Immunity

Question 1

3 physical defences to infection:

Answer 1

.Skin (protein keratin)
.Trachea and Bronchi (mucus production)
.Stomach and gut (HCl acid)

Question 2

2 types of phagocytes and their roles:

Answer 2

-Neutrophils : Smaller and involved initiating immediate response
-Macrophages : Bigger and involved in specific immune response

Question 3

2 types of lymphocytes and what form can they be in:

Answer 3

-T lymphocytes, could be helper, cytotoxic, killer or memory cells
-B lymphocytes, could be memory or plasma cells

Question 4

Two specific responses to pathogens:

Answer 4

.Cellular (cell mediated) - highly specialised cells that target pathogens inside cells, T cells, T helper cell recognizes antigen of virus presented by macrophage
These activate T killer cells which will destroy infected host cells.
Also activates B cells to be an antigen presenting cell (to self), B plasma cells that produce antibodies.

.Humoral (antibody mediated) - targets pathogens in body fluids with antibodies, B cells

Question 5

Body’s non specific responses to pathogens:

Answer 5

.Inflammation = Histamines released by mast cells that cause vasodilation, Increased permeability of capillaries that helps bring white blood cells to affected site, leave the blood and enter the tissue.
Cytokines released.

.Phagocytosis = Phagocyte engulfs pathogen, forms phagosome
Lysosome fuses with phagosome and Lysozyme enzymes break down pathogen

.Fever = Inhibits replication of virus

Question 6

What is antigen presenting cell?

Answer 6

When white blood cell engulfs pathogen and present antigens on the surface

Question 7

What are interleukins?

Answer 7

T helper cells produce these in cell mediated and humoral response to stimulate more T cells as well as B cells to be produced.

Cell mediated = stimulates production of both
Humoral = stimulates production of B cells

Question 8

In humoral immunity what cell engulfs pathogen?

Answer 8

B cells

Question 9

What binds to antigen of B cell to produce interleukins?

Answer 9

T helper cells

Question 10

What do immunosuppressant drugs do?

Answer 10

Prevent immune system from attacking ‘self’ antigens, prevents organ and stem cell transplant rejection.

Question 11

Pathogens are coated in opsonins, what is their role?

Answer 11

Help phagocyte bind to pathogen in phagocytosis

Question 12

How does HIV virus create infection at T Helper cell?

Answer 12

1)Attach to CD4 receptor on host cell membrane
2)Viral RNA and reverse transcriptase released inside and used as template to produce complementary strand of DNA
3)Uses host cell’s enzymes to produce more viral components

Question 13

How does HIV develop into AIDS?

Answer 13

HIV particles replicate inside T helper cells,
killing or damaging them.
AIDS develops when T helper cell levels are low.
Individual unable to kill other pathogens.

Question 14

How can mutations in HIV affect body’s specific immune response?

Answer 14

1)Mutation will happen that will change antigen (glycoprotein) in
surface of virus
2)Memory cells won’t recognize new antigen
3)Secondary immune response not possible so another primary response needed, to present new antigens

Question 15

What engulfs TB bacteria when it’s inhaled?

Answer 15

Macrophage

Question 16

Stages of TB?

Answer 16

1)Primary Infection
2)Latent TB infection
3)Active TB infection

Question 17

What happens in primary infection?

Answer 17

Bacteria may be able to survive and reproduce in the macrophage, healthy people won’t develop TB at this stage

Question 18

How do bacteria then become dormant?

Answer 18

When the infected macrophage becomes encased in structures called tubercles

Question 19

What do the TB bacteria do to damage lung tissue?

Answer 19

Prevents lysosome from forming in the macrophage, so multiplies rapidly

Question 20

2 ways that HIV evades the immune system:

Answer 20

-Frequent mutations
-Invade host cells so antigens can’t be detected

Question 21

2 adaptations of gut to prevent pathogens entering body:

Answer 21

1)Acidic conditions which denature enzymes of microorganisms
2)Gut flora (bacteria) will outcompete other microorganisms, inhibiting growth and reproduction of pathogens

Question 22

Define conjugation:

Answer 22

Exchange of plasmids that allow mutations to pass between bacteria

Question 23

How do hospitals minimise spread of antibiotic resistant bacteria?

Answer 23

• Quarantine of affected patients
  -Antibiotics only prescribed if necessary, course completed to ensure no bacteria left behind to mutate
  -Hygiene code of practice including antibacterial gels

Question 24

Different names given to interleukins:

Answer 24

Cytokine, lymphokine, monokine, chemokine

Question 25

What is a reverse transcriptase in HIV?

Answer 25

Enzyme used to produce DNA from viral RNA

Question 26

How can interferon help against viruses?

Answer 26

Cells infected by virus produce interferons, these prevent viruses attaching to uninfected cells
Also reduces replication of viruses by inhibiting production of viral proteins