Module 3, Lecture 4: Immune Function in Vertebrates Flashcards
Innate immunity
Present in all animals, it provides a fast response by recognizing common pathogen traits using a small set of receptors
Innate immunity – defences
Includes barrier defences and internal defences
Barrier defences
- Skin
- Mucous membranes
- Secretions
Internal defences
- Phagocytic cells
- Natural killer cells
- Antimicrobial proteins
- Inflammatory response
Adaptive (acquired) immunity
Only in vertebrates, it’s slower but recognizes specific pathogens using many receptors
Adaptive immunity – responses
Uses humeral response and cell-mediated response
Humoral response
Antibodies defend against infection in body fluids
Cell-mediated response
Cytotoxic cells defend against infection in body cells
Inflammatory response
Changes triggered by signalling molecules released after injury or infection
Histamine
inflammatory signalling molecule stored in mast cells
Innate immune system – Step 1: Signal release
Mast cells release histamine and macrophages release cytokines at the injury site
Innate immune system – Step 2: Capillary response
Histamine and cytokines cause capillaries to dilate and become permeable, letting fluid and antimicrobial peptides enter
Innate immune system – Step 3: Immune cell action
Neutrophils are attracted to the site, where they digest pathogens and debris, leading to tissue healing
Why are innate defenses insufficient?
They respond quickly but can’t adapt to new or changing pathogens, which can evolve to evade them
Limitations of the innate immune defense
- Nonspecific
- Has no memory
- limited strength
- needs backup
- Can be evaded by pathogens
Antigenic drift
Small, gradual genetic changes in pathogens that help them avoid immune detection
Antigenic shift
A sudden, major genetic change in a pathogen that creates a new strain unrecognized by the immune system
Zoonotic disease
A disease that can transfer from animals to humans
Influenza A (IAV)
- Undergoes antigenic drift and shift
- causes epidemics and pandemic
- circulates in humans, birds, and pigs
Influenza B (IBV)
- Only undergoes antigenic drift
- Causes epidemics but not pandemics
- circulates only in humans
What was unusual about influenza A?
the highest death rates were in 25–30-year-olds
