Module 2 - Cell recognition and the immune system

Question 1

What are antigens?

Answer 1

A part of an organism that’s considered foreign to our immune system. They are proteins that stimulate an immune response.

Question 2

What are the following things that our body can detect with antigens?

Answer 2

Toxins
Pathogens
Cells from other organisms in the same species

Question 3

What are the types of immune systems?

Answer 3

Specific: B and T lymphocytes

Non-specific: Phagocytosis by phagocytes

Question 4

Where are phagocytes contained within the body?

Answer 4

Tissue and in the blood

Question 5

Explain the process of phagocytosis

Answer 5

Phagocyte contains receptors which bind to the antigens on pathogen. Phagocyte changes shape then surrounds and engulfs the pathogen. Once engulfed, the structure becomes a phagosome vesicle. A lysosome within the phagocyte will fuse with phagosome and release contents. Contains enzyme called lysozyme which is released into phagosome which hydrolyses pathogens.

Question 6

What happens with the destroyed pathogen after it has been hydrolysed?

Answer 6

Soluble products are absorbed and used by the phagocyte.

Question 7

2 differences between specific mechanisms and non-specific mechanisms

Answer 7

Specific respond slow, non-specific responds quickly.

Specific distinguishes between different pathogens, non-specific treats all pathogens in the same way.

Question 8

Describe how phagocytosis of virus leads to presentation of its antigens

Answer 8

Vesicle fuses with the lysosome. Lysosome releases hydrolytic enzymes. Antigens from virus are displayed on the cell membrane.

Question 9

What gets activated after Phagocytosis occurs?

Answer 9

Antigens on phagocytes bind to specific receptors on the surface of T cell. This activates T helper cells

Question 10

What do T helper cells activate?

Answer 10

Phagocytes, T cytotoxic cells and B cells

Question 11

Decsribe the cellular response

Answer 11

• APC- phagocyte, cancer cell
• T helper cell binds to APC
• cytokines released and stimulate T cells
• Triggers mitosis and differentiation of T cells (clonal selection)
• Into T helper cells and cytotoxic cells which releases perforin- destroys infected cells
• Osmotic lysis
• Only suitable when pathogen are inside host cell

Question 12

What are cytotoxic T cells?

Answer 12

These release toxins that bind to to and kill foreign cells or abnormal cells in the body

Question 13

Describe humoral response

Answer 13

• T helper cell recptor binds to APC
• Cytokines released and stimulate B cells and phagocytes to undergo mitosis and differentiation of B cells into B plasma cells and B memory cells
• B plasma cells produce and secrete mononclonal antibodies
• Antibodies bind to pathogen antigens- antigen/antibody complex
• Agglutination
• Increases efficiency of phagocytosis
• This is primary respone…. secondary response= memory cells- rapid antibody production

Question 14

Describe the activation of B cells

Answer 14

Selection of B cell with complementary receptor to antigen is clonal selection. Correct B cell selected causes it to divide multiple times to produce identical plasma cells. These make antibodies. Clonal expansion.

Question 15

Explain how an antigen-antibody complex is formed.

Answer 15

B cells have antibodies on their cell surface which is complementary to a specific antigen. This antigen bind to the antibody forming an antigen-antibody complex.

Question 16

What is agglutination?

Answer 16

This is where pathogens are clumped together. The pathogens are engulfed by phagocytes via phagocytosis and then pathogens are destroyed.

Question 17

What are monoclonal antibodies?

Answer 17

Antibodies are proteins that are produced by plasma cells during the immune response. These are called monoclonal antibodies.

Question 18

Describe the main regions in antibodies

Answer 18

Variable regions bind to specific antigens. One antibody to 2 antigens allowing these to clump together in agglutination. Constant regions remain the same in every antibody. Heavy chains connect both regions with hinge proteins. Heavy chains bind to light chains with disulphide bridges

Question 19

What are the 2 uses of monoclonal antibodies?

Answer 19

Targeted medication and Medical diagnosis.

Question 20

What is targeted medication?

Answer 20

cancer cells have antigens that signal as abnormal cells. Monoclonal antibodies can be used to bind specifically to antigens on cancer cells. Cancer treatment can be harmful so binding specifically means it can reduce damage to other cells

Question 21

What is medical diagnosis?

Answer 21

Antibodies are attached to dye, fluorescent or radioactive marker. If antigens are present, complementary antibody will bind and marker will become visible.

Question 22

What is the ELISA test, briefly explain (full detail in immune system notes).

Answer 22

1) Antigen of infection is at bottom of beaker.
2) Blood sample added. Blood containing antibodies complementary to antigens then this forms antigen-antibody complexes.
3) Beaker is washed so unbinded antibodies removed.
4) Secondary antibodies added with enzyme bound. If this binds to other antibodies, colour changes.
5) solution reacting with enzyme is added
6) Colour change indicates secondary antibodies bound to antibodies from blood and so indicated blood is infected wit pathogen.

Question 23

What is the primary response and symptoms shown?

Answer 23

Is slow because takes time for antigens to be detected and specific plasma cells to be activated. Person shows signs of pathogens as it has time to cause harm before removed from immune system

Question 24

What are memory cells?

Answer 24

T cells and B cells produce memory cells after an infection. These remain in body after infection has been removed. These quickly identify antigens and produce correct antibodies. Stronger because plasma cells can be produced more quickly.

Question 25

Secondary immune response and symptoms shown

Answer 25

Rapid because of memory cells as it detects antigens and produces correct antigens. Plasma cells produced quicker. Unlikely to show symptoms as individual is immune

Question 26

Describe briefly how vaccines work?

Answer 26

Weakened or dead pathogen inserted. Primary response leads to production of memory cells. Provides immunity. Booster vaccination can be given to ensure memory cells are still contained in body.

Question 27

Describe how a vaccine leads to the production of antibodies

Answer 27

• Vaccine made up of dead or inactive pathogens
• Phagocyte present antigen on its service
• T cell with complementary recptor binds to antigen
• T cell stimulates Bcells, with complementary antibody on its surface
• B cells (plasma) secretes large amount of antibodies
• B cell divides to produce same antibodies

Question 28

Why are some vaccines constantly being changed?

Answer 28

Antigens are evolving at a very rapid rate. They avoid to prevent detection by immune system sometimes making vaccines useless.

Question 29

What is herd immunity?

Answer 29

Only works if majority of the population is vaccinated reducing chances of someone becoming infected with disease.

Question 30

What is active immunity and explain the 2 types.

Answer 30

This is where the immune system has created its own antibodies.
Natural - Antibodies have been created in response to the disease
Artificial - Antibodies have been created in response to vaccination of antigens

Question 31

What is passive immunity and explain the 2 types

Answer 31

This is where an individual receives antibodies from an external source.
Natural - Antibodies given to babies through breast milk
Artificial - Antibodies given via injection

Question 32

Describe the structure of HIV

Answer 32

Inside is a protein called the capsid containing 2 RNA strands and integrase and reverse transcriptase.
Viral envelope containing lipid bilayer and glycoproteins

Question 33

Briefly explain the process of HIV

Answer 33

• Attachment proteins attach a helper T cell
• RNA enters cell
• Reverse transcriptase converts RNA to DNA
• Viral proteins produced
• Viral proteins assembled and released from cell

Question 34

Symptoms of AIDS

Answer 34

Mid-flu (short-term).

Overtime HIV virus particles become active and destroy helper t cells

Question 35

Treatments of AIDS

Answer 35

No current cure for AIDS but high level of medical care can maintain life expectancy.

Question 36

What are antibiotics and viruses?

Answer 36

Commonly kill bacteria by interfering with the metabolism of bacterial cells whilst others prevent protein synthesis
Viruses are particles so they have no metabolism or cell structure for antibiotics to act and disrupt on

Question 37

Uses or monoclonal antibodies in targeting cancer cells

Answer 37

Direct: antibodies bind to antigens, hormone that stimulates cancer cell growth cannot communicate therefore preventing cell replication as antibody blocks it.
Indirect: Antibodies with cytotoxic drug attached binds to the antigen. Drug destroys cell.

Question 38

Uses of monoclonal antibodies for medical diagnosis give e.g.

Answer 38

Diagnostic for influenza, hepatitis and chlamydia for rapid result.
Men with prostate produce more of protein, prostate specific antigen. Using antibodies, it is possible to obtain a measure of the level of PSA in blood

Question 39

Uses of monoclonal antibodies in pregnancy testing

Answer 39

Women produces more of human chorionic gonadotrophin. Antibodies on both ends of test strip. One side a blue dye is added, other side has nothing. If HCG is present it will bind to antibodies with dye. This travels to t other end where these antibodies also bind forming colour to appear.

Question 40

3 ethical issues

Answer 40

Injecting mice with cancer to get tumour cells
Treated people with cancer and diabetes but killed people with MS
Trials can mean development of health implications or death.