1. Basic concepts of animal immunology Flashcards
What is the goal of immunity?
The goal of immunity is to help return the body to a state of homeostasis
Broadly, how does the immune system help achieve the goal of returning the body to a state of homeostasis?
Defending the host, cleaning up debri/spent cells, and controlling tissue damage
What are 3 examples of different innate and adaptive mechanisms? Are they mutually exclusive?
- Local vs. systemic
- Innate vs. adaptive
- Humoral vs. cell-mediated
*These terms are NOT mutually exclusive; high level of complementarity btw these immune tools
What are strong drivers for evolution of immune defense mechanisms?
Host-pathogen interactions
- continue to shape novel pathogen infection strategies and host mechanisms that can overcome these developing infections
For invading microbes, what has been the challenge in terms of evolution of host-pathogen interactions?
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
For the animal host, what has been the challenge in terms of evolution of host-pathogen interactions?
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
How does the animal host achieve its ultimate goal of avoiding death from infection?
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
Functional redundancy
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
Functional pleiotropy
Capacity of immune tools to exhibit a wide variety of biological fxns on various tissues and cells
- opposite of redundancy
- “calling in an army”
Immune conservation occurs across what 2 dimensions?
- Phylogeny: evolution over millions of years
- 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
Is conservation consistent across the spectrum of immune responses?
No!
- Looking at phylogeny and recognizing the different shifts in immune tools the animal is going to have
Innate immunity
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
What is necessary if pathogenic organisms breach external barriers?
Innate mechanisms of immunity
What were innate mechanisms of immunity historically considered as?
“Non-specific” antimicrobial systems
What are 2 representative mechanisms of innate immunity?
- Phagocytosis
- Complement cascades = group of ~20 proteins found in serum that bind to the outside of pathogens allowing for improved killing
What is necessary if pathogenic organisms breach innate defenses and spread through host?
Acquired (adaptive) mechanisms of immunity
- adaptable to new situations
- systemic
- forms the basis of immune memory
What does ‘exquisite specificity’ refer to in terms of adaptive immunity?
Exquisite specificity = can respond to one thing and not something related
What are the pros and cons of conservation of immune response?
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
What is comparative immunology? Why is it important?
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
What do differences across species reflect? What about similarities?
Difference across species reflect choices made during evolution.
Similarities may point to indispensable or effective mechanisms of immunity.
Microorganisms are not just the “bad guys”, what’s an example?
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
Each host cell must properly control several functions, what are they?
- Proliferate
- Repair DNA
- Apoptosis
- Differentiate (mature)
- Migrate
- Take in nutrients
Immune cells must properly control several functions, how do they decide what to do?
- 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
What dictates the cellular response that follow signaling pathways?
Protein fxn (not gene expression) dictates the cellular response that results
Why does animal health often require broader considerations than human health?
- likely multiple hosts in close quarters with multiple pathogens in stressful conditions
- many animals not selected for based on immune parameters
