Defensive functions of mammalian blood

Question 1

Antigen meaning

Answer 1

Glycoprotein of cell membrane which stimulates an immune response

Question 2

B-lymphocytes

Answer 2

Mature in bone marrow. Involved in humoural immunity.

Question 3

T-Lymphocytes

Answer 3

Mature in thymus gland. Involved in cell-mediated immunity

Question 4

What is antigen variability?

Answer 4

When pathogens change surface antigens as a result of mutations in genes. Can’t be recognised by memory cells so body has to carry out primary immune response.

Question 5

Process of phagocytosis

Answer 5

1 - Phagocyte attracted to pathogen by its chemical products
2 - Phagocyte receptors attach to antigen
3 - Pathogen engulfed - phagosome forms
4 - Lysosomes fuse with phagosome and release lysozymes
5 - Lysozymes hydrolyse and destroy pathogen - the phagocyte presents antigens

Question 6

What is cell-mediated immunity?

Answer 6

1 - Phagocyte displays antigen on its cell membrane
2 - Receptors on specific T-cell fit exactly to these antigens
3 - Activates T-cell to divide by mitosis and form clones of identical cells
Either develop into…
- Memory cells, stimulate phagocytes, stimulate B-cells to divide or activate cytotoxic cells

Question 7

What is humoural immunity?

Answer 7

1 - B-cell attaches to antigen via antibody, antigen taken in, processed and presented on its cell membrane
2 - T-cell attaches to processed antigen and activates B-cell
3 - B-cell divides by mitosis to form either plasma or memory cells
Plasma cells produce antibodies

Question 8

What are antibodies’ structure?

Answer 8

2 light polypeptide chains and 2 heavy polypeptide chains held together by disulfide bridges. Have a variable region that determines what antigen it attaches to, to form an antigen-antibody complex

Question 9

What is agglutination?

Answer 9

Pathogens clumped together to make it easier for phagocytes to reach them

Question 10

What are vaccines?

Answer 10

Contain antigens that cause body to produce memory cells against them in case of reinfection

Question 11

What is herd immunity?

Answer 11

Vaccines protecting individuals that have them and reducing occurence of passing disease to unvaccinated people so less likely to catch disease

Question 12

Active Vs. Passive immunity

Answer 12

• Active requires exposure to antigen, passive doesn’t
• Active is slower than passive
• Passive involves antibody from outside source
• Active immunity provides long term protection while passive doesn’t
• Active involves antibodies, passive doesn’t