Third line of defence

Question 1

Specific defence

Answer 1

Directed towards a particular pathogen

Question 2

Immune response

Answer 2

homeostatic mechanism (maintenance of a constant internal environment), specific response

Question 3

Types of specific immunity

Answer 3

Humoral or antibody mediated (B cells- type of lymphocyte), Cell mediated (T cells- type of lymphocyte)

Question 4

Compare B and T cells

Answer 4

Both produced in the bone marrow, B cells mature in the bone, T cells mature in the thymus gland

Question 5

Antigen

Answer 5

Any substance capable of causing specific immune response E.g- proteins, carbohydrates, cell walls, pollen grain

Question 6

Why do people have different allergies

Answer 6

Everyone has different antigens

Question 7

Self-antigens

Answer 7

Materials recognised by the immune system as belonging to the organism, Don’t cause an immune response

Question 8

Non-self-antigens

Answer 8

Materials recognised by the immune system as not belonging to the organism (foreign), Stimulates an immune response (both specific and non-specific)

Question 9

Anti-bodies

Answer 9

Specialised protein produced in response to a non-self-antigen, Combine with the antigen for which they are specific, Protein group called immunoglobulins (Ig)

Question 10

What can anti-bodies do (5)

Answer 10

Combine with bacterial/viral toxins/enzymes and inhibit them, Bind to viruses to prevent cell entry, Coat bacteria (making it harder to move) for easier phagocytosis, Cause agglutination (clumping) of foreign particles, Make substances insoluble hence easier to phagocytose

Question 11

Antigen-antibody complex

Answer 11

Specific antibody (depicted as Y’s) attaches to a specific antigen, Should result in destruction/inactivation of the antigen

Question 12

What is the humoral response for

Answer 12

Extracellular bacteria and viruses

Question 13

Humoral response

Answer 13

Pathogen invades the body, Macrophage engulfs the pathogen and presents the antigen to a B cell OR B cells are stimulated by cytokines (released by mast cells) OR antigen activates the B cell, B cell enlarges and determines how to produce antibody, B cell divides into clones (which mostly become plasma cells- specific type of B cell), Plasma cell produce antibodies which travel in the blood stream and combine with specific antigens to destroy them, Some clones of B cells become memory cells that remain in the body to increase immune response when reinfection occurs and respond faster and in greater amounts to re-exposure to the antigen

Question 14

Primary response

Answer 14

First exposure to antigen- slower as the B cells have to differentiate and build antibody levels

Question 15

Secondary response

Answer 15

Re-exposure response- faster as the memory cells don’t need to differentiate again

Question 16

What is cell-mediated immunity for

Answer 16

Provides resistance to the intracellular (in the cells) phase of bacterial and viral infections, fungi and parasites

Question 17

What is cell-mediated immunity involved in

Answer 17

Organ rejection in transplants and fighting cancer cells

Question 18

Cell-mediated immunity

Answer 18

T cells stimulated by cytokines in humoral immunity or by intercellular infection of non-self-antigens, Foreign antigens sensitise T cells which then enlarge, divide and clone into memory cells or one of three types of T cells (Killer T cell, helper T cell, Suppressor T cell), Killer T cells target and destroy infected cells via phagocytosis, Macrophages activate helper T cells, Suppressor T cells release substances that inhibit B and T cell activity

Question 19

Helper T cells

Answer 19

Assist in both humoral and cell mediated immunity, Cause more B lymphocytes to become sensitised, attract macrophages and intensify phagocytosis of macrophages, Secrete cytokines that attract B and T cells to the area