Specific response 4.1.6

Question 1

What are antigens?

Answer 1

All cells have antigens (specialised glycolipids and glycoproteins) on their surface
The host body recognise antigens as self or foreign, if they’re foreign the immune response will be initiated

Question 2

What is the immune system controlled by?

Answer 2

White blood cells (lymphocytes

Question 3

What is the scientific name for white blood cells?

Answer 3

Lymphocytes

Question 4

What are the two main types of lymphocytes?

Answer 4

B lymphocytes - formed in bone marrow
T lymphocytes - formed in thymus

Question 5

Describe the humeral response (plasma cells)

Answer 5

• Pathogen invades
• Macrophage ingests pathogen and displays antigens on membrane
• B cell activated by helper T cell (by interleukins) and antigens on macrophage, multiply by mitosis and differentiate
  EITHER!!!!! :
  Plasma cells- secrete specific antibody and are transported by blood/lymph (only survive a few days) and an antigen-antibody complex is formed)
  Memory B cells - continue to secrete antibody for years, they also reproduce rapidly, producing plasma cells if the same pathogen invades again

Question 6

What is clonal expansion?

Answer 6

The division of B cells to produce many different B cells, including clones of plasma and memory cells, made by mitosis.

Question 7

What do plasma cells do?

Answer 7

They produce and secrete antibodies into blood stream - however only live for a few days.
These cloned plasma cells produce specific complimentary antibodies to bind to the pathogens antigen, disabling them, or causes agglutination or neutralisation

Question 8

What do memory cells do?

Answer 8

They remain in lymph nodes to respond rapidly if the same type of pathogen invades again

Question 9

What is clonal selection? (basic)

Answer 9

Involves secreting the correct antibody for cloning

Question 10

What is an antibody?

Answer 10

A protein made by a B lymphocyte in response to an antigen

Question 11

Describe in detail what antibodies are

Answer 11

They are specialised glycoproteins called immunoglobins.
These are specific and bind to only one type of antigen, through a ‘lock and key’ model basis
The variable regions are different in every antibody, complimentary to that of the shape of the antigen.

Question 12

What is formed when an antigen binds to an antibody?

Answer 12

An antigen-antibody complex

Question 13

What is the constant region in an antibody?

Answer 13

It is the same in all antibodies, and has a site where it can bind to receptors on immune system cells

Question 14

What is the heavy chains function in the antibody?

Answer 14

Contains the site at which the antibody can bind to a cell

Question 15

What is the function of the hinge region in the antibody?

Answer 15

It allows flexibility when the antibody binds to the antigen

Question 16

How many antigen binding sites are in each antibody?

Answer 16

2 - meaning it can bind to more than one pathogen at once to agglutinate them (clump)

Question 17

What are three ways that antibodies can help to defend the body against pathogens

Answer 17

Agglutinins - agglutinate and bind to receptors on pathogens to prevent them from entering host cells
Opsonins - act as markers for phagocytes
Antitoxins - neutralise toxins

Question 18

What are the 3 types of antibody?

Answer 18

Opsonins
Agglutinins
Anti-toxins

Question 19

What are opsonins?

Answer 19

They are antibodies that bind to antigens and act as markers for phagocytes

Question 20

What are agglutinins?

Answer 20

They bind to antigens and cause clumping - prevents them entering body cells. It also makes pathogens more easily engulfed by phagocytosis

Question 21

What are anti-toxins?

Answer 21

Bind to toxins to prevent harm to human cells. Phagocytes then engulf the ‘toxin-antibody’ complexes

Question 22

How do antibodies work?

Answer 22

1. Antibody-antigen complex acts similar to the opsonin chemical, by stimulating the digested by phagocytosis
2. Most pathogens cannot affect the bodies cells once they formed an antibody-antigen complex

Question 23

What is neutralisation?

Answer 23

Antibodies can act as antitoxins, binding with toxins produced by pathogens. This makes them harmless

Question 24

What is humeral immunity by definition?

Answer 24

Is a response to pathogens found in the bloodstream, mainly bacteria and fungal infection.

Question 25

Are antibodies soluble, and if so, where?

Answer 25

They are produced to be soluble in the blood, tissue fluid and lymph fluuid

Question 26

What lymphocyte is more important in humeral immunity?

Answer 26

B cells

Question 27

Describe B cells

Answer 27

They have different antibodies on their surface, and will bind to the complementary antigens on the pathogens membrane. The B cell will engulf the pathogen and present the antigen on its surface, becoming an antigen-presenting cell

Question 28

What is cell-mediated immunity?

Answer 28

It is a response to cells that have been infected by a pathogen, mainly viruses. 1. Macrophages engulf and digest pathogens by phagocytosis - they present the antigens on the surface 2. Specific T helper cell with receptor that fits the antigen on the macrophage will bind. The T helper cell will produce interleukins which stimulate more T cells to be produced 3. Cloned T cells may become, more T helper cells (to produce more interleukins), killer T cells, or T memory cells to destroy infected pathogens

Question 29

What are 4 types of T cells (explain)

Answer 29

T helper cells - release cytokines that stimulate B cells to develop. It also stimulates phagocytes and phagocytosis T killer cells - attack and kill host-body cells that display the foreign antigen T memory cells - provide long-term immunity T regulator cells - shut down the immune response once the pathogen has been removed

Question 30

What are T helper cells?

Answer 30

Release cytokines that stimulate B cells to develop. It also stimulates phagocytes and phagocytosis.

Question 31

What are T killer cells?

Answer 31

Attack and kill host-body cells that display the foreign antigen, by releasing perforin

Question 32

What are T memory cells?

Answer 32

Provide long-term immunity, and remain in lymph nodes to respond rapidly if the same type of pathogen invades again

Question 33

What are T regulator cells?

Answer 33

Shut down the immune response once the pathogen has been removed

Question 34

WHta do lymphocytes respond to?

Answer 34

- An organisms own cells that have been infected by non-self material from a different species - Other cells of the same species as they are genetically different and therefore display different antigens - Cancer cells or transplanted cells as they display different antigens

Question 35

When will T lymphocytes respond to antigens?

Answer 35

Only respond to antigens that are presented on a body cell rather than to antigens within the body fluids. They also respond to a single antigen, therefore there are a vast number of T cells which each respond to a different antigen

Question 36

What are T lymphocytes covered with?

Answer 36

Receptors, which bind to antigens

Question 37

Why does immunity not last forever?

Answer 37

B and T lymphocytes have a limited lifespan. If you are not continuously exposed to an antigen then you will no longer be immune

Question 38

Why is the primary response slower than the secondary response?

Answer 38

There aren't many T lymphocytes that can bind to the pathogens antigens and not many B lymphocytes that can make the correct antibodies. Secondary response is faster as there are memory B and T lymphocytes that recognise the antigen and produce antibodies.

Question 39

Give 3 differences between primary and secondary response

Answer 39

Primary = pathogen enters for the first time Secondary = pathogen enters for second time Primary = B and T lymphocytes activated Secondary = B and T memory cells activated Primary = symptoms Secondary = no symptoms