11 Questions
What is the primary function of the Membrane Attack Complex (MAC)?
Destroying pathogens by forming a membrane-bound channel
Which of the following molecules is NOT involved in attracting cells to the site of infection?
C3b
What is the primary function of dendritic cells in the immune response?
Presenting antigens to T-cells
Which cells are activated by C3a and C5a to undergo degranulation?
Eosinophils and mast cells
What is the primary mechanism by which macrophages recognize pathogens and activate the innate immune system?
Pattern recognition receptors
What is the consequence of cytokines initiating an inflammatory response?
Vasodilation and increased vascular permeability
Which of the following cytokines is responsible for simulating the liver to produce acute phase proteins?
IL-6
What is the function of natural killer cells in the immune response?
To kill virally infected cells and tumour cells
What is the consequence of interferons inhibiting viral entry and replication?
Prevention of infection
What is the role of monocytes in the immune response?
To be recruited and become macrophages
What is the consequence of IL-1 being released during the acute phase response?
Fever, lethargy, and anorexia
Study Notes
Complement System Activation
- The complement system is activated by the presence of pathogens, leading to the destruction of the pathogen through the formation of the Membrane Attack Complex.
- C3b, a product of the complement system, acts as an opsonin, marking pathogens for destruction by immune cells.
Chemotaxis and Cell Activation
- C5a, a complement system component, attracts immune cells, including neutrophils, monocytes, and eosinophils, to the site of infection.
- C3a, C4a, and C5a activate mast cell degranulation, releasing histamine and other mediators.
- C3a and C5a also activate eosinophil degranulation, contributing to the inflammatory response.
Innate Immune System Activation
- Macrophages recognize pathogens and activate the innate immune system, triggering a rapid response to infection.
- Dendritic cells, upon recognizing pathogens, pick up antigens and migrate to activate the specific immune system, leading to a targeted response to infection.
Macrophage Activation
- Macrophages recognise pathogens and initiate phagocytosis
- Release cytokines and interferons as immune responses
- Interferons inhibit viral entry and replication within cells
Cytokine Functions
- Cytokines recruit help by activating monocytes to become macrophages
- Cytokines initiate an inflammatory response, leading to:
- Vasodilation
- Increased vascular permeability
- Localised endothelial cell activation
- Cytokines activate other systems, including:
- Mast-cell degranulation
- Clotting system activation
- Kinin system
Inflammatory Response and Acute Phase Response
- Inflammation leads to an acute phase response, characterised by:
- Macrophages and neutrophils secreting more cytokines, including interleukins
- Interleukins have various functions, including:
- IL-1: causing fever, lethargy, and anorexia
- IL-6: stimulating the liver to produce acute phase proteins (opsonins)
- IL-8: recruiting and activating neutrophils
- IL-2 and IL-12: activating natural killer cells
Natural Killer Cells
- Natural killer cells are recruited to tissues and:
- Kill virally infected cells (and tumour cells)
- Produce interferon-gamma (IFN-γ) that further stimulates macrophages
Learn about the complement system, a part of the innate immune system that helps eliminate pathogens. Understand how it activates and destroys pathogens, and its role in immune response.
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