Chapter 11 - Specific Resistance To Infection

Question 1

Describe what a lymphocyte is.

Answer 1

Cells involved in both non-specific defence. About 20-30% of white cells in the blood are lymphocytes. The combined weight of lymphocytes in a person’s body is over a kilogram.
Most lymphocytes are produced in the bone marrow or lymphoid tissues. They roam throughout the body, they can travel through tissue, blood, lymphs

Question 2

Describe what a macrophage is.

Answer 2

Macrophages are also involved in both non-specific and specific defence. They are large phagocytic cells that develop from a type of white blood cell. Macrophages are able to consume foreign substances and micro organisms by phagocytosis.

Question 3

What are specific defences?

Answer 3

Specific defences are those directed towards a particular pathogen. For example if you get infected (or vaccinated) with chicken pox virus, the body will make antibodies to combat the virus. Those antibodies are only effective against chicken pox virus and will not work against any other virus or bacterium.

Question 4

What is the immune response?

Answer 4

The immune response is a homeostatic mechanism. When micro-organisms or foreign substances enter the body, the immune response helps to deal with the invasion and restore the internal environment to it’s normal condition.

Question 5

What are the two parts of the immune response?

Answer 5

1. The humeral response (or antibody-mediated immunity) involves the production of special proteins called antibodies. Antibodies circulate the body and attack invading agents.
2. The cell mediated response involves the formation of special lymphocytes that destroy invading agents.

Question 6

Where can lymphoid tissue be found?

Answer 6

Mostly in the lymph nodes, but it also occurs in other parts of the body, such as the spleen, the thymus gland and the tonsils.

Question 7

What do B-cells and T-cells do?

Answer 7

B-cells provide antibody-mediated immunity
T-cells provide cell-mediated immunity

Much of the lymphoid tissue is composed of the two types of lymphocytes.

Question 8

Describe where and how T-cells and B-cells mature.

Answer 8

They are produced in bone marrow and both end up in the lymphoid tissue, but they mature by following two different routes between bone marrow and lymphoid tissue. About half the cells produced by the bone marrow go to the thymus, where they mature into T-cells before being incooperated into the lymphoid tissues. The other half the the cells mature in the bone marrow and become B-cells and then also become part of the lymphoid tissues.

Question 9

What is an antigen?

Answer 9

An antigen is any substance capable of causing a specific immune response. It causes the body to produce specific antibodies.
Antigens are large molecules and can be proteins, carbohydrates, lipids, or nucleic acids. Toxins produced by bacteria are also antigens. Blood cells of a foreign blood group, and such things as pollen, grains and egg white contain antigens.

Question 10

What are self antigens?

Answer 10

Large molecules produced in a person’s own body that do not cause an immune response.

Question 11

What are non-self antigens?

Answer 11

Foreign compounds that do trigger an immune response.

Question 12

What are antibodies?

Answer 12

An antibody is a specialised protein that is produced in response to a non-self antigen.
Antibodies belong to a group of proteins known as immunoglobulins, often represented as Ig.

Question 13

What are the 5 classes of antibodies?

Answer 13

They vary in structure.

IgA, IgD, IgE, IgG, IgM.

Question 14

What is an antigen -antibody complex?

Answer 14

The antibody produced in response to an antigen that combines with that antigen. This active site fits together like a lock and key model. Each antibody can combine with only one particular antigen.

Question 15

What is antibody -mediated immunity?

Answer 15

Provides resistance to viruses, bacteria and bacterial toxins before these micro-organisms or substances enter the body’s cells.

The humoral response involves the production and release of antibodies into the blood and the lymph.

Question 16

What is a clone?

Answer 16

When an antigen activates B-cells, they enlarge and divide into a group of cells. Most of the cells become plasma cells, which secrete the specific antibody capable of attaching to the active site of the antigen.

Question 17

What are memory cells?

Answer 17

The B-cells of the clone that did not differentiate into plasma cells remain as memory cells. These memory cells spread to all body tissues to allow the response to occur more rapidly should the antigen enter the body again.

Question 18

What are the primary and secondary responses?

Answer 18

Primary response - on the first exposure to an antigen the immune reaction is called the primary response. The immune system usually responds very slowly. The primary response leaves the immune system with a memory of that particular antigen.

Secondary response - the second or subsequent exposure to the same antigen, the response is much faster because of the activity of the memory cells.

Question 19

What can antibodies do?

Answer 19

• combine with foreign enzymes or bacterial toxins, or inactivate them by inhibiting reaction with other cells or compounds.
• bind to the surface of viruses and prevents the viruses from entering cells.
• coat bacteria so that the bacteria are more easily consumed by phagocytes.
• cause particles such as bacteria, viruses or foreign blood cells to clump together- a process known as agglutination.
• dissolve organisms
• react with soluble substances to make them insoluble and thus more easily consumed by phagocytes.

Question 20

What is cell-mediated immunity?

Answer 20

Cell-mediated immunity provides resistance to the intracellular phase of bacterial and viral infections. It is also important in providing resistance to fungi and parasites as well as being involved in the rejection of transplants of foreign tissue and cancer cells.

Question 21

What are the three different types of T-cells that do not become memory cells?

Answer 21

• Killer T-cells migrate to the site of infection and deal with the invading antigen. They attach to the invading cells and secrete a substance that will destroy the antigen.
• Helped T-cells play an important role in both humoral and cellular immunity.
• Suppressor T-cells act when the immune activity becomes excessive or the infection has been dealt with successfully. They slow down the immune response.

Question 22

What do the substances that helper T-cells release do?

Answer 22

• cause lymphocytes at the infection site to become sensitised, this intensifying the response.
• attract macrophages to the place of infection so that macrophages can destroy the antigens by phagocytosis.
• Intensifies the phagocytic activity of macrophages

Question 23

What is the difference between artificial immunity and natural immunity?

Answer 23

Natural immunity occurs without any human intervention where as artificial immunity results from giving people an antibody or antigen

Question 24

What is the difference between passive and active immunity?

Answer 24

Passive immunity is when a person is given antibodies produced by someone else.
Active immunity is when the body is exposed to a foreign antigen and manufactures antibodies in response to the antigen.

Question 25

What is Vaccination?

Answer 25

The artificial introduction of antigens of pathogenic organisms so the ability to produce the appropriate antibodies is acquired without the person having to suffer the disease.

Question 26

What are the 4 types of traditional vaccines?

Answer 26

• One type contains living attenuated micro-organisms of reduced virulence. (Micro-organisms with reduced ability to produce disease symptoms).
• a second type contains dead micro-organisms.
• a third type is made from filtrate of bacterial cultures containing toxins, which can be inactivated. When they are inactivated, they are called toxoids.
• a fourth type of vaccine is called a sub-unit vaccine, which is when a fragment of the organism is used to provoke immune response.

Question 27

What is herd immunity?

Answer 27

When majority of the population is immune to a virus that the few who are not immune have a lower risk of contracting that virus.

Question 28

What are antibodies?

Answer 28

Drugs that are used to fight micro-organisms, particularly bacteria.

Question 29

What are the two types of antibiotics?

Answer 29

Bactericidal antibiotics kill bacteria by the changing the structure of the cell wall or cell membrane, or by disrupting the action of essential enzymes.

Bacteriostatic antibodies stop bacteria from reproducing by disrupting protein synthesis.

Question 30

What is the difference between broad-spectrum antibiotics and narrow-spectrum antibiotics?

Answer 30

Broad-spectrum antibiotics affect a wide range of different types of bacteria.

Narrow-spectrum antibiotics affect only specific types of bacteria.

Question 31

What is multiple drug resistance?

Answer 31

When some bacteria are resistant to all available types of antibiotics.

Question 32

What are antiviral drugs?

Answer 32

Antiviral drugs are used specially for treating viral infections.