cell recognition and the immune system

Question 1

non specific defenses against microorganisms

Answer 1

1) skin - acts as a barrier stops penetrating microorganisms
- sebum that is harmful to bacteria

2) trachea lined with mucous membranes that release mucous - trap microorganisms killed by fagocyte
- contains lysozymes

3) lysozymes in eyes

4) stomach has HCL - kills pathogens

5) mouth/nose - body expels pathogen EXPULSIVE REFLEXES - vomit, sneeze

6) cuts - blood clotting

Question 2

antigen

Answer 2

molecules present on the surface of cells, which trigger an immune response

Question 3

types of substances the immune system must identify

Answer 3

• pathogens
• cells from other organisms of the same species
• abnormal body cells
• toxins

Question 4

phagocytosis in macrophages

Answer 4

1) phagocytosis happens normally as it would with neutrophil

2) glycoproteins from cytoplasm bind to antigens, forming major histocompatibility - antigen complex (HMC)

3) HMC - antigen complex moves to cell surface of phagocyte

3) macrophage is a antigen presenting cell

elicits the specific immune system response

Question 5

phagocytosis in neutrophils

Answer 5

1) opsonin attract phagocytes. Phagocytes receptors bind to opsonin on pathogen antigen

2) phagocyte engulfs pathogen and forms a phagosome

3) lysosymes move to phagosome and fuse with it, forms a PHAGOLYSOSME

4) lysozymes hydrolyse pathogen + break it down

Question 6

the process of humoral immunity

Answer 6

firstly a T helper cell must become activated
1) phagocytosis by macrophage takes place. pathogen is hydrolysed + antigens are put out on the cell membrane

2) Macrophage becomes a APC, APC travels in blood until the antigen is met with a T helper cell with receptor COMPLIMENTARY to antigen on APC

3) t helper cell receptor binds to antigen on APC as tertiary structure is complimentary. once they bind, cytokines are released :
trigger mitosis activated T helper cells
stimulate macrophages to undergo phagocytosis

secondly the B lymphocyte must become activated

1) pathogen travels in the body until B lymphocytes receptors are specific to antigen

2) B lymphocytes and antigen bind together and it engulfs + digests pathogen = becomes a APC

3) activated T helper cell from before form earlier attaches to antigen APC and then cytokines release that activate the B cell
this causes
- B cells undergo mitosis of
- plasma cells (antibody production) MONOCLONAL ANTIBODIES
- B memory cells for later use if pathogen is encountered again

Question 7

the difference between primary and secondary immunity

Answer 7

primary immunity - the production of plasma cells with antibodies by the activation of B lymphocytes

Secondary immunity - B memory cells produced by previous interaction with a pathogen . these stay in the blood for a long time, so that if the same antigen comes the body can quickly replicate and stop symptoms from happening

Question 8

why is there a receptor that is complimentary to at least one antigen

Answer 8

there are billions of T cell / B cells with different receptor tertiary structure so that there has to be complimentary to a antigens active site

Question 9

cell mediated immunity - what type of cells are attacked by immune system

Answer 9

Lymphocytes respond to cells that have been infected by non self material
respond to;
- cells that have been infected by virus
- cells genetically different, from same species
- cancer cells - they produce

Question 10

constant and variable regions of a anttobdy

Answer 10

constant region - towards end of molecule, this is the same structure in every type of antigens

variable region - this has a different tertiary structure for every single antigen, one antibody can only bind to one antigen

Question 11

structure of an antibody

Answer 11

2 heavy long chain
2 short light chain these are held by disulphide bonds

2 variable regions where 2 antigens identical can fit

Question 12

functions of antigens

Answer 12

• acts as opsonin, tagging antigens for phagocytes to carry out phagocytosis
• agglutination (sticks pathogens together, prevents further invasion of host cells
• stick to toxins from bacteria to stop damaging of cells ( ANTI - TOXIN)

Question 13

natural active immunity

Answer 13

the body receives a pathogen naturally from environment. body fights it off and creates memory cells and antibodies
these memory cells stay in the bloodstream for a long time, providing immunity

Question 14

artificial active immunity

Answer 14

person does not get antigens naturally, but artificially from vaccines
weak / dead dose to elicit immune response. memory cells are created. stay long time in blood stream meaning that there is immunity

Question 15

natural passive immunity

Answer 15

body gains ANTIBODIES rather than ANTIGENS
antibodies are received from natural ways e.g babies in the placenta are given mothers antibodies + breast MILK containing antibodies

Question 16

artificial passive immunity

Answer 16

antibodies are received medically from doctors
e.g tetanus is injected into horses and the antibodies the horse made are extracted and injected into a human

not received naturally, so its passive

Question 16

what is a vaccine

Answer 16

weak/inactivated dose of pathogen. Immune system easily produces antibodies + memory cells

if person comes into contact with pathogen, secondary immune response is activated
pathogen is destroyed before any symptoms occur

ARTIFICAL ACTIVE IMMUNTIY

Question 16

herd immunity

Answer 16

herd immunity is major of the population is vaccinated, this protects those that are not vaccinated

unlikely to spread it to unvaccinated people

this is only available if a high percentage has been vaccinated otherwise it will break down

Question 17

how effective are vaccines?

Answer 17

• dependent on the disease, some diseases prone to mutations - ANTIGENIC VARIABILITY
  causes many strains and so different antigens cause the vaccine not to be effective as the antibodies created by immune system is not complimentary to antigens of diff strain