Lecture 2 - Innate Immunity I

Question 1

Innate Immunity

Answer 1

The first and second line of non-specific defenses that exist in all organisms in various ways

Question 2

1st line of defense

Answer 2

First part of innate immunity.

A non-specific defense that involves skin, mucus, membranes, and chemicals

Question 3

2nd line of defense

Answer 3

Second part of innate immunity.

A non-specific defense that involves phagocytosis, complement, interferon, inflammation, and fever

Question 4

Fundamentals of Innate Immunity

Answer 4

1. Protective mechanism that exists before infection
2. Rapid responses encoded within the germline (DNA in egg and sperm cells)
3. Responses are typically identical upon repeat infection

Question 5

Inflammation

Answer 5

Part of the 1st line of defense

Involves vasodilation, increase in capillary permeability, and influx of immune cells to affected tissues.

Question 6

Four signs of inflammation

Answer 6

REDNESS: Vessels dilate (vasodilation) and blood volume increases

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

Question 7

Evidence of Inflammatory Response: Elie Metchnikoff (1800s)

Answer 7

Insult to star-fish larvae with thorn, rapid localization of cells to site of insult, breakdown of thorn by cells

(First observation of phagocytosis)

Question 8

Inflammatory Response

Answer 8

1. Margination: inflammatory chemicals and mast cells leave the bloodstream and move towards infection
2. Diapedesis: the Neutrophils leave the bloodstream and head towards the infection
3. Chemotaxis: the Neutrophils locate the bacteria through chemical signals
4. Phagocytosis: the Neutrophils engulf the bacteria and digest them

Question 9

Phagocytosis

Answer 9

“Cellular eating”. Process by which a cell engulfs a substance by surrounding it with its membrane

Highly Conserved throughout Evolution

Steps:
1. Phagocytes detects and engages microbe
2. Microbe engagement initiates cytoskeletal rearrangements that drive phagocytosis
3. The microbe is internalized in a specialized phagosome.
4. The phagosome fuses with the lysosome to form a phagolysosome
5. Lysosomal enzymes destroy ingested microbes.
6. Reactive oxygen and nitrogen intermediates destroy microbial proteins, genomes and walls

Question 10

Phagocytes

Answer 10

“Cell that eats”

Cells that ingest and destroy microbes by a process known as phagocytosis. They also activate neighbouring cells through the release of cytokines and chemokines

Two processes:
1) Chemotaxis — chasing down of microbes
2) Phagocytosis — eating of microbes

Eg. Macrophages, Monocytes, and Neutrophils

Question 11

Macrophage Development

Answer 11

1. Bone Marrow Stem Cell: undifferentiated stem cells in the bone marrow
2. Blood Monocyte: differentiation into short-lived monocytes that circulate in the blood
3. Tissue Macrophage: Inflammation recruits monocytes to sites of infection where they differentiate into resident macrophages
4. Resident macrophages are long-lived “professional” phagocytes that ingest large amounts of extracellular material

Question 12

Cytokines

Answer 12

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

Question 13

Chemokines

Answer 13

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