3.1.6 Immunology

Question 1

Where are leukocytes/white blood cells found?

Answer 1

Found in the blood, lymph, tissue fluid and body cavities.

Question 2

What are the four categories of leukocytes?

Answer 2

• Phagocytes
• Granulocytes
• T Lymphocytes
• B Lymphocytes

Question 3

Which categories of leukocyte are in the specific immune system?

Answer 3

T and B Lymphocytes

Question 4

What categories of leukocyte are in the non specific immune system?

Answer 4

Phagocytes and Granulocytes

Question 5

What is the non-specific immune system?

Answer 5

A collection of non-specific methods of destroying foreign bodies that have entered the body.

Question 6

Give two examples of the methods of the non specific immune system

Answer 6

Inflammation and Phagocytosis

Question 7

What leukocyte is responsible for inflammations and what does it do?

Answer 7

Granulocytes; they release histamine and prostaglandins

Question 8

Explain Inflammation

Answer 8

• Vasodilation occurs, causing the area to turn red
• capillaries leak so phagocytes and Granulocytes can reach local tissue. Area swells and the dead pathogens, phagocytes and excess tissue fluid are released as pus
• sensory neuron impulses are caused, making the area tender
• Blood clots to seal the wound, causing a scab to be formed

Question 9

What is phagocytosis?

Answer 9

The digestion of microbes and other foreign bodies by phagocytes

Question 10

What are phagocytes?

Answer 10

Large irregularly shaped leukocytes that have complex cytoskeleton that allows them to move and change shape

Question 11

What are the two branches of the immune system?

Answer 11

Specific and non-specific

Question 12

How does phagocytosis work?

Answer 12

When phagocytes crawling through blood reach microbes, they surround and engulf it, trapping the microbe in a membrane sac called a phagosome. This then fuses with lysosomes, releasing lysozymes which hydrolyse the proteins, carbs and lipids that make up the microbe, killing it

Question 13

What is the specific immune system?

Answer 13

A collection of reactions which involves the lymphocytes and which not only kill invading pathogens but also leaves a ‘memory’ of the pathogen so it can be neutralised in subsequent infections.

Question 14

What is the key feature of the specific immune system?

Answer 14

It is capable of self/nonself recognition; distinguishing foreign cells from its own, through use of antigens

Question 15

What is an antigen?

Answer 15

A large molecule on the outer surface of any living cell membrane or wall. Their purpose is for cell communication, and cells from different individuals have different antigens, as they are genetically controlled, so close relatives have more similar antigens to each other

Question 16

What are examples of antigens?

Answer 16

• Blood groups in red blood cells.

- Capsid proteins of viruses

Question 17

What are B-Lymphocytes? (B-Cells)

Answer 17

White blood cells which make antibodies.

Question 18

What is an antibody?

Answer 18

it is a protein molecule that can bind specifically to an antigen.

Question 19

What is the structure of antibodies?

Answer 19

4 polypeptide chains joined together by disulphide bonds to form a Y shaped structure.

Question 20

What is the stem of the Y in an antibody called?

Answer 20

The constant region; because it has the same amino acid sequence and structure in all immunoglobulins/antibodies

Question 21

What are the ends of the branches of the Y structure of an immunoglobulin/antibody called?

Answer 21

The variable region; because different immunoglobulin/antibodies have a different amino acid sequence and structure here.

Question 22

What are T Lymphocytes/T cells?

Answer 22

White blood cells that have receptor proteins in their surfaces.

Question 23

What are receptor proteins?

Answer 23

Very similar to antibodies, but only have one binding site and are only found on the surface of T cells. They bind with antigens to form antigen-receptor complexes.

Question 24

Explain Macrophage and Antigen presentation

Answer 24

Macrophages ingest nonself antigens by phagocytosis. When antigens pass to the surface of the macrophage, it becomes a antigen presenting cell. This amplifies the number of foreign antigens without increasing number of pathogens. Macrophage then secretes chemicals to stimulate clonal selection

Question 25

Explain clonal selection

Answer 25

Antigen presenting cells bind to helper T cells with a matching receptor. This stimulates cytokines release from the T cell, which stimulate immature T and B cells to activate, proliferate and differentiate. When they activate they divide rapidly by mitosis, creating an army of T and B cells with the binding sites that complement the foreign antigen.

Question 26

What happens after clonal selection?

Answer 26

The activated T cells differentiate into cytotoxic killer T cells, which bind to antigens on infecting pathogens, killing them by making pores in their membrane, causing them to burst as water diffuses in. This is called cellular immunity because foreign cells are killed directly by the lymphocyte cells.

Question 27

Explain humoral immunity

Answer 27

Activated B cells differentiate into plasma cells, which contain large amounts of RER, synthesising and secreting large amounts of soluble antibodies which are carried around blood, lymph and tissue fluid, binding to antigens and killing them in various ways.

Question 28

What are the various ways plasma cells kill antigens?

Answer 28

- Binding to antigens on viruses and bacteria, to prevent viruses and bacteria from attaching to other cells and infecting them - binding to free toxin proteins to change the shape of their active site so they cannot take part in disease causing reactions - causing agglutination

Question 29

What is Agglutination?

Answer 29

Where plasma cells link many cells together (because each antibody has 2 binding sites), immobilising viruses and precipitates soluble toxins so that they can be easily destroyed by phagocytes and killer T cells.

Question 30

Explain immunological memory

Answer 30

Some of the activated T and B cells differentiate into memory cells which remain in the blood for many years after the infection, and the memory B cells continue to release small quantities of antibody. This makes it quicker to identify and remove subsequent infections, as the memory cells will quickly divide to form a new clone army

Question 31

What is the primary immune response?

Answer 31

The slow and weak response to a first infection before memory cells have been created to quickly deal with it. When most symptoms are shown.

Question 32

What is antigenic variability?

Answer 32

When pathogens develop new strains, with new antigens that the body does not have memory cells against, prompting another primary response.

Question 33

How does vaccination work without making people sick?

Answer 33

The injection is made of non-virulent antigens, so they won't get sick but will still make memory cells in the primary response incase of a secondary infection.

Question 34

What is the secondary effect vaccine nation might have on immunity even on those who haven't been vaccinated?

Answer 34

Herd immunity; there are not enough hosts in which the pathogen can survive and reproduce so it won't even spread to non immunised people.

Question 35

What is active immunity and passive immunity?

Answer 35

Active: injecting antigens to promote primary response Passive: injecting antibodies into the blood of an already infected person.

Question 36

How is passive immunity naturally and artificially done?

Answer 36

Naturally; antibodies through breast milk and placenta to babies Artificial; injecting antibodies

Question 37

What are monoclonal antibodies?

Answer 37

Antibodies of a particular shape made by a clone of a single B cell

Question 38

How are monoclonal antibodies made?

Answer 38

- inject a mouse with antigens, which will show a primary immune response - extract B cells from mouse blood after a few days and dilute the blood into the wells of an immunoassay plate, one cell per well, - test each well for production of desired antibody

Question 39

How can monoclonal antibodies be used?

Answer 39

- to target drugs to specific cell in the body - to detect the presence of specific proteins - fluorescent antibodies can be used to stain particular organelles in microscope slides - passive immunity