Innate and adaptive immunity

Question 1

2 stem cells populate the entire immune system, they divide into 2 linages, what are they?

Answer 1

• Those that give rise to cells which populate the innate immune system i.e. RBC and platelets
• The common lymphoid cells that give rise to the adaptive immune system

Question 2

Describe the specificity and memory of innate immunity

Answer 2

Non-specific and no memory

Question 3

Give some mechanical examples of innate immuntiy

Answer 3

1. Body surface: skin, fur - prevents pathogens from entering the system via the skin
2. Cilia in respiratory tract - traps pathogens and forces them out via exhalation
3. Flushing by liquids e.g. tears, urine, diarrhoea
4. Mucus as a barrier - over production when there is a pathogen

Question 4

Give 2 physiological changes of the innate immune system

Answer 4

• pH changes

- Pyrexia = fever/change in body temperatre

Question 5

Describe the structure and function of defensins

Answer 5

• Small 15-20aa proteins
• Found in many cells and tissues, they lack specificity
• Active against bacteria, fungi and viruses
• Bind to the microbe membrane
• Create a hole and disrupt the homeostasis of the pathogen as they cause a gradient between the internal and external environment
• Cause the dilution of essential molecules within the pathogen

Question 6

What is the function of lysozyme and sweat gland secretions?

Answer 6

Attack peptidoglycan walls of bacteria

Question 7

Describe how the myeloperoxidase system works

Answer 7

• Enzyme found mainly in lysosomes, granulocytes and macrophages
• Kills bacteria and other pathogens by production of toxic hypochlorite and a single oxygen
• Causes a fatal compromise in their redox system causing them to stop respiring

Question 8

Which molecule is used as an indicator for an inflammatory response?

Answer 8

Acute phase proteins

Question 9

How do macrophages function?

Answer 9

By ingesting (phagocytosis) and killing microorganisms

Question 10

How do neutrophils function?

Answer 10

• Phagocytosis

- Release of granules into the external environment

Question 11

How do Mast cells/Basophils/Eosinophils function?

Answer 11

• They have receptors for antibodies and increase vascular permeability
• Basophils and Eosinophils are also granulocytes

Question 12

What is the name given to bacteria in the gut that cause no harm?

Answer 12

Commensal bacteria

Question 13

How can commensal bacteria prevent other bacteria infections?

Answer 13

• Inhabit mucosal surfaces, especially in GI & respiratory tracts, and skin.
• Prevent attachment of pathogenic bacteria and hence block their invasion and infection.
• Competitive exclusion

Question 14

What effect do antibodies have on competitive exclusion?

Answer 14

• There will be a large colony of commensal bacteria
• Antibiotics kill many of these commensal bacteria
• This allows pathogenic bacteria to access tissues that were previously inhabited, causing infection

Question 15

Adaptive immunity is built from which 2 cells?

Answer 15

T and B cells

Question 16

What are the 3 defining features of adaptive immunity?

Answer 16

• Very specific
• Self/non-self discrimination (Distinguishing between the hosts own proteins and the proteins of the pathogen)
• Memory

Question 17

After the first challenge, when will acquired immunity peak?

Answer 17

About 2 weeks after

Question 18

Describe the rates of response of the innate and active immune systems upon the first challenege

Answer 18

Upon the 1st challenge the active immune system responds at a slower rate compared to the innate immune system

Question 19

What is generated by the adaptive immune system during the primary response?

Answer 19

Memory B-cells

Question 20

What are the 3 stages of action when defending against a microbial invasion?

Answer 20

1. Physical barriers
2. Innate immunity - inflammation, defensins, lysozyme
3. Adaptive immunity - antibody production, cell mediated immunity

Question 21

Provide a definition of an antigen

Answer 21

Is any molecule that can bind specifically to an antibody or antigen receptor.
Their name arises from their ability to generate antibodies

Question 22

Provide a definition of an epitope

Answer 22

Is a site on an antigen recognised by an antibody or antigen receptor.
They are short peptides derived from a protein antigen.
It can bind to an MHC molecule and is recognised by a particular T-cell

Question 23

Provide a definition of an antibody

Answer 23

Is a protein that binds to a particular substance - its antigen.
Each antibody has a unique structure that enables it to bind specifically to its antigen.
All antibodies have the same overall structure known as immunoglobulins.