Week 3 - Adaptive Immunity

Question 1

Define Immunity

Answer 1

Capacity of the immune system to successfully defend the body against a potentially infectious agent

Question 2

What cells are involved in adaptive immunity?

Answer 2

Lymphocytes

Question 3

What are the 2 types of lymphocytes?

Answer 3

• B cells

- T cells

Question 4

Where do both types of Lymphocytes originate from?

Answer 4

Stem cells in bone marrow

Question 5

What is an Antigen?

Answer 5

Any substance that the body recognises as foreign, or non-self

Question 6

Name the two categories of adaptive immunity

Answer 6

• Anti-body mediated immunity

- Cell-meditated immunity

Question 7

Describe ‘Anti-body meditated immunity’

Answer 7

• This response activates B-cells that then proliferate and produce:
  - Plasma cells
  - Memory cells
• Involves the activation of B cells and secretion of antibodies when in contact with a pathogen.
• Produces antibodies to destroy microbes

Question 8

Describe ‘Cell-meditated immunity’

Answer 8

• Destroys infected cells

- Immune response that does not involve antibodies.

Question 9

What cells are involved in ‘anti-body meditated immunity’?

Answer 9

• B cells
• Plasma
• Memory

Question 10

What cells are involved in ‘cell-meditated immunity’?

Answer 10

• T cells

- Memory-T cells

Question 11

How do B cells provide immunity?

Answer 11

Fight bacteria and viruses by making Y-shaped proteins called antibodies, which are specific to each pathogen and are able to lock onto the surface of an invading cell and mark it for destruction by other immune cells

Question 12

How do Plasma cells provide immunity?

Answer 12

Produce antibodies which circulate in the blood and other body fluids which target bacteria and their toxins and prepare them for destruction, also target viruses before they enter body cells

Question 13

How do Memory cells provide immunity?

Answer 13

Persist in the body for months - years and can react with the same antigen again if it enters the body at a later date

Question 14

How do T cells provide immunity?

Answer 14

Destroy cells that harbour viruses or bacteria and cancer cells and parasites. They fight intracellular pathogens

Question 15

How do Memory T cells provide immunity?

Answer 15

Specifically produced to the microbe

Question 16

Where does ‘anti-body meditated immunity’ occur?

Answer 16

In the bone marrow

Question 17

Where does ‘cell-meditated immunity’ occur?

Answer 17

In infected cells

Question 18

What is the primary immune response?

Answer 18

Response of the immune system the first time it is exposed to a particular antigen. There is a lag period 5 – 7 days in which there’s no increase in the level of antibodies in the blood.

Question 19

What is the secondary immune response?

Answer 19

Due to increased numbers of specific memory cells which are more easily stimulated to produce plasma cells which produce antibodies. The memory cells provide immunological memory.

Question 20

Why is the secondary immune response important?

Answer 20

Causes the many memory cells to rapidly produce new plasma cells & large numbers of antibodies within a few days. Possessing memory cells & the capacity to produce a rapid secondary response means that a person is immune to that specific antigen.

Question 21

What are the 4 classes on antibodies?

Answer 21

• igG
• igA
• igM
• igE

Question 22

What are some features of igG class?

Answer 22

• Protect against bacteria, neutralise toxins and viruses, trigger complement, make phagocytosis more effective.
• The longest-lasting of the antibodies in the blood
• Can cross the placenta so foetus and new-born get some protection from mother.

Question 23

What are some features of igA class?

Answer 23

• Most common antibody in secretions and on mucus membranes
• Bind antigens before they invade tissues and prevent microbes adhering to mucus membranes - especially in respiratory system
• Most abundant antibody in the body

Question 24

Name some examples of mucus membranes

Answer 24

• Breast milk
• Saliva
• Tears

Question 25

What are some features of igM class?

Answer 25

- First type to be produced when antigen is encountered - Lasts only a short time therefore presence of these indicates a very recent or current exposure to the antigen - Very good at clumping antigen, and triggering complement

Question 26

What are some features of igE class?

Answer 26

- Tiny amounts only - Involved in allergic reactions - Bind to mast cells and basophils which release histamine when antigen binds to igE

Question 27

Name and describe the 4 functions of antibodies

Answer 27

1. Enhance phagocytosis. Antibodies coat the microbe making it easier for the phagocyte to recognise & ingest the microbe. 2. Activates complement. When the antibody connects to the antigen it changes shape exposing a section of the antibody where complement proteins can bind. Complement is activated. 3. Neutralisation: Antibodies bind to & block the attachment sites on the microbe to stop it binding to the host cell. 4. Agglutination into large complexes so reduces the number of infectious units phagocytes have to deal with.

Question 28

Describe the role of major histocompatibility complex (MHC)

Answer 28

To prevent the immune system from attacking our own cells. We have proteins on the surface of our cells which identify us as self

Question 29

How do T cells destroy infected cells?

Answer 29

A cell infected by a virus or bacterium displays microbial antigen fragments on its surface. The cytotoxic T cell binds to the infected cell and inserts perforin proteins into the cell membrane, which injects enzymes which kill the cell. This stops the virus multiplying and exposes it to antibodies outside the cell. Memory T cells specific to the microbe are produced

Question 30

What are antibodies also known as?

Answer 30

Immunoglobulins