Topic 4: The Immune System

Question 1

What does the human immune system do? What
role does it play?

Answer 1

Theimmune systemis the body system that prevents and fights disease. It is made up of many organs, tissues and cells working together. -fights both infectious diseases, like measles, and non-infectious diseases, like cancer.

Question 2

What is the difference between specific and non-specific defense of the body?

Answer 2

specific: the response will be tailored to the specific invading agent

non-specific: the response will be the SAME regardless of the TYPE of pathogen

Question 3

How does the body recognise self from non-self?

Answer 3

Body cells have antigens recognised by the immune system, and no immune response will be mounted against these cells. Foreign invaders have antigens that the immune system does not recognise and an immune reaction will be initiated.

Question 4

What is meant by non-adaptive defense?

Answer 4

the response will not vary in strength and type
to suit the pathogen.

Question 5

What is the first line of defense

Answer 5

Takes place on the body surfaces to try and stop the entry of microorganisms/pathogens

Question 6

Physical barrier role (1st line)

Answer 6

barriersstop pathogens from entering the body by blocking or trapping them.

Question 7

Explain how skin barrier works

Answer 7

The skin is a tough, waterproof barrier that consists or keratinised cells which make the skin tight and tough.
- when skin is cut: rapid blood clotting due to platelet action which seals the wound
- secretes sweat (high salt) and antiseptic bodies which inhibit microbial growth

Question 8

Other examples of first line defense

Answer 8

• ear wax
• mucous membranes

Question 9

What is chemical barriers

Answer 9

barrierskill pathogens before they can enter the body.

Question 10

Example of chemical barrier

Answer 10

Tears/Saliva/Sweat: contain LYSOZYME which are enyzmes that cause breakdown of bacterial cell wall.
- help pathogens flush pathogens out of body
- destroy or inhibit growth of microorganisms

Question 11

What is microbiological barriers

Answer 11

the presence of natural flora found on the skin, gut, and vagina that inhibits the growth of other pathogenic bacteria

Question 12

Is the second line of defense specific or non-specific? Adaptive or non-adaptive?

Answer 12

non-specific, non-adaptive, no memory

Question 12

Example of microbiological barrier

Answer 12

Natural Flora - they are better suited for the environment and dont allow other pathogens to grow
eg; Yakult, yogurt

Question 13

role of macrophages

Answer 13

Carries out phagocytosis of any foreign pathogens. It engulfs, encloses them in a vacuole and digests them with the enzymes from their lysosomes.
- puts a part of the pathogen on the surface and presents it to T-cells to activate them

Question 14

Role of neutrophil

Answer 14

General white blood cells that carry out
phagocytosis. They are the first to the site of
infection in large numbers.
- found commonly in bloodstream and tissues

Question 15

Role of Basophil

Answer 15

A white blood cell that secretes histamine which causes inflammation that brings more blood into the area of the infection. (blood vessels dilate, more blood flow, more WBC)

Question 16

Role of Mast Cell

Answer 16

• fixed cells found in the blood vessels that contain large granules of histamine which they secrete when allergen in encountered

Question 17

Role of Natural Killer Cells

Answer 17

A white blood cell that attacks and destroys any
body cell infected with viruses or cancer. It
releases toxins to destroy cause those cells membrane to burst

Question 18

What happens to lymph node when infection?

Answer 18

it swells and hardens as the lymph cells rapidly reproduce to increase in numbers
- if a virus/bacteria comes in lymph, the WBC destroy it before it moves on, causing glands to swell

Question 19

Steps of phagocytosis

Answer 19

1. Bacterium comes in contact with neutrophil
2. The cell membrane of neutrophil/macrophage engulf the bacterium
3. Neutrophil/Macrophage encloses bacteria into a vacuole
4. Lysosome fuses with the vacuole and releases digestives enzymes to destroy the bacterium

Question 20

What are second line WBC called?

Answer 20

Leucocytes

Question 21

3 defensive chemical molecules

Answer 21

1. Histamine - the process of inflammation
2. Interleukin - the process of fever
3. Interferon - stops viruses replicating

Question 22

Role of Histamine and Inflammation

Answer 22

• basophils/mast cells dump histamine which causes more blood flow into the area.
• this results in vasodilation (widening of capillaries) and increased permeability (leaking capillaries)
• symptoms: redness, pain, swelling

Question 23

Role of interleukin and fever

Answer 23

when macrophages attack invaders they secrete interleukins which cause temperature to rise to slow down pathogens, making it easier for the immune system to react
- causes drowsiness making you reduce activity, and allow for more energy of immune system to fight back
- signalling molecule

Question 24

Interferon and Virus attacks

Answer 24

• a chemical secretes by some virally infected cells, signalling cells that are not yet infected to change their surfaces to make it difficult for virus to infect them
• reduce/slow down the growth of viral pathogen
• can alert apoptosis

Question 25

How is 3rd line different to 2nd and 1st line

Answer 25

it is specific: the response will be tailored to the specific invading agent and it is adaptive: the response varies in strength and type to suit the pathogen. forms a memory of the pathogen

Question 26

Where are B and T cells made and where do they mature?

Answer 26

Lymphocytes = T-cells and B-cells
Created in the bone marrow
T cells mature in the: Thymus Gland
B cells mature in the: Bone Marrow
they both circulate in the blood looking for foreign antigens

Question 27

What is Humoral Response

Answer 27

• B-cell Response
• when b-cells produce antibodies that are secreted into the blood and lymph

Question 28

What is cell-mediated response?

Answer 28

T cells attack the cells that have antigens they recognise

Question 29

Role of Helper T cells

Answer 29

They activate B Cells to become plasma cells make antibodies, and release lymphokines to further inflammation and phagocytosis

Question 30

Role of Cytotoxic T cells

Answer 30

They combine with foreign antigens displayed on surfaces and release powerful chemicals that can directly kill pathogens

Question 31

Role of memory T cell

Answer 31

remain in the blood after pathogens have been killed
- become activated and divide rapidly at the occurrence of a second infection
- quick and strong as they recognise the pathogen

Question 32

What do plasma cells do?

Answer 32

They secrete antibodies

Question 33

Role of memory B cells

Answer 33

may be converted to plasma cells at a later time

Question 34

What do B-cells divide into

Answer 34

1. Plasma cells
2. Memory B cells

Question 35

Activation steps of a B cell

Answer 35

The b cell recognises foreign antigens and breaks them down, leaving pieces on its surface. The activated B cell divides rapidly and creates identical copies of itself called clones.
- receives signals from Helper T-cells to reinforce activation
Then start differentiating into either plasma cells or memory b-cells . The plasma cells become antibody producing factories and release large quantities of antibodies

Question 36

What are antibodies?

Answer 36

specific groups of proteins also called immunoglobulins that are made by plasma cells

Question 37

How do antibodies inactivate a pathogen?

Answer 37

Agglutination - the clumping of antigens and antibodies. Immobilises them from infecting vody cells
- Promotes phagocytosis (macrophages and neutrophils)

Question 38

Primary response to infection

Answer 38

• no memory cells so the antibodies are made slowly and not in large numbers, takes a while and you get sick

Question 39

Secondary response to infection

Answer 39

presence of memory cells from the first infection, recognises the antigen and respond quickly to make antibodies in large numbers, you don’t get sick.