Immunology

Question 1

Give 5 types of molecules that cell surface molecules identify

Answer 1

Pathogens

Cells from other organisms of the same species (transplants)

Abnormal body cells (e.g. cancerous cells)

Cells infected with viruses

Toxins

Question 2

Define an antigen

Answer 2

A foreign protein (or glycoprotein) that stimulates the production of antibodies

Question 3

What is another word for phagocytosis

Answer 3

The non-specific response

Question 4

Outline phagocytosis

Answer 4

1) The receptors on the phagocyte bind to the specific ,complimentary antigens on the phagocyte

2) The phagocyte engulfs the pathogen, forming a vesicle called a phagosome.

3) A lysosome binds to the phagosome, and releases lysozymes and other hydrolytic enzymes. The lysozymes and other hydrolytic enzymes destroy the pathogen

4) The cell becomes an antigen presenting cell, where antigens from the bacteria/virus is presented on the cell surface membrane

Question 5

Give one type of genetic drift

Answer 5

Antigenic variability

Question 6

Explain how antigenic variability occurs and what it causes

Answer 6

Mutations in the viral genetic material can alter the tertiary structure of the antigens, allowing it to bind to different receptors.

When this occurs, the pathogen’s antigen will not be recognised by the memory cells from the primary response as the antigen is no longer complimentary to receptors and the individual will not be able to initiate a secondary response.

This makes it difficult to develop vaccinations against these disease causing pathogens

Question 7

What is another name for the cellular response

Answer 7

The cell mediated response

Question 8

What is the response of T lymphocytes to a foreign antigen called

Answer 8

The cellular response

Question 9

Outline the cellular response

Answer 9

1) Receptors on the T-cell bind to the specific , complimentary antigens on the antigen-presenting cells, causing the T-cell to divide rapidly by mitosis (clonal expansion)

2) These cloned T cells:

• Differenciate into memory T cells to enable a rapid response to reinfection of the same pathogen,
• Stimulate (using cytokines) Cytotoxic T cells, which release an enzyme called Peforin which creates pores (holes) in the cell membrane. This allows substances to move into the cell, causing cell death

-Differenciate into Helper T cells, which stimulate B cells to divide by mitosis producing many clones. These cells then differentiate into memory B cells (which can respond and release antibodies more rapidly on reinfection with the same antigen) and Plasma cells (which secrete antibodies). T cells also stimulate phagocytosis of pathogens.

Question 10

How do helper T use their chemicals that they release

Answer 10

Helper T cells release chemicals called cytokines that attract phagocytes and B cells to the area of infection

Question 11

What is the name of the response that involves the response of B lymphocytes to a foreign antigen, clonal selection and the release of monoclonal antibodies

Answer 11

The humoral response

Question 12

Outline the humoral response

Answer 12

There are 2 ways the B cells can be stimulated:
1-An antigen is presented by a phagocyte/macrophage (antigen presenting cell) to a helper T lymphocyte, and the antigens bind to the t cells complimentary receptors,
The helper T cell secretes Cytokines which activates the specific, complimentary B cell (CLONAL SELECTION)

2- The B cell binds directly to the antigen presenting cell via it’s specific and complimentary receptors, triggering the B cell.

The B cell is stimulated to divide by mitosis, producing many clones (CLONAL EXPANSION)

These clones then differentiate into cell types:
-Plasma cells which secrete specific antibodies to the antigen (they only survive for about 5 days)
-Memory cells which remain in the body to give rapid response to the pathogen should there be future re-infection (these can survive all your life).

Question 13

What is antigenic variability and why this makes it difficult to develop vaccinations against these disease causing pathogens

Answer 13

This is a type of genetic drift. Mutations in the viral genetic material can alter the tertiary structure of the antigens (or viral attachment proteins), allowing it to bind to different receptors (e.g other cell types).

When this occurs, the pathogen’s antigen will not be recognised by the memory cells from the primary response, as the antigen is no longer complimentary to the receptors and the individual will therefore not be able to initiate a secondary response.

This makes it difficult to develop vaccinations against these disease causing pathogens.

Question 14

Define an antibody

Answer 14

A protein (immunoglobulin) specific to an antigen, secreted by plasma cells

Question 15

Outline the structure of an antibody

Answer 15

They are proteins with quaternary structures that are made from 4 polypeptide chains- 2 light and 2 heavy chains, with 2 variable binding regions, each with specific tertiary structures that are complimentary to one specific antigen, at the top and a constant region at the bottom. These chains are held together by disulfide bridges.

Question 16

Draw and label the structure of an antibody

Answer 16

Question 17

Outline the function of the formation of antigen-antibody complexes

Answer 17

The formation of an antigen antibody complex leads to the destruction of the antigen. One method Is agglutination:

Antibodies (which act as markers for phagocytosis) can bind to antigens on multiple pathogens simultaneously, causing clumping (agglutination) of the pathogen. They attract the phagocytes and make it easier for them to engulf and hydrolyse all the pathogens.

Question 18

Outline and explain differences in the primary and secondary immune response (NOT COMPLETED)

Answer 18

The primary immune response occurs when you are infected with a pathogen for the first time, and the secondary response occurs when you are re-infected with the same pathogen in the future.

Primary response is slow because it takes time for the correct B cell to be activated (clonal selection) and divide then differentiate into lots of plasma cells (clonal expansion) to produce antibodies (NOT COMPLETED)

Question 19

Outline and explain differences between the primary and secondary immune responses

Answer 19

The primary immune response occurs when you are infected with a pathogen for the first time, but the secondary immune response occurs if you are re-infected with the same pathogen again.

The primary immune response is slow because it takes time for the correct B cell to be activated (clonal selection) and divide then differentiate into lots of plasma cells (clonal expansion) to produce antibodies with a complimentary shape to the antigen.
However, the Secondary response is much quicker because the correct T and B memory cells will immediately recognise the antigen and start dividing.

During the primary response, you will experience symptoms as it takes time for the pathogen to be killed. However, during the secondary response, the pathogen is destroyed so quick that you don’t experience symptoms - you are immune.

Question 20

What do the T memory cells and B memory cells do in the secondary response

Answer 20

The T memory cells will divide into the correct type of T killer cell to kill any infected cells

The B memory cells will divide into plasma cells to produce many antibodies which are complimentary to the antigen on the pathogen

Question 21

Describe 3 differences in the primary and secondary response shown here

Answer 21

The primary response (after the first infection) has a more delayed response time, with a slow rise in antibody concentration. However the Secondary response is much faster with a more rapid ride in antibody concentration.

The primary response produces a much lower concentration of antibodies than the secondary response.

The secondary response declines more quickly after reaching it’s peak, whereas the secondary response maintains a higher concern of antibodies for a longer period , providing a stronger immunity

Question 22

Explain how falling vaccination rates can be bad

Answer 22

Less people getting vaccinated against a disease can lead to a loss of herd immunity, as it increases the likelihood of the diseased people encountering non vaccinated people. This leads to lots more people being effected by the disease

Question 23

Outline how vaccinations can rate immunity

Answer 23

Inactive or dead pathogens or sometimes just antigens from the pathogen are injected into the persons body.

This antigen is displayed on the surface of antigen presenting cells (macrophages in the cellular response or B cells in the humoral response)

A specific helper T cell with the complimentary receptor protein binds to the antigen and activates a specific B cell (also with the correct receptor/antibody on its surface) using cytokines

The B cell divides by mitosis to form many clones, which differentiate into plasma and B memory cells.

The plasma cells produce large amounts of antigen against that specific antigen that fight it.

The B cells remain in the body for long periods, and can quickly produce plasma cells and antibodies upon future infections with the same antigen

Question 24

Give 2 reasons why some vaccines are given multiple times

Answer 24

1) to produce more memory cells, so there is a higher concentration of antibodies in the blood and they are produced faster upon further infection

2) some pathogens can carry out antigenic variability, do new vaccinations with the correct shape antigens must be repeated to keep the B cell antibodies complimentary to the antigens

Question 25

In simple terms, explain what active and passive immunity is

Answer 25

Active immunity involves the production of antibodies and memory cells by the patients own immune system Passive immunity involves introducing antibodies from another source.

Question 26

What are the 2 types of active and passive immunity

Answer 26

Artificially acquired and naturally acquired

Question 27

Give one naturally required way to get active immunity

Answer 27

Antigens enter the body naturally and the body produces it's own antibodies and specialised lymphocytes

Question 28

Give one naturally acquired way to get passive immunity

Answer 28

Antibodies pass from the mother to the fetus via placenta or to the infant via breast milk

Question 29

Give 1 artificially acquired way to get active immunity

Answer 29

Antigens are introduced by vaccinations, and the body procured antibodies and specialised lymphocytes

Question 30

Give 1 artificially acquired way to get passive immunity

Answer 30

Preformed antibodies in an immune serum are introduced by injection

Question 31

Explain how we can treat venomous snake bites . What type of immunity is this, and why is it needed

Answer 31

Antivenom is injected into the body. This contains antibodies against the snake toxin, which will bind to the toxin and target it for destruction. This is a type of artificially acquired passive immunity, and is needed because active immunity is too slow In this instance

Question 32

Give 4 differences between active and passive immunity

Answer 32

Active immunity involves memory cells production, but passive immunity doesn't. Active immunity involves plasma cell and antibody production, but passive immunity doesn't involve plasma cell and antibody production - antibodies are introduced into the body from an outside source Active immunity is long term, as the memory cells specific to the antigen remain. However, passive immunity is short term because there are no memory cells and the antibody given is destroyed by the body Active immunity can take a long time to develop but passive immunity is fast acting

Question 33

What is the role of plasma cells in producing primary and secondary immune responses

Answer 33

Plasma cells secrete antibodies that are specific and complimentary to the pathogens antigen during both the primary and secondary response

Question 34

Give the role of memory cells in producing primary and secondary immune responses

Answer 34

Memory B cells are useful in the secondary response - they can respond and release plasma cells more rapidly on re-infection with the same antigen Memory T cells are also used in the secondary response - they can respond and differentiate into the correct T helper and T killer cells rapidly on re-infection with th same antigen

Question 35

Outline how a vaccine can create immunity to a disease

Answer 35

The vaccine, containing antigens from the pathogen, is injected into the body This antigen is displayed on the surface of antigen presenting cells (macrophages in the cellular response or B cells in the humoral response) A specific helper T cell with the complimentary receptor protein binds to the antigen and releases cytokines, activating a specific B cell (also with the correct receptor on its surface for that antigen). The B cell dives by mitosis to form many clones, which differentiate into plasma and memory B cells. The plasma cells produce large amounts of antibodies against that specific antigen The memory B cells can produce the correct plasma cells which secrete the complimentary antibodies more rapidly upon future infection with the same antigen, fighting the pathogen before the person gets the disease. This person is now immune If most people are vaccinated, herd immunity occurs which protects the non-vaccinated people too as there's less people to spread the disease

Question 36

How can falling vaccination rates lead to a loss of herd immunity

Answer 36

It increases the likelihood of diseased people encountering non vaccinated people

Question 37

Why are some vaccines given more than once

Answer 37

So there's a higher concentration of antibodies in the blood, and they are produced rapidly upon further infection

Question 39

Draw and label the structure of HIV. What does HIV stand for?

Answer 39

HIV= Human Immunodeficiency Virus

Question 40

Outline HIV replication

Answer 40

Attachment proteins on HIV attach to receptors on CD4 helper T cells The HIV RNA is converted into DNA using reverse transcriptase. The HIV DNA is inserted into the helper T cell DNA and is transcribed into HIV mRNA. The HIV mRNA is translated into new HIV proteins and assembled into viral particles, which are then released from the cell.

Question 41

Explain how HIV causes the immune system to be damaged

Answer 41

The HIV infects helper T cells known as CD4 cells. When the levels of these cells decreases as they are destroyed, and the viral load increases, a patient is said to have developed AIDS. The description of the helper T cells means fewer/no B cells will be activated to undergo mitosis and Differentiate into plasma cells, meaning less or no antibodies are produced. This means pathogens can't be destroyed

Question 42

Explain why antibiotics are ineffective against viruses

Answer 42

1) Antibiotics kill bacteria by targeting bacteria specific enzymes or organelles. They are ineffective against viruses due to viruses using the host's machinery to replicate, as viruses are acellular. 2) Some antibiotics work by destiny the links in the peptidoglycan cell walls of bacteria, making them more susceptible to osmotic lysis, hence killing them. Viruses don't have a peptidoglycan wall, so antibodies can't destroy them. 3) some antibiotics also inhibit DNA Replication. If a virus is a retro virus, there is no DNA to replicate (as it has RNA instead)

Question 44

What is the Eliza test

Answer 44

A way to detect either antigens or antibodies in a patient's bodily fluids, using monoclonal antibodies.

Question 45

Outline how the Eliza test can be used to detect antigens in a patients blood

Answer 45

Antibodies which are complimentary to the antigen immobilised on the surface of the test well A test sample is added and if the corresponding antigen is present, it attaches to the immobilised antibodies. When an enzyme-labeled antibody is added, it binds with the complimentary antigen. The well is rinsed to ensure there are no free enzyme labeled antibodi es. An enzyme substrate is added. The enzyme substrate reacts with the enzyme. This causes a colour change that is proportional to the amount of antigen present.

Question 46

What are monoclonal antibodies?

Answer 46

Antibodies with the same tertiary structure, produced from clones of the same plasma cell