The Immune System - Adaptive Immune System (w11)

Question 1

What MHC class is a T helper cell ?

Answer 1

MHC class II (antigen presenting)

Question 2

What are the 5 effects of antibodies ?

Answer 2

1) Inactivate antigen: antibody binds to an antigen or when many antigens are bound together

2) Activates Complement Cascade: Antigen binds to antibody. Antibody can then activate complement proteins causing inflammation, attracts WBC and lyses cells

3) Initiates release of inflammatory mediators: Antibody binds to mast cell /basophil. Triggers degranulation

4) Facilitate Phagocytosis: Antibody binds to antigen. Macrophages attaches to Fc of the antibody and phagocytoses both the antibody and the antigen

5) Antibody dependent cellular activity : Activates cytotoxic cell responses. Cytotoxic cells release chemicals that destroy the antibody-bound antigen

Question 3

Antigens are …

Answer 3

• foreign substances introduced into body
• molecules produced by body
• stimulate an adaptive immune response

Question 4

How does the secondary antibody response differ from primary ?

Answer 4

Is quicker to produce antibodies

Question 5

Do APC have MHC I complex or MHC II complex ?

Answer 5

MHC II complex

Question 6

What is the function of cytotoxic T cells ?

Answer 6

1) They release cytokines.
- this attracts the innate immune cells, macrophages, phagocytes of antigen/ cell and causes the inflammatory response.
- it also activates additional cytotoxic T cells.

2) directly kill the virus infected cells
- viral antigens on surface
- the T cells bind to the antigens on the surface and causes the cells to lose of under go apoptosis

Question 7

Define allergen …

Answer 7

An antigen that is typically not harmful to the body

Question 8

What is an allergic response ?

Answer 8

An immune response to a non-pathogenic antigen

Question 9

What is the sensitisation phase equivalent to ?

Answer 9

The primary immune response

Question 10

What type of antibodies are produced during the allergic response ?

Answer 10

IgE and IgG

Question 11

What role do IgE antibodies play in the allergic response ?

Answer 11

• IgE antibodies immediately bind to the mast cells and the basophils, this then forms memory T and memory B cells

Question 12

What happens when an individual is re-exposed during the allergic response ?

Answer 12

The allergen binds to the IgE already present on the mast cells, this triggers the immediate release of histamines, cytokines and other mediators.
This then causes allergic symptoms which brings around a rapid response

Question 13

Describe lymphocyte proliferation (first step in immune response, HINT: B cell) …

Answer 13

1) Before a B cell can be activated by a T helper cell the B cell receptor has to bind to the antigen, this complex is then taken into the B cell by endocytosis.
2) The B cell then uses and MHC class II molecule to present the processed antigen to the T helper cell.
3) The T cell receptor then binds to this MHC class II/ antigen complex.
4) CD4 costimulates the B cell and other surface molecules
5) there is also costimulation by interleukins (cytokines) which are released from the helper T cell.
6) The B cell then divides, this results in daughter cells dividing and so on, producing many cells which all recognise the same antigen.
7) Many of these daughter cells differentiate to become plasma cells, which go on to produce antibodies. These are part if the overall immune response which eliminate antibodies

Question 14

What do helper T cells help with ?

Answer 14

The activation of B cells and other T cells to be activated

Question 15

What does an antibody consist of ?

Answer 15

• consists of four polypeptide chains :
• 2 light chains
• 2 heavy chains
  -antigen binding site

Question 16

What is an IgM immunoglobulin ?

Answer 16

• e.g. Pentamer
• it is involved in the primary immune response

Question 17

What is a IgG immunoglobulin ?

Answer 17

• e.g. a monomer
• it is involved in the secondary immune responses
• some maternal IgGs are capable of crossing the placental membrane

Question 18

What is a IgA immunoglobulin ?

Answer 18

• e.g. a secretory IgA dimer
• used in external secretions, this can be found in the saliva, tears, bronchial mucus and breast milk.

Question 19

What is a IgE immunoglobulin ?

Answer 19

• e.g. a monomer
• these target parasites found in the gut and are associated with the allergic response

Question 20

What happens during the proliferation of cytotoxic T cells, using the example of the invasion of a virus …

Answer 20

1) The virus infects the cells.
2) This means that some of the viral proteins are broken down and become processed by antigens.
3) this then gets combined with MHC class I molecules, as is displayed on the surface of the infected cell.
4) T cells are then activated by the T cell receptor binding with the MHC class I / antigen complex.
5) the surface molecule CD8 then causes co-stimulation.
6) This then stimulates T cells to divide.

Question 21

What is active immunity ?

Answer 21

Immunity that is provided by the individuals own immune system

Question 22

What is passive immunity ?

Answer 22

Immunity that is transferred from another person or an animal

Question 23

What is natural active immunity ?

Answer 23

When the antigens are introduced through natural exposure

Question 24

What is artificial active immunity ?

Answer 24

When the antigens are deliberately introduced via a vaccine

Question 25

What is natural passive immunity ?

Answer 25

When the antibodies from the mother are transferred to her child across the placenta or in the milk

Question 26

What is artificial passive immunity ?

Answer 26

When the antibodies are produced by another person or an animal and are injected

Question 27

What are some bad effects the aging immune system causes ?

Answer 27

• antibody and cell mediated responses decrease
• primary and secondary antibody responses decrease
  (Overall the immune system becomes less efficient with age)