Antigens and Immune Response

Question 1

What are antigens?

Answer 1

Molecules that can generate an immune response when detected by the body

Question 2

Where are antigens found?

Answer 2

Surface of cells

Question 3

What are foreign antigens?

Answer 3

Antigens that aren’t normally found in the body that the immune response usually responds to

Question 4

What are pathogens?

Answer 4

Organisms that cause disease

Question 5

What triggers an immune response?

Answer 5

Abnormal or foreign antigens

Question 6

What are toxins?

Answer 6

Poisons that are molecules not cells

Question 7

Describe the process of phagocytosis:

Answer 7

1. Phagocyte recognises foreign antigens on pathogen.
2. Cytoplasm of phagocyte moves round pathogen, engulfs it
3. Pathogen now contained in phagocytic vacuole in cytoplasm of phagocyte.
4. Lysosome fuses with phagocytic vacuole. Lysozymes break down pathogen.
5. Phagocyte presents pathogen’s antigens. Acts as antigen presenting cell.

Question 8

How is a T-Cell activated?

Answer 8

The antigens on the pathogen bind to the receptor proteins on the T-Cell forming an antibody-antigen complex.

Question 9

What do helper T-cells do?

Answer 9

Release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells. Activate B-cells.

Question 10

What do cytotoxic T-cells do?

Answer 10

Kill abnormal and foreign cells

Question 11

What do B-cells do?

Answer 11

Secrete antibodies

Question 12

How is a B-cell activated?

Answer 12

Binding of an antigen to an antibody on the surface of a B-cell and substances released from helper T-cells.

Question 13

What is this process called?

Answer 13

Clonal selection

Question 14

What do activated B-cells divide into?

Answer 14

Plasma cells

Question 15

What do plasma cells do?

Answer 15

Secrete loads of antibodies specific to the antigen.

Question 16

What are monoclonal antibodies?

Answer 16

An antibody produced from a single group of genetically identical B-cells.

Question 17

What is agglutination?

Answer 17

When pathogens become clumped together because the antibody has 2 binding sites. Phagocytes bind to these antibodies and phagocytose many pathogens at once.

Question 18

What are antibodies?

Answer 18

Proteins

Question 19

What makes an antibody specific?

Answer 19

Variable regions which have unique tertiary structures complementary to one specific antigen.

Question 20

What is the cellular response?

Answer 20

T-cells and other immune system cells that they interact with, e.g. phagocytes, form the immune response.

Question 21

What is the humoral response?

Answer 21

B-cells, clonal selection and the production of monoclonal antibodies form the humoral response.

Question 22

What is the primary response?

Answer 22

When an antigen enters the body for the first time, it stimulates an immune response - the primary response. This is slow because there aren’t many B-cells to make the antibody needed for the antigen but will eventually overcome the infection. Person shows symptoms meanwhile. After being exposed T and B cells produce memory cells for the next infection.

Question 23

What is the secondary response?

Answer 23

If same pathogen enters again, body will respond quicker and stronger. Clonal selection happens faster. Memory B cells activated and can divide. Memory T cells activated to kill. Often don’t show symptoms.