The Immune System

Question 1

What are the 4 types of pathogen?

Answer 1

• bacteria
• viruses
• protoctists
• fungi

Question 2

What is the function of bacteria?

Answer 2

Produce toxins that damage body cells

Question 3

What is the function of viruses?

Answer 3

Use host cells to replicate before bursting out and destroying cells

Question 4

What is the function of protoctists?

Answer 4

Take over cells and break them open

Question 5

What is the function of fungi?

Answer 5

Digest living cells to destroy them and some produce toxins

Question 6

What are the two types of defence mechanism?

Answer 6

• non-specific
• specific

Question 7

What is a non-specific defence mechanism?

Answer 7

Response is the same for all pathogens and act quickly

Question 8

What is a specific defence mechanism?

Answer 8

Response is specific to each pathogen but are slower to defend the body

Question 9

What is an antigen?

Answer 9

A protein found on the cell-surface membrane

Question 10

What allows the immune system to distinguish between the body’s own cells and foreign cells?

Answer 10

Antigens

Question 11

What 4 molecules/cells do antigens allow the immune system to identify?

Answer 11

• pathogens
• abnormal body cells
• toxins
• cells from other organisms of the same species

Question 12

What type of defence is phagocytosis?

Answer 12

Non-specific defence

Question 13

What type of cell are phagocytes?

Answer 13

White blood cell

Question 14

What are the first 3 stages of phagocytosis?

Answer 14

1. Pathogen releases chemicals that attract a phagocyte
2. Phagocyte recognises the pathogen’s antigens as non-self which causes the phagocyte to bind to the pathogen
3. Phagocyte engulfs the pathogen

Question 15

What are the last 3 stages of phagocytosis?

Answer 15

4. The pathogen is now contained within a vesicle known as a ‘phagosome’
5. The lysosome, containing hydrolytic enzymes called lysozymes, fuses with the phagosome to form a phagolysosome
6. Lysozymes digest and destroy the pathogen and the phagocyte presents the pathogen’s antigens on its surface

Question 16

Which type of white blood cell does the specific immune response depend on?

Answer 16

Lymphocyte

Question 17

Where are lymphocytes produced?

Answer 17

Bone marrow

Question 18

What are the two types of lymphocytes?

Answer 18

• T lymphocytes or T cells
• B lymphocytes or B cells

Question 19

What is the function of T cells?

Answer 19

Involved in the cellular response where they respond to antigens presented on body cells

Question 20

What is the function of B cells?

Answer 20

Involved in the humoral response where they produce antibodies found in body fluids

Question 21

What are the 3 types of T cell?

Answer 21

• Helper T cells
• Cytotoxic T cells
• Memory T cells

Question 22

What is the function of Helper T cells?

Answer 22

Have receptors on their cell surface that bind to complementary antigens on APCs. After binding they can form memory cells, stimulate B cells or phagocytes, and activate cytotoxic T cells

Question 23

What is the function of Cytotoxic T cells?

Answer 23

Kill abnormal and foreign cells by producing a protein known as perforin, which makes holes in the cell-surface membrane, causing it to become freely permeable and causing cell death

Question 24

What is the function of memory T cells?

Answer 24

Provide long-term immunity against specific pathogens and provide a rapid response if the body is re-infected by the same pathogen

Question 25

Why is the cellular response called the cellular response?

Answer 25

T cells will only respond to antigens presented on body cells rather than antigens within the body fluid

Question 26

What is the first stage of the cellular response?

Answer 26

Phagocytes engulf pathogens and display their antigens on the cell-surface, known as APCs

Question 27

What is the second stage of the cellular response?

Answer 27

Helper T cells with complementary receptors bind to these antigens

Question 28

What is the third stage of the cellular response?

Answer 28

On binding, helper T cell is activated to divide by mitosis to form genetically identical clones

Question 29

Give 4 functions of the cloned T cells by cellular response

Answer 29

- develop into memory cells - stimulate phagocytosis - stimulate division of B cells - activate cytotoxic T cells

Question 30

What does the humoral response involve?

Answer 30

The production of specific antibodies to destroy pathogens

Question 31

Which type of cells are used in the humoral response?

Answer 31

- B cells - plasma cells - memory cells -helper T cells

Question 32

Why is the humoral response called the humoral response?

Answer 32

Antibodies are found in body fluids, which are otherwise known as ‘humors’

Question 34

What are the first 3 stages of the humoral response?

Answer 34

1. A B cell with a complementary antibody binds to the antigens on a pathogen 2. B cell engulfs the pathogen and presents its antigens on the cell-surface membrane 3. Clonal selection - activated T helper cells bind to the B cell, causing activation of this B cell

Question 36

What are the last 3 stages of the humoral response?

Answer 36

4. Clonal expansion - activated B cell divides by mitosis to form plasma and memory cell clones 5. Cloned plasma cells produce and secrete the specific antibody which is complementary to the antigens on the pathogen’s surface, and these attach to antigens on pathogens and destroy them 6. Memory cells circulate the blood and tissue fluid, ready to divide if the body is re-infected by the same pathogen

Question 37

What is clonal selection?

Answer 37

The B cell with the correct antibody is selected for cloning

Question 38

What is clonal expansion?

Answer 38

The division of specific B cells to produce genetically identical clones

Question 39

What are the two types of immune response?

Answer 39

- primary immune response - secondary immune response

Question 40

What is the primary immune response?

Answer 40

Body is exposed to a pathogen for the first time so response is slow and infected individual experiences symptoms of the disease

Question 41

What is the secondary immune response?

Answer 41

Body has been exposed to the same pathogen before so response is much faster and stronger and pathogens are destroyed before any symptoms appear

Question 42

Describe the primary immune response

Answer 42

- the production of antibodies is slow after the first exposure to the pathogen - the concentration of antibodies increases slowly - because there are very few B cells that are specific to the pathogen’s antigens - takes time for B cells to divide into plasma cells to produce the correct antibody, so individual experiences symptoms of the disease - during this, some B cells divide into memory cells to make the individual immune to this disease

Question 43

Describe the secondary immune response

Answer 43

- production of antibodies is much quicker after exposure to pathogen - concentration of antibodies increases quickly - because memory cells recognise the pathogen’s antigens and quickly divide into plasma cells - plasma cells secrete larger numbers of antibodies to quickly destroy the pathogen before the individual experiences any symptoms

Question 45

What is the constant region on an antibody?

Answer 45

The same for all antibodies and binds to receptors on cells such as B cells

Question 46

What is the variable region on an antibody?

Answer 46

Different for each antibody as its shape is complementary to a specific antigen. This is the part that binds to antigens

Question 47

What are the three roles that antibodies carry out to help destroy pathogens?

Answer 47

- agglutination of pathogens - neutralisation of toxins - preventing pathogens from binding

Question 48

What occurs in the agglutination of pathogens?

Answer 48

Antibodies clump pathogens together to enable easier phagocytosis

Question 49

What occurs in the neutralisation of toxins?

Answer 49

Antibodies bind to toxins to inactivate them

Question 50

How do antibodies prevent pathogens from binding?

Answer 50

They bind to pathogens to stop them from infecting body cells

Question 51

What are monoclonal antibodies?

Answer 51

Antibodies produced from a single clone of plasma cells

Question 52

Give 4 uses of monoclonal antibodies

Answer 52

- diagnosis of disease (identify infected cells) - treatment of disease (as they bind to specific cells, bring therapeutic drugs with them) - pregnancy testing (bind to pregnancy hormone) - detecting certain cancers (bind to prostate specific antigens to identify prostatic cancer)