Animal: Lecture 7

Question 1

What is innate immunity?

Answer 1

Innate immunity is something that all animals have.
- Involves the recognition of traits shared by broad ranges of pathogens or bacteria using a small set of receptors to recognize it.
- Rapid response: almost immediate

Question 2

What is adaptive immunity?

Answer 2

Adaptive immunity is something only vertebrates (animals with a backbone) have.
- Recognition of traits specific to particular pathogens or bacteria, using a vast array of receptors to find a lock and key to this pathogen (very direct)
- It is a slower response but more directed.

Question 3

What are the types of innate immunity?

Answer 3

• Barrier defenses
• Internal defences

Question 4

Barrier defences?

Answer 4

skin, mucus membranes, and secretions

Question 5

Internal defenses?

Answer 5

phagocytic cells, natural killer cells, antimicrobial proteins, and the inflammatory response

Question 6

What are the types of adaptive immunity?

Answer 6

• Humoral response
• Cell-mediated response

Question 7

Humoral response?

Answer 7

About bodily fluids. Antibodies defend against infection in bodily fluids

Question 8

Cell-mediated response?

Answer 8

Works with cells that are already infected. Cytotoxic cells defend against infection in body cells.

Question 9

What do barrier defenses do?

Answer 9

Barrier defenses prevent most
pathogens from entering the body

Skin/Shells/Cuticle
– Thickened outer surface inhibits entry by pathogens

Mucous membranes
– Mucus secreted by internalized external surfaces traps microbes and other particles
- Internalized surfaces include in the mouth and nose (mucus refers to snot)

Secretions – saliva, tears
– Washing action prevents microbial colonization
– Hostile chemical environment: Lysozyme, acidic pH
- Growth of pathogens is prevented and we flush them out to avoid them colonizing.

Question 10

Internal defense: Phagocytic cells?

Answer 10

Recognize molecules characteristic of a set of pathogens.
- recognizes that an object is foreign and does not belong.

That recognized molecule is absent from vertebrates and is an essential component of certain groups of pathogens.
- That is, without the essential component, the pathogen would not survive.

Why is it important for the component to be essential to the pathogen?
- The pathogen might end up going hidden if the vital component goes unnoticed - it could still be able to evolve.

Question 11

What do phagocytic cells do and where are they located?

Answer 11

They destroy pathogens by phagocytosis (eating other cells).

They are located in:
- Blood
- Skin
- Mucous membranes
- Lymph

Examples: neutrophils and macrophages

Question 12

Process of phagocytosis?

Answer 12

1. Pathogen is located by the cell
2. The pathogen is engulfed into a vacuole (separated in a bubble)
3. A lysosome containing digestive enzymes fuss with the vacuole containing the pathogen
4. The pathogen is digested
5. The waste is released

Question 13

Lymphatic system?

Answer 13

The role of our lymphatic system is to maintain our immune system.C

Question 14

Capillaries and lymphatic vessels?

Answer 14

Very connected with the circulatory (capillary) system (allows a farther reach).

Question 15

Lymph nodes?

Answer 15

Lymph nodes become swollen/inflammed when fighting an infection.

They house many defensive cells for our immunity: like macrophages and other defensive cells.
- When an infection comes, they are released to help.

Question 16

Lymphatic system - issue?

Answer 16

Lymphatic system is very closely associated with the circulatory system and the immune system.
- When we have an issue, defensive cells have to travel from nodes, via the lymphatic vessels.

Question 17

Lipid digestion?

Answer 17

Lipids are diverted to lymph as molecules are too large and need to be broken down by lymph first.

Question 18

Role of lymph system?

Answer 18

It will bring back leaked fluid into the circulatory system when blood leaks onto other tissues.
- It returns the clean blood to the circulatory system

1. Leaked fluid
2. Gathered by lymph node
3. Checks for pathogens
4. Returns to the circulatory system.

Question 19

Internal defence - natural killer cells?

Answer 19

Natural killer cells are a kinds of lymphocyte (white blood cell in lymphatic system)

Recognize surface proteins of virus-infected or cancerous cells. The result of recognition is the release of chemicals that cause apoptosis (cell death) in infected or cancerous cells

Question 20

Internal defence - antimicrobial proteins?

Answer 20

They attack pathogens or impede their reproduction. Therefore, they prevent bacteria/viruses from ever dividing.

Question 21

Interferons?

Answer 21

Proteins secreted by virus-infected cells.
- They trigger surrounding cells to produce chemicals that inhibit viral reproduction
- Therefore, they prevent further reproduction and infection spread

Question 22

Complement Proteins?

Answer 22

Are plasma proteins activated by substances on the surface
of many microbes
– Lead to lysis of invading cells
– Also involved in inflammation and in adaptive immunity
- When they are activated they come together and form a structure which embeds itself into the membrane forming a tube, allowing fluid and salts through. Therefore, the cell bursts open (lysis).

Question 23

Internal defence - inflammatory response?

Answer 23

Signalling molecules are released by injured or (flu) infected tissue causing local inflammation (sore throat or redness).

Question 24

Histamine?

Answer 24

– Triggers vasodilation and increased blood vessel permeability (they have a larger area) in affected area (brings blood to the surface of the body)
– More white blood cells and proteins can enter interstitial fluid as a result. (bringing more blood means there is more redness).

Question 25

Cytokines?

Answer 25

They are secreted by white blood cells, and further increase blood flow to the affected. This, as a result, brings in more white blood cells.

Question 26

Process of the inflammatory response?

Answer 26

- Signalling molecules cause capillaries to dilate (e.g., histamines) and increase blood flow (e.g., cytokines) - The phagocytic cells (e.g., neutrophils), activated complement proteins, and other antimicrobial proteins arriving from the blood work together to fight the infection

Question 27

3 steps of inflammatory response?

Answer 27

1. At the injury site, mast cells release histamines, and macrophages secrete cytokines. These signalling molecules cause nearby capillaries to dilate. 2. Capillaries widen and become more permeable, allowing fluid containing antimicrobial peptides to enter the tissue. Signals released by immune cells attract neutrophils. 3. Neutrophils digest pathogens and cell debris at the site and the tissue heals.

Question 28

Systemic inflammatory response?

Answer 28

A serious (flu) infection can cause a systemic inflammatory response (e.g., fever) – Release more white blood cells from the bone marrow (where all wbc are made) – Reset body’s thermostat to cause fever - Fever induces phagocytosis, some enzymes become active with heat and others make more white blood cells.

Question 29

Histamine increases local blood flow. This leads to the arrival of blood cells that release cytokines that promote local blood flow. A. This is an example of negative feedback B. This is an example of positive feedback

Answer 29

B. This is an example of positive feedback.

Question 30

Adaptive immunity evolves?

Answer 30

Adaptive immunity involves pathogen-specific recognition

Question 31

How is specificity achieved?

Answer 31

Specificity is achieved through interactions between antigens and antigen receptors?

Question 32

Antigens?

Answer 32

Antigens are large molecules found on the surface of specific pathogens or secreted by those pathogens

Question 33

Antigen receptors?

Answer 33

Antigen receptors are proteins produced by B cells or T cells, and bind to antigens like a "lock and key". B and T call are a type of lymphatic cell and they are site specific.

Question 34

Antigens contain...?

Answer 34

Antigens contain multiple epitopes.

Question 35

Epitopes?

Answer 35

An epitope is a small, accessible portion of an antigen that binds to an antigen receptor - epitopes allow antigen receptor of B cell to bind to it.

Question 36

An immune system that is able to recognize multiple epitopes of a single antigen molecule is advantageous because... A. Some of the epitopes do not trigger an immune response B. It is less likely that multiple epitopes will mutate than it is that one epitope will mutate C. Some of the epitopes are hidden inside the pathogen

Answer 36

B. It is less likely that multiple epitopes will mutate than it is that one epitope will mutate. - One type of B or T cells that can recognize something in a group. of them.

Question 37

B and T cells are...?

Answer 37

B and T cells are lymphocytes.

Question 38

Lymphocytes?

Answer 38

Lymphocytes are white blood cells; produced in the bone marrow – B cells mature in the bone marrow – T cells migrate to the thymus for maturation

Question 39

Each B or T cell produces?

Answer 39

Each B or T cell produces a single type of antigen receptor. - Variety = better chance of fighting - Variety of antigen receptors for a variety of potential epitopes on virus/bacteria.

Question 40

Each antigen receptor?

Answer 40

Each antigen receptor binds to a single epitope of a single antigen.

Question 41

Variable regions?

Answer 41

Variable regions of antigen receptors produce the specificity of the antigen-binding site. - Creates specific binding site for epitope - Vary from one cell to another - Variable regions allow multiple epitopes to be recognized

Question 42

Humoral response?

Answer 42

Humoral Response: B cell antigen receptors bind to intact antigens in the blood or lymph - These antigens may be on the surface of pathogens or may be free antigens secreted by pathogens. - B cells: bind things that are not supposed to be in blood - lymph fluid.

Question 43

Cell-mediated response?

Answer 43

Cell-Mediated Response: T cell antigen receptors can only bind to antigen fragments presented on the surface of host cells. - MHC molecule is attached to the antigen fragment to display it like a tag! - The T cell antigen receptor is able to connect to the antigen fragment.

Question 44

B and T cells do what when they encounter epitope?

Answer 44

B cells and T cells proliferate when they encounter their specific epitope - Hopefully they will be able to find and fight more of the viruses that are floating around or invade infected cells. - Proliferate = they divide when they connect the epitope.

Question 45

What kind of cells are there?

Answer 45

Effector cells and memory cells.

Question 46

Effector cells?

Answer 46

Effector cells * Short-lived cells that take effect immediately against the pathogen or antigen

Question 47

Memory cells?

Answer 47

Memory cells * Long-lived cells that give rise to effector cells if the same epitope is encountered again * When we do blood work, we can tell if an infection has been present before because of the memory cells.

Question 48

Effector forms of B cells?

Answer 48

Effector forms of B cells are plasma cells, which secrete antibodies - Antibodies are soluble forms of the antigen receptor; specific for the same epitope as the original B cell - Antibodies are released from the plasma cells, then they float around the blood system.

Question 49

Antibodies?

Answer 49

Antibodies mark pathogens for inactivation or destruction: - Neutralization prevents pathogen entry into cells - Toxins can also be neutralized by antibodies.

Question 50

Antibody binding?

Answer 50

Antibody binding to sites on the pathogen increases the ability of phagocytic cells to recognize the pathogens. - This leads to increased phagocytosis of pathogens! - The macrophage or neutrophil has an increased ability to recognize things as foreign objects.

Question 51

Antibodies activate?

Answer 51

Antibodies activate the complement system, leading to the formation of pores. - Formation of membrane attack complex allows the flow of water and ions, leading to pathogens lysing and bursting.

Question 52

Effector forms of T cells are..?

Answer 52

Effector forms of T cells are helper T cells and cytotoxic T cells. - Cytokines from helper T cells help activate B cells and cytotoxic T cells - Cytotoxic T cells secrete proteins that lead to cell death in infected cells. - Helper T cells help activate B cells and cytotoxic T cells.

Question 53

Cytotoxic T cells?

Answer 53

Cytotoxic T cells bind to infected cells and secrete perforin & granzymes. This ensures that apoptosis is initiated, therefore no more virus is being spread.

Question 54

Perforin?

Answer 54

Perforin causes pores to form in the cell membrane of infected cells (burst and die)

Question 55

Granzymes?

Answer 55

initiate apoptosis (cell death)

Question 56

Memory cell responsibility?

Answer 56

Memory cells are responsible for long-term protection provided by a prior infection or vaccination. -Memory cells, produced during the original B cell or T cell proliferation, give rise to effector cells if the same epitope is encountered again – Secondary immune response ➔ rapid

Question 57

Primary vs. Secondary response?

Answer 57

- Primary immune response to antigen A produces antibodies to A. - Secondary immune response to antigen A produces antibodies to A; primary immune response to antigen B produces antibodies to B.