primarily affected by cytokines released during infections?

Activation of neutrophils for phagocytosis Signup and view all the answers

What constitutes the Membrane Attack Complex (MAC)?

C5 through C9 components of the complement system Signup and view all the answers

What is the effect of IL-1 and IL-6 cytokines on the immune system?

Activate phagocytic cells and the specific immune system Signup and view all the answers

What is the role of IgG in phagocytosis?

IgG acts as an opsonin, stimulating phagocytosis. Signup and view all the answers

Which of the following statements about C-lectin receptors is true?

C-lectin receptors activate macrophages leading to cytokine production. Signup and view all the answers

What is the primary function of receptors for complement components on phagocytes?

To bind pathogens that have been opsonized by complement proteins. Signup and view all the answers

Which type of receptors are involved in stimulating Toll-like receptor (TLR) pathways?

Drugs based on TLR ligands Signup and view all the answers

Which type of receptor helps phagocytes recognize apoptotic cells?

Receptors for apoptotic cells Signup and view all the answers

What effect do colony-stimulating factors (CSFs) have on the production of cells?

They enhance the production of neutrophils. Signup and view all the answers

What is the primary purpose of stimulating Toll-like receptors in the immune response?

To activate various components of the immune system. Signup and view all the answers

How do phagocytes utilize receptors for complement components in their immune function?

They bind to immune complexes and dead cells. Signup and view all the answers

What type of receptors allow phagocytes to enhance their migratory response towards inflamed tissues?

Chemokine and cytokine receptors Signup and view all the answers

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.