Immune system UNIT 3 AOS 2

Question 1

what is active natural immunity? give an example.

Answer 1

occurs when you come across a pathogen. normally you get sick, memory is formed. e.g. chicken pox, you will make antibodies to it and not be affected in subsequent exposures

Question 2

what is active artificial immunity? give an example.

Answer 2

Occurs via vaccination. Memory forms with possibly no symptoms. e.g. live and weak form of the pathogen that can still reproduce but leads to mild or no disease symptoms - measles

Question 3

what is passive natural immunity? give an example.

Answer 3

antibodies received naturally. e.g. received from mother whilst being breast fed, fetus is given immunity

Question 4

what is passive artificial immunity? give an example.

Answer 4

antibodies received via injection. e.g. snake antivenom

Question 5

state two first lines of defense and briefly describe

Answer 5

1. gastric acids: gastric acids lower the pH in the stomach. Many pathogens are unable to complete cellular processes in pH so low and therefore die.
2. Cilia in trachea: cilia in the trachea help to force mucous up and out of the trachea, back into the external environment. Pathogens that have been trapped in this mucous are therefore pushed out.

Question 6

state two second lines of defense and briefly describe

Answer 6

1. Phagocytosis: Phagocytes are a specialised type of immune cell that can engulf pathogens by phagocytosis. Once engulfs powerful enzymes in the cytoplasm of the phagocyte break down the pathogens. Phagocytes detect antigens with specialised receptors.
2. Cytokines: A diverse group of glycol-protein signalling molecules that work locally (paracrine) and act as messengers in co-ordination of immune response

Question 7

describe humoral immunity

Answer 7

• involved B cells
• they have antibodies embedded in their cell membranes
• When these antibodies bind to specific antigens, the B cells clone themselves, eventually forming B plasma cells which secrete antibodies and B memory cells which facilitate future immune responses to that specific antigen.
• B cells will phagocyte the virus. It will digest it and then present a small portion of it on its MHC 2 receptors. This is then recognised by the T Helper cells. The T Helper cell then tells the B cell to clone

Question 8

describe cell-mediated immunity

Answer 8

• Involved immune cells called T cells. T cells recognised antigen fragments presented by macrophages in an MHC antigen complex

Question 9

what do t helper cells do?

Answer 9

• T helper cells release interleukins that initiated the action of T cytotoxic cells which attack antigen directly. T helper cells also help to signal to B cells to clone, they also make cytokines to activate all the phagocytic cells
• T helper cells needs antigen presenting cells so that dendritic, macrophages and B cells can present the antigen to them
• The macrophage or dendritic cells phagocytes the antigen which is usually on the surface of a pathogen. They chop is up and re-present a small protein portion on their MHC 2 markers. T helper cell binds to MHC 2, this stimulates cloning into memory and effector cells.

Question 10

what do cytotoxic t cells do?

Answer 10

attack antigen directly

Question 11

what are antibodies?

Answer 11

• Antibodies are a group of specialist proteins that are essential to humoral immune responses
• Antibodies trap invading viruses or bacteria in large clumps. This makes it easy for macrophages to eat them.

Question 12

where are MHC I markers located?

Answer 12

located on the surface of all human cells with a nucleus (not red blood cells)

Question 13

where are MHC II markers located?

Answer 13

located on antigen-presenting white blood cells (B and T lymphocytes as well as macrophages)

Question 14

define pathogen?

Answer 14

a disease causing agent

Question 15

define antigen?

Answer 15

a foreign molecule that is recognised by lymphocytes and produces an immune response

Question 16

define disease?

Answer 16

a condition where the normal function of the body are disrupted

Question 17

define leukocyte

Answer 17

another name for white blood cells q

Question 18

define lymphocyte

Answer 18

type of white blood cells

Question 19

what happens in the primary exposure to a pathogen?

Answer 19

B and T cells take a while to produce active clones. Person often gets sick

Question 20

what happens in the secondary exposure to a pathogen?

Answer 20

B cells react quickly then they did in the primary exposure due to the presence of memory cells. Antibodies are produced a lot more rapidly. Person often does not get sick

Question 21

define infectious disease?

Answer 21

caused by a transmissible agent from one organism to another e.g. the common cold

Question 22

define non-infectious disease?

Answer 22

caused by anything else, can’t be transmitted e.g. cancer

Question 23

recognising self and non self?

Answer 23

Self antigens are displayed by every cell in your body that contains a nucleus, that carry MHC 1 markers. They display a small amino acid sequence and your B and T cells see it as ‘self and don’t attack
Non-self antigens are displayed on the MHC 2 markers of B cells, macrophages and dentritic cells, these are recognised as non-self antigens and your body will launch an attack against them