Cell recognition and the immune system

Question 1

What is immunity?

Answer 1

When the bodies defenses are better prepared for an second infection from the same pathogen and can kill i before it causes any harm.

Question 2

How do lymphocytes come to recognise body cells in the fetus?

Answer 2

By colliding with the body cells found in the fetus, cells in the fetus are exclusively body cells are it is protected from the external environment. Those lymphocytes which fit body cells will undergo apoptosis.

Question 3

In what form is the bodies first line of defense against pathogens?

Answer 3

Physical or chemical

Question 4

Name two types of white blood cell.

Answer 4

Phagocyte

Lymphocyte.

Question 5

Describe the 6 stages in phagocytosis

Answer 5

• Phagocyte is attracted towards cell by chemical attractants,
• Attach to cell by receptors on cell surface membrane,
• Engulf cell to form a phagosome,
• Lysosomes fuse to phagosome,
• Lysozyme hydrolyses cell wall,
• Soluble products are absorbed into cytoplasm of phagocyte.

Question 6

What is an antigen?

Answer 6

Any part of a cell which identifies it as non-self by the body, induces an immune responce.

Question 7

Describe a B-cell

Answer 7

Mature in the bone-marrow, associated with humoral immunity.

Question 8

Describe a T-cell

Answer 8

Mature in thymus gland, associated with cell mediated immunity.

Question 9

What do T-cells respond to?

Answer 9

Antigen-presenting cells, cancer cells, implanted cells and body cells invaded by a virus.

Question 10

Describe cell-mediated responce.

Answer 10

Phagocyte presents the foreign antigens. Th cells bind to this stimulating the cell to divide rapidly into clones. These clones can:

• develop into memory cells,
• activate phagocytes and b-cells,
• activate Tc-cells.

Question 11

What protein do Tc-cells make?

Answer 11

Perforin

Question 12

How does the antigen enter the complementary B-cell.

Answer 12

Endocytosis

Question 13

What do plasma cells do?

Answer 13

Secrete antibodies into the blood stream.

Question 14

What are memory cells?

Answer 14

Remain in the body for a long time, are specific to a certain pathogen so can divide rapidly if activated by it.

Question 15

How are B-cells activated?

Answer 15

They take up antigens in the blood stream and preset them on its surface, when a complementary T-cell binds to the antigen it activates the B-cell causing it to divide.

Question 16

What is an antibody made up of?

Answer 16

Two heavy polypeptide chains, two light polypeptide chains and two binding sites.

Question 17

What is a monoclonal antibody?

Answer 17

An antibody which has been isolated and cloned for medical use. Made from the same parent cell.

Question 18

What is direct monoclonal antibody therapy?

Answer 18

Antibodies are produced that are specific to antibodies on cancer cells, these are given to the patient blocking the chemical signals which stimulate uncontrolled growth.

Question 19

What is indirect monoclonal antibody therapy?

Answer 19

A radioactive or cytotoxic drug is attached to the antibody, when it binds to the cancer cell it kills it.

Question 20

What is active immunity?

Answer 20

Direct contact with the antigen or its pathogen. Natural through direct contact with the pathogen through infection or artificial through vaccination.

Question 21

What is passive immunity?

Answer 21

Introduction of antibodies into the body from an external source.

Question 22

Name 5 features of a successful vaccination programme?

Answer 22

• Economically available in sufficient quantities,
• Few side effects,
• Means of transporting and storing,
• Means of administering population,
• Most of population must be immune: herd immunity.

Question 23

What is herd immunity?

Answer 23

When a sufficient percentage of the population is vaccinated to prevent the spread of the disease.

Question 24

Suggest three reasons vaccinating a population may fail to prevent the spread of disease.

Answer 24

• It may fail to induce immunity in some people,
• Individuals may be infected before vaccination has produced immunity,
• Antigentic variability due to mutations.

Question 25

What disease does the human immunodeficiency virus cause/?

Answer 25

Acquired immune deficiency syndrome.

Question 26

What is the enzyme found in HIV?

Answer 26

Reverse transcriptase - converts RNA into DNA to take over the cells function.

Question 27

What group of viruses does HIV belong to?

Answer 27

Retrovirus’

Question 28

What protein does HIV bind to on cells?

Answer 28

CD4

Question 29

Describe how the ELISA test works. (enzyme linked immunosorbant assay)

Answer 29

Apply the sample to a surface and then wash away and antigens which did not bind. Add the complementary antibody and allow to bind, add a second antibody complementary to the first with an enzyme attached. Add the colourless substrate of the enzyme which changes colour when reacted with the enzyme.