1. Basic concepts of animal immunology

Question 1

What is the goal of immunity?

Answer 1

The goal of immunity is to help return the body to a state of homeostasis

Question 2

Broadly, how does the immune system help achieve the goal of returning the body to a state of homeostasis?

Answer 2

Defending the host, cleaning up debri/spent cells, and controlling tissue damage

Question 3

What are 3 examples of different innate and adaptive mechanisms? Are they mutually exclusive?

Answer 3

1. Local vs. systemic
2. Innate vs. adaptive
3. Humoral vs. cell-mediated

*These terms are NOT mutually exclusive; high level of complementarity btw these immune tools

Question 4

What are strong drivers for evolution of immune defense mechanisms?

Answer 4

Host-pathogen interactions
- continue to shape novel pathogen infection strategies and host mechanisms that can overcome these developing infections

Question 5

For invading microbes, what has been the challenge in terms of evolution of host-pathogen interactions?

Answer 5

The challenge has been to devise clever evasion strategies that overcome immune defense mechanisms and increase the potential for survival and spread
- Can take advantage of mechanisms of antigenic variation, introduction of escape mutations, expression of immune suppressor genes, or several other potential mechanisms

Question 6

For the animal host, what has been the challenge in terms of evolution of host-pathogen interactions?

Answer 6

The challenge has been to develop mechanisms that will protect host by destroying infectious microbes and neutralizing their virulence factors
- the ultimate goal is to avoid death from infection

Question 7

How does the animal host achieve its ultimate goal of avoiding death from infection?

Answer 7

Via a highly integrated multilayer immune strategy that systematically targets incoming pathogens to prevent their spread throughout the host and minimize the potential for their transmission to other hosts

Question 8

Functional redundancy

Answer 8

Capacity of immune tools to exert similar and overlapping fxns on specific cells to provide extra safeguards if one layer of the system were to fail or be overcome by pathogen invasion strategies
- 2 mechanisms trying to do the same thing

Question 9

Functional pleiotropy

Answer 9

Capacity of immune tools to exhibit a wide variety of biological fxns on various tissues and cells
- opposite of redundancy
- “calling in an army”

Question 10

Immune conservation occurs across what 2 dimensions?

Answer 10

1. Phylogeny: evolution over millions of years
2. Ontogeny: development from embryo -> fetus -> adult

*Both phylogeny and ontogeny play critical roles int eh repertoire of immune antimicrobial mechanisms exhibited across animal species today

Question 11

Is conservation consistent across the spectrum of immune responses?

Answer 11

No!
- Looking at phylogeny and recognizing the different shifts in immune tools the animal is going to have

Question 12

Innate immunity

Answer 12

Immunity which is not intrinsically affected by prior contact with infectious agents. The innate immunity that an animal has the first time they encounter pathogen A will be equivalent to those the 2nd or 3rd time pathogen infiltration occurs
- wide range, localized, ready to go

Question 13

What is necessary if pathogenic organisms breach external barriers?

Answer 13

Innate mechanisms of immunity

Question 14

What were innate mechanisms of immunity historically considered as?

Answer 14

“Non-specific” antimicrobial systems

Question 15

What are 2 representative mechanisms of innate immunity?

Answer 15

1. Phagocytosis
2. Complement cascades = group of ~20 proteins found in serum that bind to the outside of pathogens allowing for improved killing

Question 16

What is necessary if pathogenic organisms breach innate defenses and spread through host?

Answer 16

Acquired (adaptive) mechanisms of immunity
- adaptable to new situations
- systemic
- forms the basis of immune memory

Question 17

What does ‘exquisite specificity’ refer to in terms of adaptive immunity?

Answer 17

Exquisite specificity = can respond to one thing and not something related

Question 18

What are the pros and cons of conservation of immune response?

Answer 18

Pros
- Time proven strategy for elimination of infiltrating pathogens (aka building on a tool that is already fxnl and shows it is possible)

Cons
- Many pathogens can jump from species to species; if the organism overcame the response in one organism, it will likely do the same in another

Question 19

What is comparative immunology? Why is it important?

Answer 19

Comparative immunology: the study of immune responses across all animals
- Take home message: must look beyond a single species
- Must be able to CRITICALLY ASSESS the potential for conservation and divergence btw species as you consider animal health issues

Question 20

What do differences across species reflect? What about similarities?

Answer 20

Difference across species reflect choices made during evolution.

Similarities may point to indispensable or effective mechanisms of immunity.

Question 21

Microorganisms are not just the “bad guys”, what’s an example?

Answer 21

Gut microflora
- aid in breakdown of otherwise undigestible food components
- provide vitamins
- contribute to development of intestinal epithelium, vasculature, and lymphoid tissue
- take up space and compete with incoming pathogens
- promote development of host immune repertoire

Question 22

Each host cell must properly control several functions, what are they?

Answer 22

1. Proliferate
2. Repair DNA
3. Apoptosis
4. Differentiate (mature)
5. Migrate
6. Take in nutrients

Question 23

Immune cells must properly control several functions, how do they decide what to do?

Answer 23

• Signaling pathways help integrate extracellular and intracellular signals
• These pathways converge at the level of gene expression; transcription factors activate genes and this is what determines length and strength of response

Question 24

What dictates the cellular response that follow signaling pathways?

Answer 24

Protein fxn (not gene expression) dictates the cellular response that results

Question 25

Why does animal health often require broader considerations than human health?

Answer 25

• likely multiple hosts in close quarters with multiple pathogens in stressful conditions
• many animals not selected for based on immune parameters