Chapter 7: Immunity

Question 1

What is a pathogen?

Answer 1

A disease causing organism

Question 2

What are 6 types of transmission of pathogens/viruses?

ACID VB

Answer 2

Contact, body fluids, droplets, ingestion, airborne, vectors

Question 3

What is the difference specific and non-specific defences?

Answer 3

Non-specific defences work against all pathogens whilst specific defences target particular pathogens

Question 4

What is the body’s first line of defence?

Answer 4

Non-specific defence mechanisms like your intact skin and mucous membranes and their secretions

Question 5

What is the body’s second line of defence?

Answer 5

Non-specific defence mechanisms like phagocytic white blood cells, inflammation and fever and antimicrobial substances

Question 6

What is the body’s third line of defence?

Answer 6

Antibodies and specialised lymphocytes called B and T cells

Question 7

Name 4 protective reflexes

Answer 7

Coughing, sneezing, vomiting, diarrhoea

Question 8

Describe the non-specific internal defence of phagocytosis

Answer 8

Process by which phagocytes engulf and destroy microorganisms as well as cell debris. Includes macrophages, which are large phagocytic cells that were originally leucocytes that either engulf or destroy or release killer substances.

Question 9

Describe inflammation

Answer 9

A non-specific defence that causes swelling, redness and heat as a result of damage to the body’s tissue.

Question 10

Steps of inflammation

Answer 10

1. Mast cells stimulate and coordinate inflammation by releasing chemicals called histamine and heparin, resulting in swelling and redness in the damaged area.
2. Phagocytes are attracted by chemicals released by mast cells. Macrophages and leucocytes eat microorganisms and debris is consumes by phagocytosis.
3. Changed conditions in area of inflammation stimulates pain receptors so pain is felt.
4. Phagocytes filled with the bacteria die and form pus
5. Damaged tissues repaired by mitosis

Question 11

Describe functions of histamine

Answer 11

Released during inflammation by mast cells. Increases blood flow to the area by vasodilation, and make walls of blood capillaries more permeable resulting in heat, swelling and redness

Question 12

Describe functions of heparin

Answer 12

Release of heparin from mast cells prevents clotting in the immediate area of injury. Clot of fluid forms around damaged area and slows spread of pathogen

Question 13

Describe characteristics of a fever

Answer 13

Person feels cold, vasoconstriction in skin and shivering, increased heat production then pushes the temperature up rapidly, then the person feels hot and vasodilation and profuse sweating occurs

Question 14

Stages of a fever

Answer 14

Stages of fever

1. Pathogen presence detected by leucocytes
2. White blood cells accumulate and release pyrogens
3. Pyrogens detected by hypothalamus
4. Hypothalamus increases body temperature
5. Feedback - mechanisms to increase temp e.g. shivering

Question 15

What does a fever cause?

Answer 15

Causes:
Inhibits growth of pathogens
Denature proteins and enzymes for pathogen function
Metabolism of body occurs faster → increased repair

Question 16

Describe lymphatic system

Answer 16

Non-specific defence
Function to collect fluids escaping from blood capillaries
Network of lymph capillaries joined to lymph vessels,
Lymph nodes located along length of lymph vessels

Question 17

What do lymph nodes do?

Answer 17

Lymph nodes:
Lymph has cell debris, foreign particles and microorganisms
Nodes have lymph tissue and networks of fibres
Bacteria get trapped in network
Macrophages destroy particles
Lymph nodes can become swollen and sore

Question 18

What are two immune responses to deal with foreign invaders?

Answer 18

Humoral response/antibody mediated immunity: production of antibodies by B cells

Cell mediated immunity: formation of special lymphocytes by T cells

Question 19

Characteristics of B and T cells

Answer 19

Most lymph tissue made of B and T cells
B and T cells both produced in bone marrow
Half of cells produced in bone marrow move to thymus gland and mature into T cells
Other half stay in bone marrow to mature into B cells

Question 20

What are antigens

Answer 20

Antigen = any substance capable of producing an immune response
If an antigen gets into the body, body will produce antibodies

Question 21

Difference between non-self and self antigens

Answer 21

Large molecules produced by person’s own body do not cause immune response
= self antigen

Foreign compounds causing an immune response
= non-self antigen

Question 22

5 classes of anti bodies

Answer 22

IgG - resistance against many viruses, bacteria and bacterial toxins

IgE - accelerates local inflammation

IgD - found on surface of B cells

IgM - first type secreted after antigen arrives

IgA - primarily found in glandular secretions

Question 23

Describe the antibody antigen complex

Answer 23

• Antibody combines with antigen to form antibody antigen complex
• Active site of antigen combines with active site of antibody
• Antibody + antigen fit together like a lock and key
• Each antibody can only combine with a particular antigen - specific

Question 24

Describe antibody mediated (humoral) immunity

Answer 24

1. Humoral response begins when a foreign protein (antigen) binds to a specific B cell
2. Antigen binding stimulates B cells to proliferate, forming many plasma cells
   - Plasma cells make antibodies to attack and destroy a specific identified pathogen
3. Some B cells differentiate into long lived memory cells
   - These memory cells will rapidly produce antibodies if the same pathogen enters the body again

Question 25

What is the antibody mediated immunity primary and secondary response?

Answer 25

1st exposure to antigen - IgM is the first antibody secreted after antigen arrival

2nd exposure - IgG is secreted

Question 26

How do antibodies work

Answer 26

1. Combines with foreign body and inactivate them by inhibiting reactions
2. Bind to surface of viruses to prevent them from entering cells
3. Coat bacteria so they can be consumed by phagocytosis by macrophages
4. Causes foreign particles to clump together = agglutination
5. Dissolve the organism
   Makes soluble substances insoluble to undergo phagocytosis

Question 27

Describe cell mediated immunity

Answer 27

Is the intracellular phase of a viral and bacterial infections (e.g. cancer).
Thousands of T cells respond to a particular antigen. T cells become sensitised and enlarge to form clones of T cells and some will stay in lymphoid tissue as memory cells.

Question 28

3 types of T-cells

Answer 28

1. Killer T cells
2. Helper T cells
3. Suppressor T cells