Specific immune system

Question 1

What is antibodies?

Answer 1

• They are Y-shapegly coproteins called immunoglobulins
• A protein consisting of 4 polypeptide chain
• they bind to a specific antigen on the pathgen or toxin that has triggered the immune response

Question 2

Describe the structure of antibodies

Answer 2

• Antigen-binding sites: complementary to a particular antigen on the pathogen
• Two light chain
• Two heavy chain
• Variable region: different on different antibodies due to different sequence of amino acid
• Constant region: same in all antibodies
• Disulfide bridges: strong bonds holding the antibodies in shape
• Hinge region: provide flexibility, allowing it to bind two seperate antigens, one at each of its antigen-binding sites

Question 3

How antibodies defend the body

Answer 3

• The antibody of the antigen-antibody complex acts as an opsonin so the complex is easily engulfed and digested by phagocytes
• Agglutination: Pathogens carrying antigen-antibody complexs to clump together so phagocytes can engulf a number of pathogens at the same time
• Anti-toxins: They bind to toxins produced by pathogens and neutralise the toxin
• Most pathogens can no longer bind to the host cell as the antigens are blocked by the antibodies

Question 4

What are the two types of lymphocytes in human body?

Answer 4

B lymphocytes (bone marrow)
T lymphocytes (thymus gland)

Question 5

What is opsonin

Answer 5

• proteins that attach to the outside of cells or pathogens to tell phagocytes to swallow and destroy them.
• Acts as ‘tags’ on pathogens

Question 6

What are the 4 T lymphocytes

Answer 6

T helper
T killer
T memory
T suppressor/ regulator

Question 7

What does T killer do

Answer 7

• They destroy the pathogens by producing perforin
• This kills the pathogen by making holes in the cell membrance so it is freely permeable

Question 8

What does T helper do

Answer 8

• They produce interleukins, which are a type of cytokine
• They stimulates B lymphocytes, which increases antibodies production
• They stimulates production of other types of T lymphocytes and attracts and stimulates macrophage to ingest pathogens with antigen-antibodies complex

Question 9

What does T memory do

Answer 9

• Produce immunological memory
• If they meet an antigen a second time, they divide rapidly to form a huge number of clones of T killer that destroy the pathogen

Question 10

What does T suppressor/ regulator do

Answer 10

They suppress immune system once the pathogen is eliminated
They ensure the body regconises self antigens and does not set up an autoimmune response
Interleukins are important in this control

Question 11

What is cytokine

Answer 11

• Cell-signalling molecules produced by mast cells in damaged tissue.
• They attract white blood cells to the site of damage

Question 12

What are the three types of B lymphocytes?

Answer 12

Plasma cell
B effector
B memory

Question 13

What does plasma cell do?

Answer 13

They produce antibodies to a particular antigen and release them into the circulation

Question 14

What does B effector do

Answer 14

They divide to form the plasma cell clones

Question 15

What does B memory do

Answer 15

• Provide immunological memory
• remember a specific antigen and enable the body to make a very rapid response when a pathogen carrying that antigen is encountered again

Question 16

What is cell-mediated immunity?

Answer 16

• T lymphocytes respond to the cells of an organism that have been changed in some way
• E.g. by a virus infection
• This is particularly important against virus and early cancers.

Question 17

What is the processes of cell-mediated immunity?

Answer 17

1. • Macrophages engulf and digest pathogens in phagocytosis.
   • They process the antigens from the suface of the pathogen to form antigen-presenting cells (APCs)
2. • The receptors on some of the T helper cells fit the antigens.
   • These T helper cells become activated and produce interleukins, which stimulates more T lymphocytes to divide rapidly by mitosis.
   • They form clones of identical activated T helper cells that all carry the right antigen to binds to a particular pathgen
3. • The cloned T lymphocytes may:
   • develop into T memory cells, which gives a rapid response if this pathogen invades the body again
   • Produce interleukins that stimulate phagocytosis
   • Produce interleukins that stimulate B lymphocytes to divide
   • Stimulate the developmetn of a clone of T killer that are specific for the presented antigen and then destroy infected cells

Question 18

What is humoral immunity?

Answer 18

The body response to antigens found outside the cells, then produces antibodies that are soluble in the blood and tissue fluid and are not attached to cells

Question 19

What is the process of humoral immunity?

Answer 19

1. Activated T helper bind to the B cell APC.
   This is clonal selection - the point at which the B cell with the correct antibody to overcome a particular antigen is selected for cloning
2. Interleukins produced by the activated T helper activate the B cells
3. The activated B cell divides by mitosis to give clones of plasma cells and B memory cells. This is clonal expansion
4. Cloned plasma cells produce complementary antibodies to the antigen, act as opsonins or agglutination. This is primary immune response
5. Some cloned B cells develop into B memory. The B memory cells divide rapidly to form plasma cell clones. This is the secondary immune response

Question 20

What is autoimmune disease?

Answer 20

When the immune system stops regconising ‘self’ cells and starts to attack healthy body tissue

Question 21

What are three types of autoimmune disease?

Answer 21

• Type 1 diabetes
• Rheumatoid arthritis
• Lupus

Question 22

What body part is affected by type 1 diabetes?

Answer 22

The insulin-secreting cells of the pancreas

Question 23

What body part is affected by rheumatoid arthritis?

Answer 23

Joints - especially in the hands, wrists, ankles and feet

Question 24

What body part is affected by Lupus?

Answer 24

• Often affects skin and joints and causes fatigue
• can attack any organ in the body including kidneys, liver, lungs or brain

Question 25

What are the treatment for Type 1 diabetes?

Answer 25

* Insulin injections * Pancreas transplant * Immunosuppressant drugs

Question 26

What are the treatment for rheumatoid arthritis?

Answer 26

* No cure * anti-inflammatory drugs * steriods * immunosuppressants * pain relief

Question 27

What are the treatment for Lupus?

Answer 27

* No cure * Anti-inflammatory drugs * steriods * immunosuppressants * various others