(Section B: Immunology) Lecture 10: Innate Immunity I Flashcards
True or False:
Innate Immunity and Adaptive Immunity are separate systems
False, they are intertwined different types of responses of the immune system
Which type of immune response came first?
Innate immunity came first
For Adaptive and Innate Immunity, compare:
Source
Innate
* Germ line encoded genes
Adaptive
* Recombination of genes
* Very rapid changes
For Adaptive and Innate Immunity, compare:
Inheritance
Innate
* Inherited
Adaptive
* Non-inherited
For Adaptive and Innate Immunity, compare:
Specificity
Innate
* Recognizes evolutionarily conserved molecular patterns
Adaptive
* Recognizes dynamically changing molecular patterns
For Adaptive and Innate Immunity, compare:
Memory
Innate
* Epigentic imprinting of past pathogen encounters
Adaptive
* Survival of clone cells expressing specific receptors to past antigens
For Adaptive and Innate Immunity, compare:
Structure
Innate
* Physical barriers
* Chemical defenses
* Cellular responses
Adaptive
* Cellular responses
* Antibody production
For Adaptive and Innate Immunity, compare:
Dynamics
Innate:
* Present in individuals at all times
Adaptive:
* Formed as antigens are encountered
What are the 6 ways that innate and adaptive immunity differ?
- Source
- Inheritance
- Specificity
- Memory
- Structure
- Dynamics
What aspects of the immune system are there?
- Innate
- Adaptive
- Cellular
- Humoral
Cellular Immunity
Cell-based immunity
* Cells recognize another cell to destroy
* Mediated by living cells
Humoral Immunity
Refers to liquids (humors)
* Molecules that are soluble in liquids of the body (blood, plasma, saliva, tears etc.)
* Involves antibodies
Which 2 scientists are considered the founders of immunology?
Ehrlich and Metchnikoff
What is Metchnikoff known for?
- Embryologist
- Cellular and Innate Immunity
- Phagocytosis
- Macrophages
What is Ehrlich known for?
- Chemist
- Humoral and Adaptive Immunity
- Antibodies
- Side chain theory
Explain blood composition
- 55% plasma (blood hormones, clotting factors, antibodies, proteins, enzymes etc.)
The rest is comprised of cells
* ~1% buffer coat (leukocytes, WBCs, platelets)
* 45% erythrocytes (RBCs)
Hematopoesis
Blood Cell Formation
How does hematopoesis work?
- Hematopoetic stem cells (self renewing)
- Differentiates into myeloid progenitor and lymphoid progenitor
What cells are of myeloid origin?
- Neutrophils
- Monocytes/Macrophages
- Dendritic cells
What cells are of lymphoid origin?
- B cells
- T cells
- Innate lymphoid cells
Cells of the Immune System:
Lymphocytes
Split into:
* T cells
* B cells
* Innate lymphoid cells (ILCs)
What aspect of the immune system do T cells belong to?
Cellular adaptive immunity
What aspect of the immune system do B cells belong to?
Humoral adaptive immunity
Give an example of an innate lymphoid cell
NK (Natural Killer) Cells
What are characteristics of lymphocytes?
- Small cytoplasm
- Large nucleus
- Small cell size
ILCs have small granules
Cells of the Immune System:
Mast Cells
“Well fed”
* Stuffed with granules, seen in staining
What do granules in mast cells produce?
Produce and release histamine
Where are mast cells found?
Epithelial barrier tissues
What do histamines do?
Signals to open up blood flow
Where are examples of locations that mast cells would be found?
- Lung
- Digestive tissues
- Skin
Cells of the Immune System:
Eosinophils and Basophils
Eosinophils
* “Dye loving”
* Granules stain pink
Basophils
* “Base loving” - loves basic dyes
* Granules stain blue
What do basophils contain?
Glycogen
What roles do eosinophils and basophils play in the immune system?
Play roles in allergies and parasitic reactions
Cells of the Immune System:
Neutrophils
“Neutral pH”
What is the structure of neutrophils?
Has segmented nucleus
* Helps them squeeze through tight spaces to reach injury
Contains granules
What is the lifespan of neutrophils?
Short lifespan: A few days
Macrophages vs. Microphages
Macrophages - “Big eaters”
Microphages - “Small eaters”
What percentage of cells do neutrophils make up?
A majority of the WBCs
* 50-70% of blood circulating leukocytes
What do dead neutrophils appear as?
Dead neutrophils appear as pus (yellowish substance at sites of infections)
What is the mechanism of neutrophils?
- Signalled to exit bloodstream by injury
- Large numbers swarm injury sites
What process can neutrophils undergo?
- Phagocytosis
- Netosis
Describe the process of netosis
- Stimuli sends activation signal to neutrophil
- Neutrophil “throws out” or expels chromatin nets
- Nets ensnare extracellular pathogens
What are the chromatin nets like in netosis?
Decorated with antimicrobial proteins
* More than 20 different proteins including antimicrobial peptides, MPO, elastase
Cells of the Immune System:
Dendritic Cells
“Branching cells”
What are the branches of a dendritic cell known as?
Processes or Pseudopodia
What is the structure of dendritic cells?
Contains lysosomes and phagosomes
* Lysosomes are acidic
Where are dendritic cells present?
In the tissues
What are the dendritic cells commonly known as?
Professional phagocytes
* Just eats cells all the time
Cells of the Immune System:
Monocytes
- Present in the blood
- Can differentiate into macrophages
Cells of the Immune System:
Macrophages
“Big eater”
Where are macrophages present?
In various tissues of the body
What roles do macrophages play?
- Highly phagocytic
- Removes pathogens and body cells
- Involved in tissue remodeling (ex. removing webbing between fingers)
Are monocytes phagocytic?
Yes
Do macrophages have different functions?
Yes, they have specialized functions depending on which tissue they live in
What is the lifespan of a macrophage?
Long lifespan
* Months to years
What are the steps to phagocytosis? (5)
- Bacterium binds to PRRs on membrane evaginations called pseudopodia (processes, dendrites)
- Bacterium is ingested forming phagosome
- Phagosome fuses with lysosome
- Bacterium is killed and then digested by low pH-activated lysosomal enzymes
- Digestion products are released from cell
Phagocytosis:
What are phagosomes essentially?
Vacuoles that engulf bacterium
Phagocytosis:
Describe the environment of a lysosome
- Low pH (4.5)
- Enzymes activated to digest material
Phagocytosis:
Where does the digestion products go?
- Disposed
- Can be given to immune system to start immune response
- Can be recycled
List:
Phagolysosome antimicrobial properties
- Low pH
- NADPH oxidase: Reactive oxygen species that kills
- Myeloperoxidase (MPO): Transforms hydrogen peroxide into hypochlorous acid (bleach)
- Lactoferrin: Captures Fe2+ that is essential for bacterial growth
- Defensins: Punches pores into the bacteria
- Lysozyme: Degrades peptidoglycan
What happens to bacteria that survive phagocytosis?
Can live/replicate inside a phagocyte
* In the phagosome, phagolysosome, or escape to neighboring cells
What are methods that bacteria can survive phagocytosis with?
- Inhibition of phagosome-lysosome fusion
- Survival mechanisms to the inside of the phagolysosome
- Degradation of phagolysosome (to escape into cytoplasm and reproduce)
What bacteria are professional intracellular pathogens?
- Salmonella
- Mycobacterium
- Listeria monocytogenes
- Staphyloccocus aureus