Innate and Adaptive Immunity (Path)

Question 1

Define Antigen

Answer 1

a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies

it is any molecules that can bind specifically to an antibody or antigen receptor

Question 2

Define epitope

Answer 2

Part of the antigen that is recognized by an antibody or an antigen receptor
Short peptides

Can bind to an MHC molecule and (T cell epitopes) are recognised by a particular T cell.

B-cell epitopes are antigenic determinants recognized by B cells.

Question 3

Define antibody

Answer 3

a protein that binds specifically to its corresponding antigen

Known collectively as immunoglobulins

Question 4

Talk broadly about the cells of the immune system

Answer 4

There are 2 stem cells populate the entire immune system

Split into 2 lineages:

1. 1 stem cell that gives rise to moyloid cells that compose the innate systems
2. 1 stem cell that gives rise to adaptive cells: adaptive immune system

Question 5

Compare the cells that make up the adaptive and innate immune systems broadly

What is another huge contrast between the 2

Answer 5

Innate - far greater variety and number of cells than adaptive

Adaptive differentiation and specification occurs later in gestation/ post birth

Adaptive: B cell, T cell and NK cell

Innate: RBC, platelets, neutrophils, eosinophils, basophils and monocytes which give rise to macrophages

Innate immunit level of protection peaks after 30 mins whereas adaptive peaks after 2 weeks

Question 6

What are we focused on when comparing the 2 immune systems?

Answer 6

• Speed at which things occur between adaptive and innate
• Memory or capacity to remember
• Specificity

Question 7

What is the innate immune system?

Answer 7

No specific immune response we have from birth (is innate) - indiscriminate in what it will attack
• First line of defence in any animal

Question 8

What makes up the innate immune system?

Answer 8

• Mechanical
• Physiological
• Molecular/Cellular
• Microbiological & Environmental

Question 9

Talk about mechanical innate immune system

Answer 9

• Body surface: skin, fur, hair, feathers
• Cilia in respiratory tract - Pathogens trapped within cilia, can often be exhaled or forces OUT
• Flushing by liquids e.g mucous, tears (antimicrobial peptides), urine, diarrhoea
• Mucus - continually produced and overproduced if infection = why mucous out of nasopharynx is indicative of respiratory disease

Question 10

Talk about physiological innate immune system

Answer 10

• pH changes and extremes (e.g. Intestinal system)
• can damage membrane of bacteria/ virus, helminth, compromising pathogens homeostasis
• Pyrexia kills some infectious agents

Question 11

What comes under cellular innate defences in the innate immune system?

Answer 11

Macrophages
Neutrophils
Eosinophils
Basophils
Platelets
Molecular defences
Lysozymes
Microbiological defense

Question 12

How do macrophages and neutrophils respond in innate immunity

Answer 12

Macro - function by ingesting (phagocytosis) and killing microorganisms (lysosomes)

Neutrophils - phagocytic & degranulate (release granules into the external environment

Question 13

How do Mast cells/ basophils/ eosinophils respond in innate immunity

Answer 13

have receptors for antibodies and increase vascular permeability
They are granular and contain enzymes and active biological substances that are released (degranulation into the ECM
e.g. basophils release histamines
• See swelling – inc vascular permeability
• Heat
• Reddening
• Slight pain sensation

Question 14

Talk about defensins

Answer 14

1. part of innate immune response
2. small proteins
3. Found in many tissues and cells
4. Active against bacteria, fungi and viruses
5. Important in skin barrier to infections - at a mucosal surface or junction between the inside and outside, we will nearly always see defensins.
6. Create a pore in bacteria so they can no longer control movement across own membranes.
7. Bacteria lose capacity to function when gradient lost – cause dilution of essential molecules from inside the bacteria, fungus

Question 15

Talk about lysozymes

Answer 15

Part of the innate immune response
1. Family of enzymes which attack peptidoglycan cell walls of bacteria and worms
There are several sites of action including
- cellular e.g. Breaks down cell wall, stopping bacteria from being able to function properly and maintain homeostasis

Question 16

What is myeloperoxidase

Answer 16

• Enzyme found mainly in lysosomes in granulocytes and macrophages – produces hypochlorite (OCl- which is very useful as a disinfectant in labs) essentially a form of bleach
• Kills bacteria and other pathogens by production of toxic hypochlorite (OCl-) and singlet oxygen (1O2).

Question 17

Talk about microbiological defence

Answer 17

Commensal bacteria - flora and fauns

• Competitive exclusion.
Across intestinal tract we have millllions of bacteria and yeast that exist there but don’t do any harm – give benefit.
• By occupying space they prevent colonisation of pathogen that would want to occupy a space.
• Inhabit mucosal surfaces, especially in GI & respiratory tracts, and skin.
• Prevent attachment of pathogenic bacteria and hence block their invasion and infection – competitive exclusion = take up the physical space that the bacteria would.

Question 18

Talk about the importance of commensal bacteria on mucosal surfaces and why we aren’t so willing at giving antibiotics

Answer 18

• Come to influence use of antibiotics
• Not given so willingly more because as well as killing pathogens, they’re bound to have an impact on commensal bacteria
• Give antibiotics to relatively healthy person  within gut commensals of intestine (pink) are wipes out.
• So if come into contact with clostridium, then very quickly an infection is able to take hold

Question 19

Environmental/ management effect on innate immunity

Answer 19

• Husbandry – huge role
• Diet – balances essential to have properly function innate immune system
• Temperature/humidity – especially around respiratory mucosal surfaces. Cilia don’t work is too dry
• Form of immunodeficiency (later lecture)
Colostrum is gold!

Innate system is non specific. Has NO memory

Question 20

Adaptive immunity:

What cells and defining features

Answer 20

1. built from 2 (3) cells, T cells, B cells and natural killer cells
2. Defining features:
   • Specificity – a single T will respond ONLY to a single epitope.
   • Self / non-self discrimination – animals own proteins and proteins produced by animal
   • Memory – blue pic below. All consuming nucleus, occasionally see small slice of cytoplasm. Size is an indicator on whether been activated or not

Question 21

Adaptive immunity features

Answer 21

Specificity, Memory & Amplification

Question 22

invading microorganism, what are the 3 stages it faces with regards to immune response…

Answer 22

1. physical barrier - skin, self cleaning, normal flora
2. Innate immunity - inflammation, defensins, lysozymes
3. Specific immunity - antibody production, cell mediated immunity

Question 23

Differences between innate and adaptive immunity…

a) speed
b) specificity
c) MEmory

Answer 23

Innate

a) speed - quick
b) specificity - less
c) MEmory - none

Adaptive

a) speed - slow
b) specificity - high
c) MEmory -lots