Lecture 2: Innate Immunity I Flashcards
_________ exists across all types of organisms in a variety of ways
Immunity
Nonspecific defenses (Innate Immunity)
1st line: skin, mucous membranes, chemicals
2nd line: Phagocytosis, complement, interferon, inflammation, fever
Specific defenses (Adaptive Immunity)
3rd line: Lymphocytes, antibodies
Fundamentals of Innate Immunity (3)
- Protective mechanism that exists before infection
- Rapid responses encoded within the germline (DNA in egg and sperm cells)
- Responses are typically identical upon repeat infection. No improvement on innate immune response
Innate immune cells
Ready to act immediately
What is a limitation of innate immunity?
No memory
How long does it usually take for an innate immune response?
6-12 hours
Example of cells involved in innate immunity?
Phagocytes, Dendritic cells, Complement cells, Natural killer cells
Inflammation
Mobilizing bodily defenses at sites of infection.
Happens when there’s pathogen present
What happens during an inflammation?
- vasodilation
- increase in capillary permeability
- influx of immune cells to affected tissues
4 Signs of Inflammation
- Redness- vessels dilate (vasodilation) and blood volume increases
- appear more red because there’s more RBC; more WBC too - Heat- increased blood volume brings warmth to affected tissue
- Edema- swelling due to accumulation of fluid from blood in affected tissue
- Pain- some inflammatory mediators trigger the pain response
Evidence of Inflammation: Elie Metchnikoff (1800s)
- insult to starfish larvae with thorn. Starfish have innate immunity
- rapid localization of cells to site of insult
- breakdown of thorn by cells
- first observation of process known as phagocytosis
Processes involved in inflammatory response
- Margination- migration of WBCs toward the endothelium during blood flow
- Diapedesis- leukocytes squeezes in amoeboid fashion across the endothelial cells
- Chemotaxis- directed migration of a cell in response to a chemical stimulus
- Phagocytosis- cell eating
Phagocytosis is highly conserved throughout _________
evolution
Phagocytes
(“cell that eats”) ingest and destroy microbes by a process known as phagocytosis
Examples of Phagocytes
Macrophages, Monocytes, neutrophils
Chemotaxis
chasing down of microbes
Phagocytosis
eating of microbes
TRUE or FALSE
There is a variety of microbial products
TRUE
In an immune response, there are shared ________ _________
signaling pathways
Steps in Phagocytosis
- Phagocytes detects and engages microbe
- Microbe engagement initiates cytoskeletal rearrangements that drive phagocytosis
- The microbe is internalized in a specialized phagosome
- The phagosome fuses with the lysosome to form a phagolysosome
- Lysosomal enzymes destroy ingested microbes
- Reactive oxygen and nitrogen intermediates destroy microbial proteins, genomes and walls
Macrophage Development
- Like all blood cells, macrophages arise from undifferentiated stem cells in the bone marrow.
- Some stem cells differentiate into short-lived monocytes that circulate in the blood.
- Inflammation recruits monocytes to sites of infection where they differentiate into resident macrophages
- Resident macrophages are long-lived “professional” phagocytes that ingest large amounts of extracellular material.
Aside from eliminating microbes, what else do phagocytes do?
They activate neighboring cells through the release of cytokines and chemokines
Cytokines
Secreted proteins that drive immune and inflammatory reactions.
In innate immunity, cytokines are produced by macrophages and natural killer cells
One effect of cytokines
Induce proteins in the endothelium that make the endothelium more adherent for passing leukocytes
Chemokines
A large family of structurally related, low molecular weight cytokines that stimulate leukocyte movement and regulate the migration of leukocytes from the blood to tissues
What is the first step in innate immunity?
The detection of microbes by innate immune resident cells in tissue (e.g. macrophages)
Microbe engagement triggers inflammation at the ________
site of infection
resident and recruited macrophages engulf and destroy invading microbes, via ___________, and activate additional responses _____________ production
phagocytosis, cytokine/chemokine production
