Humoral and Cell mediated responses

Question 1

What is the immune response?

Answer 1

It is a homeostatic mechanism.

Question 2

What are the 2 responses of the immune response/system?

Answer 2

1. Humoral response/antibody-mediated immunity
2. Cell-mediated response

Question 3

What does the Humoral response/antibody-mediated immunty produce

Answer 3

B cells/B lymphocytes

Question 4

What does the cell-mediated response produce?

Answer 4

T cells/T lymphocytes

Question 5

Where are lymphocytes produced?

Answer 5

Lymphocytes a reproduced in the bone marrow. Some mature in the bone marrow and are called B cells. T cells mature in the thymus.

Question 6

Where are lymphocytes stored?

Answer 6

Lymphoid tissue

Question 7

Define what an antigen is

Answer 7

An antigen is a substance capable of causing an immune response.

Question 8

What are 3 examples of an antigen?

Answer 8

1. Virus particles
2. Toxins
3. Pollen

Question 9

What are self-antigens?

Answer 9

Self-antigens bind to self receptors on the T cell, causing the T cell not to destroy it as it recognises it as a part of the body.

Question 10

What are non-self antigens?

Answer 10

Non-self antigens bind to non-self receptors on T cells and are destroyed by them.

Question 11

Define what an antibody is

Answer 11

Antibodies are Y-shaped proteins that belong to a group of proteins called immunoglobulins. They contain active sites that have a specific shape and combine with a complimentary antigen.

Question 12

What are the 5 types of antibodies?

Answer 12

1. Immunoglobins A
2. Immunoglobins D
3. Immunoglobins E
4. Immunoglobins B
5. Immunoglobins M

Question 13

What are antigen-presenting cells (APC’s)?

Answer 13

APCs are immune cells that detect, engulf and inform the immune response about an infection.

Question 14

What are 3 examples of APCs?

Answer 14

1. Dendritic cells
2. Macrophages
3. B cells

Question 15

What is the molecule that attaches to the APC?

Answer 15

Major Histocompatibility Complex Class II (MHC II)

Question 16

What is Major histocompatibility complex class II?

Answer 16

MHC is a molecule that bonds to the antigen and displays it on the surface of the cell.

Question 17

What is antibody-mediated immunity?

Answer 17

Provides resistance to pathogens and toxins before they enter the cell.

Question 18

Outline the steps of antibody-mediated immunity

Answer 18

1. APC presents the antigen to a specific B-cell and T-cell helper cells
2. The APC and T helper cells release cytokines which activate more B cells
3. Activated B cells undergo mitosis.
4. Most B cells become plasma cells and secrete antibodies to circulate in the blood, lymph and extracellular fluid.
5. Antibodies combine with specific antigens to form an antigen-antibody complex and destroy inactive non-self antigens.
6. The remaining clones become memory cells which circulate all tissues in case of reinfection.

Question 19

How do antibodies work?

Answer 19

1. Inacatviate foreign enzymes or toxins by inhibiting their reaction with other cells
2. Bind to the surface of viruses and prevent them from entering
3. Coat bacteria with a substance so that phagocytes more easily consume them
4. Cause particles to undergo agglutination assisting phagocytes in consuming them
5. dissolve organisms
6. React with soluble substances to make them insoluble and more easily consumed by phagocytes

Question 20

What are memory cells?

Answer 20

A type of cell that recognises antigens to which the body has previously been exposed.

Question 21

Describe memory cell’s primary and secondary immune responses

Answer 21

The primary response is slower as the body must undergo the process of antibody mediated immunity. The secondary response is much faster due to memory cells recognising the antigen more quickly.

Question 22

What is cell-mediated immunity?

Answer 22

Provides immunity after the pathogen has entered the cell.

Question 23

Outline the steps of cell-mediated immunity

Answer 23

1. Pathogen is engulfed by macrophages and lysozymes destroy it and the APC presents the antigen on the surface
2. Help T cells only recognise antigens bound to MHC II
3. CYtokines are released by macrophages and helper T cells
4. Cytokines stimulate T cells to form clones. They are sensitised, enlarged and divide.
5. Most T cells become killer T cells or helper T cells and migrate to the place where large numbers of antigens are resent. Some become memory cells
6. Cytokines attract macrophages
7. Killer T cells release cytokines that cause the death of infected cells

Question 24

What do killer T cells do?

Answer 24

Killer T cells attach to antigens and destroy them.

Question 25

What are 3 things helper T cells do?

Answer 25

1. Secrete a substance that sensitises more lymphocytes
2. Secrete a substance that attracts more macrophages
3. Secrete a substance that enhances macrophage activity

Question 26

What are suppressor T cells?

Answer 26

Suppressor T cells act to slow down the immune response when the pathogen has been dealt with or the reaction is excessive. They are derived from killer T cells and secrete cytokines to signal lymphocytes to reduce activity.

Question 27

What are plasma cells?

Answer 27

A cell that develops from a B cell and produces antibodies.