The Immune System - Antigen Recognition (w11)

Question 1

What are the two systems of immunity ?

Answer 1

innate immunity / nonspecific resistance
adaptive immunity / specific immunity

Question 2

What is innate immunity ?

Answer 2

A response to pathogens that is the same each time the body is exposed

Question 3

What is adaptive immunity ?

Answer 3

A response to pathogens which improves each time the pathogen is encountered.
Characteristics: Specificity and memory

Question 4

How is adaptive immunity specific ?

Answer 4

Adaptive immunity recognises a particular substance for example a specific virus or bacteria

Question 5

How does adaptive immunity use the characteristic of ‘memory’ ?

Answer 5

The adaptive immune system “remembers” previous encounters with a particular substance. This means a that future responses are faster, stronger, and longer-lasting

Question 6

When is a person classed as immune ?

Answer 6

If the pathogen is destroyed before any symptoms develop.

Question 7

What are the physical barriers of the immune system ?

Answer 7

• skin
• mouth/ oral cavity
• stomach/GI tract
• mucosal epithelia
• tears, saliva, urine

Question 8

What is the point of chemical mediators ?

Answer 8

They are released by cells and promote the immune response

Question 9

How to complement proteins contribute to the adaptive and innate systems ?

Answer 9

• Bind to the cell membrane of the pathogen labelling it for phagocytosis (opsonization)
• Act as chemotactic agents to attract phagocytic cells to the site of inflammation
• Form damaging pores in the plasma membrane of the pathogen -Cells swell and lyse (rupture)

Question 10

What are cytokines ?

Answer 10

Small signalling molecules that are released from cells to trigger immune response
Egs Interleukins + chemokines + interferons

Question 11

What are three examples of cytokines ?

Answer 11

1) interleukins
2) chemokines
3) interferons

Question 12

What is the function of interferons (INFs) ?

Answer 12

They are secretes by cells infected with a virus and travel to adjacent cells, inducing them to make antiviral proteins, these prevent the production of new viral nuclei acids and proteins and overall inhibit viral reproduction in these surrounding cells.
- some INFs also activate other immune cells such as macrophages

Question 13

List three other chemical mediators ?

Answer 13

• histamines
• prostaglandis
• leukotrienes

Question 14

How can some chemical mediators such as histamines and leukotrienes be useful in immune response ?

Answer 14

They can cause :
- vasodilation, which increases vascular permeability stimulating phagocytosis.
- this promotes inflammation

Question 15

Where are white blood cells produced ?

Answer 15

In the red bone marrow/ lymphatic tissue

Question 16

What attracts white blood cells ?

Answer 16

The chemicals released from either pathogens or damaged tissues

Question 17

What are the two types of phagocytic cells ?

Answer 17

• neutrophils
• macrophages

Question 18

What is the function of neutrophils in the immune response ?

Answer 18

They are usually the fist cells to respond and they release signals that increase the inflammatory response, this recruits and activates other immune cells

Question 19

What is the function of macrophages in the immune response ?

Answer 19

Macrophages are monocytes that leave the blood and are usually secondary to neutrophils. They are much larger and are used during the later stages of an infection. They clean up these dead neutrophils and other cellular derbies and microorganisms by engulfing them. These damaged tissues are then repaired.

Question 20

What are the 3 examples of inflammatory cells ?

Answer 20

• basophils (mobile cells)
• mast cells (non Mobile cells in connective tissue)
• eosinophils (allergic response)

Question 21

What happens when inflammatory cells are activated ?

Answer 21

They release histamines and leukotrienes
- this is called the inflammatory response

Question 22

What is the function of natural killer cells in the immune response ?

Answer 22

NK cells recognize the different classes of cells, (eg tumour cells / virus-infected cells) they then kill their target cells,
releasing chemicals that damage cell membranes this causes the cells to lyse.

Question 23

What happens during the inflammatory response ?

Answer 23

• The injured tissue (e.g bacterial infection causing damage) causes mast cells and basophils to degranulate.
• This stimulates the release or activation of chemical mediators. (Such ads histamines, leukotrienes, complement, prostaglandins)
• These chemical mediators cause vasodilation (particularly the histamines and prostaglandins) this mean local capillaries dilate, increasing blood flow.
• This increase blood flow brings WBC and phagocytes to the infected area causing heat and redness.

Question 24

What chemical mediators causes increased vascular permeability, and how do they cause this ?

Answer 24

Histamines
- leakage of fluid into tissue causes swelling /oedema
- This Allows complement to enter tissue which enhances inflammatory response / attracts more phagocytes.
- Then clotting factors enter (fibringogen- fibrin) –
Wall off/ first step in wound repair

Question 25

When does the inflammatory response stop ?

Answer 25

When pathogens are destroyed.

Question 26

How do you know if the inflammatory response is local ?

Answer 26

• if there is redness, heat, swelling or pain

Question 27

Hi do you know if the inflammatory response is systemic ?

Answer 27

• if the reaction is more widespread
• there will be more neutrophils
• if a fever is caused
• in severe cases: sepsis - this causes decreased blood volume and can cause shock or death.

Question 28

How can fever and inflammation be beneficial ?

Answer 28

• increases temperature which promotes phagocytosis
• decreases microbial growth

Question 29

What does inflammation facilitate the transport of ?

Answer 29

Antigens to the lymph nodes ( this is important for adaptive immune response )

Question 30

What is adaptive immunity ?

Answer 30

• it is anybody mediated and is known as humoral immunity .
• the proteins are generated by plasma cells and are differentiated B cells.

Question 31

Where to lymphocytes originate form ?

Answer 31

• the stem cells in the red bone marrow.
  —> B cells mature in red bone marrow
  —> T cells mature in thymus

Question 32

Describe the adaptive immune response ….

Answer 32

• Antigen recognition by lymphocytes activates this causes lymphocyte receptors and antigens to combine (B cell and T cell receptors)
• Proliferation of lymphocytes then recognises that antigen
• Antigens may be part of larger molecules
  (Eg after phagocytosis and b/d by macrophages)
• these are bound to major histocompatibility complex molecules (MHC) on the cell surface

Question 33

What does the specific reps ones consist of ?

Answer 33

• antibody mediated response
• cell mediated response

Question 34

What is part of the non specific response ?

Answer 34

• physical barriers
• chemical mediators
• leukocytes (wbc)
• inflammatory response

Question 35

What happens after a pathogen is phagocytosed ?

Answer 35

After a pathogen is phagocytosed the antigen is presented on the surface of a cell (eg macrophage) by the MHC molecule