immunity

Question 1

what does the immune system have cellls to detect?

Answer 1

pathogens
harmful foreign substances

Question 2

what are self and non self cells?
give examples of non self cells

Answer 2

self cells- the body’s own cells
non self cells-
cells from other organisms of the same species e.g. from a transplant
abnormall cells e.g. cancer cells
toxins
pathogens e.g. bacteria/fungi/HIV

Question 3

what are antigens?

Answer 3

moleculels thtaat generate an immune respoonse from lymphocytes when detected in the body

Question 4

antigen variability

Answer 4

pathogens DNA muutates frequently
if a mutation occurs in the gene coding for the antigen, the shape of the antigen chaanges
this means all previous immunity eeither natural through infection or artifical through vaccination is no longer effective as they have a memory of the antigen’s old shape

this is why a new flu vaccine has to be created each year as the pathogen mutates so rapidly so antigens change shape

Question 5

what happens if the pathogen gets past the first line of defence?
what is the first line of defence?

Answer 5

first line of defence- chemical and physical barriers e.g. stomach acid
white blood cells are the second line of defence
phagocytosis- non specific
lymphocytes- specific

Question 6

phagocytosis

Answer 6

phagocyte is attracted to pathogeen due to chemicals/debris or abnormal cell
phagocyte engulfs pathogen to form vesicle/phagosome
lysosomes fuse with vesicle
lysosomes/lytic enzymes released which hydrolyse pathogen

Question 7

what are antigen presenting cells?

Answer 7

any cell which does not have self cell antigens on its cell surface membrane

infected cells present viral antigens on cell surface membrane
cancer cells have abnormal shaped self cell antigens
macrophages/phagocytes which engulfed a pathogenn present viral antigens on cell surface membrane
cells off transpplated organ have differernt shaaped self cell antigens

Question 8

cell mediated response

Answer 8

helper T cell receptors collide with APC
activates helper t cells
undergo clonal selection/divide rapidly by mitosis to form large number of clones
some remain as helper t cells to stimulate b cells in humoura respsones
form memory cells for that shaped antigen
stimulate macrophages to carry out more phagocytosis
some form cytotoxic t cells

Question 9

Cytotoxic t cells

Answer 9

destroy infected or abnormal cells
produce a protein called perforin which emeds itseelf in the cell membrane
creates a pore/hole so substanes can leave/enter the cell.

common with viruses as they infect body cells
body cells are sacrificed to prevent further viral replication
this is why you have a sore throat when you have a cold as cytotoxic t cells build up in your throat to destroy the infected cells

Question 10

humoural response involving B cell

Answer 10

B cell antibodies collide with complimentary antigens
antigens engulfed by endocytosis and presented on cell surface membrane
when B cell antibodies collide with helper T cell receptors, this activates the b cell
b cell undergoes clonal selection
plasma cells and b memory cells produced
plasma cells secrete antibodies
b memory cells stay in blood for decades and can divdie rapidly if they come into contact with previously encountered antigen
large quantity of antigens produced rapidly so can desroy pathogen before it has any effect.

Question 11

antibodies

Answer 11

quartnary structure proteind
4 polypeptide chains
2 heavy chains
2 light chains

variable region- antibody binding site
constant region-the rest of the molecule

Question 12

agglutination

Answer 12

antibodies are flexible
they can bindn to multiple antigens and clump them together which makes it easier for phagocytes to locate and engulf pathogens in the body

Question 13

passive immunity

Answer 13

antibodies are introduced into body from outside soure
never exposed to pathogen so plasma cells and b memory cells not made
no long term immunity
e.g. passed from mother to baby via placenta or breast milk

Question 14

active immunity

Answer 14

immunity creaeted by your own immune system after being subjected to pathogen or its antigens
long term immunity

can be natural or artificial

natural- plasma cells and b memory cells produced after being infected with the pathogen
artificial- weak/inactive form of pathogen or its antigens introduced into body through vacciine

Question 15

vaccines

Answer 15

weak/inactive form of the pathogen or its antigens introduced into body via mouth or by injection
B cell antibodies collide with complimentary antigen
activates b cell
undergoges clonal selection/divides by mitosis
plasma cells produced whwichh secrete antibodies
b memory cells produced

Question 16

herd immunity

Answer 16

when most of the population are immune to a disease, this reduces the spread of the pathogen amongst the population.
as non vaccinated individuals less likely to come into contact with sosmeone who is infected
those not vaccinated
too young
already have lowered immunity
too ill

Question 17

HIV structure

Answer 17

capsid- outer protein coat
lipid envelope- made from membrane of helper T cell’s membrane
attachment proteeins- enable HIV to attach to CD4 protein of helper T cells
RNA and reverse transcriptase enzyme- genetic material.

Question 18

How HIV iis replicated

Answer 18

circulates around i n blood until attachment proteins attach to CD4 protein on helper t cell
HIV protein capsule fuses with helper T cell membrane
RNA and reverse transcriptase enzyme enter cell
reverse transcriptase converts viral RNAi into DNA
which enters helper T cell nucleus-why it is called a retrovirus
new viral proteins produced
new viral particles produced
which are assembleed and released from the cell

Question 19

HIV positive
AIDS

Answer 19

HIV positive is when a pereson has HIV
AIDS is when viral replication using helper t cells is interfering with normal functioning of immune system
helper T celels cannot produce adequate response to pathogens
person is vlunerrable to infections and cancer

destruction of immune systetm rather than HIV directly which leads to death

Question 20

antibody

Answer 20

single type of antibody which can be isolated and cloned
same tertiary strructure

Question 21

monoclonal antibody

Answer 21

specific tertiary structure
complimentary in shape to a speific antigen
produced by plasma cells

Question 22

what can monoclonal antibodies be used for?

Answer 22

medical diagnosis
medical treatment
pregnancy tests

Question 23

direct monoclonal antibody therapy

Answer 23

monoclonal antibodies are designed with tertiary structure complimentary to cancer cells
specific so do not harm other cells

bind to cancer cells
prevent chemicals from binding and causing uncontrollable cell division.

Question 24

indirect MCAB therapy

Answer 24

monoclonal antibodies designed with tertiary structure complimentary to cancer cells
have drugs attached to them so deliver drugs directly to cancer cells and kill them
-referred to as bullet drugs.