Review of the innate immune system Flashcards
What does a resolution of infection require?
• Resolution of infection requires both adaptive and innate immune responses
What does adaptive immunity involve?
Involves very specific recognition of infectious agent (usually sees a protein = antigen)
What is there no specific recognition in innate immunity and what does it involve?
• Innate immunity – no specific antigen recognition
§ Innate involves recognition of broadly conserved features of different classes of pathogens
What are the components of the innate immune system?
• Phagocytosis
• The Inflammatory Response
• Cytokines, Interferons and Antimicrobial peptides (AMPs)
• Complement
○ Enhances ability of immune system to work
• Intrinsic Defences – “the hostile cell”
• NK cells
What is phagocytosis carried out by in vertebrates?
Carried out in vertebrates by dendritic cells, macrophages and neutrophils
What are macrophages never involved in?
○ Macrophages are never involved in triggering new immune response but can reactivate memory
Where are macrophages found?
Macrophages are tissue-resident
What cells do most of the phagocytosing?
Neutrophils do most of the phagocytosing
What does phagocytosis clear and present and what does this promote?
• Phagocytosis clears pathogens but also presents peptides on MHCs – this promotes development or reactivation of the adaptive immune response
§ Selects and stimulates division of naïve T and B cells
What are the 2 distinct roles of macrophages in innate immunity?
- Phagocytosis; material is destroyed in lysosomes
2. Captured material can trigger macrophage activation
What do activated macrophages produce and what does this trigger?
○ Activated macrophages produce cytokines and chemokines to stimulate both innate and adaptive immune responses
§ This triggers the inflammatory response and can promote a local anti-microbial state
What is the inflammatory response?
A generic defence mechanism whose purpose is to localize and eliminate injurious agents and to remove damaged tissue components
What does the inflammatory response localise?
Localizes the infection
What does the inflammatory response remove and repair?
- Removes infectious agent i.e. by phagocytosis
* Repairs tissue damage
What does the inflammatory response enhance?
Enhanced permeability, extravasation, cell adhesion and clotting
What does the inflammatory response recruit?
• Neutrophil recruitment
What are cytokines and chemokines?
Glycoprotein hormones that affect the immune response
What do cytokines act as?
○ Act as a very specific signal for a component of the immune system
What does the role of cytokines help?
○ Very defined narrow role that helps the immune system
What do cytokines act to modify?
○ Act to modify the behaviour of cells in the immune response
What are most of the cytokines called?
○ Most of these are called interleukins (eg. IL-1)
Where are chemokines secreted?
○ Secreted at site of infection
What do chemokines act as and create?
○ Act as chemotactic factors
§ Create concentration gradients which attract (or occasionally repel) specific cell types to a site of production/infection
How do pathogens recognise material to ingest?
○ By detecting phosphatidylserine on exterior membrane surface (cells undergoing apoptosis)
○ By Scavenger receptors
○ By some Toll-Like Receptors (TLRs)
○ By passive sampling
