Cells-Immunity Flashcards
What is a pathogen?
a disease causing micro-organism
e.g. bacteria, virus, fungi
Body’s defence against pathogens?
Barriers (prevents pathogens entering the body)
Phagocytes (perform phagocytosis and stimulate specific response)
Specific Response/ cell mediat (uses lymphocytes to produce memory cells and antibodies)
What are the Barriers (I)?
Skin
Cilia & Mucus in Lungs
Stomach Acid
Lysozymes in tears
Describe the process of Phagocytosis ?
pathogen releases chemicals
this attracts the phagocyte
the phagocyte binds to the pathogen
the phagocyte engulfs the pathogen
forms a phagosome around the pathogen
lysosomes inside the phagocyte release digestive enzymes into the phagosome
breaking down the pathogen by hydrolysis
Describe the Specific Response (III)?
phagocytes perform phagocytosis (engulf and destroy pathogen) without destroying the antigen, they place antigens on their surface, they present antigens
t lymphocytes (t cells) bind to the antigen and become stimulated
they divide by mitosis to form 3 types of cells: t helper, t killer, t memory
t helper cells stimulate b lymphocytes (b cells)
t killer cells kill infected cells (infected by virus)
t memory cells provide long term immunity
b lymphocytes (b cells) engulf and present antigens on their surface, the t helper cells bind to this
the b cells become stimulated and divide by mitosis to make 2 types of cells: Plasma
Cells & B Memory Cells
Plasma cells make antibodies
B memory cells provide long term immunity
What is an antigen?
a protein on the surface of a pathogen that stimulates an immune response
How does the immune response lead to production of antibodies?
the phagocytes stimulate the t cells, the t cells form t helper cells, the t helper cells stimulate the b cells, the b cells form plasma cells, the plasma cells make antibodies
What is an antibody?
protein
made by plasma cells
has 3 regions: variable region, hinge region, constant region
variable region has a different shape in each antibody, contains the antigen binding sites, these bind to
complementary antigens (on a pathogen) to form an antigen-antibody complex, destroying the pathogen
hinge region gives the antibody flexibility
constant region the same shape in all antibodies, binds to phagocytes to help with phagocytosis
How do Memory cells (B/T) work?
made during the specific immune response after a new infection by a pathogen (called a primary infection)
B and T memory cells remain in the blood
if person is reinfected by the same pathogen (called a secondary infection) the memory cells will recognise
the pathogen and produce antibodies RAPIDLY and to a LARGE amount
therefore the pathogen is killed before it can cause harm = immunity
How does a vaccine produce immunity?
involves giving an injection that contains dead/weakened pathogens that
carry antigens which stimulates the immune response leading to production of antibodies & memory cells
Active immunity
individual has memory cells – can make their own antibodies & provides long term immunity
Passive immunity?
person given antibodies, these work then die, no long term immunity, no memory cells.
How does active immunity occur?
naturally = by primary infection, artificially = by vaccination
How does passive immunity occur?
naturally = from mother to baby (placenta or breast milk), artificially = by injection
Successful Vaccination Programme?
produce suitable vaccine (effective – make memory cells, does not cause disease, no major side effects,low cost,easily produced/transported/stored/administered)
herd immunity
What is herd immunity?
when a large proportion of the population is vaccinated, therefore most people will be
immune, only a few will not be a immune, increases chance of non-immune person coming into contact with immune
person, so the pathogen has no where to go, so it dies out
Problems with Vaccination Programmes?
vaccine does not work (dead form ineffective, pathogen hides from immune system)
vaccine not safe (no weak/inactive form, causes major side effects)
many strains of pathogen
cannot achieve herd immunity (logistic of vaccinating large proportion)
antigenic variability
What is antigenic variability?
the pathogen mutates, the antigen changes shape, so the memory cells no longer
complementary – do not recognise the pathogen.
What is a monoclonal antibody?
one type of antibody, complementary to one type of antigen, made by one type of plasma cell
What are monoclonal antibodies used for?
identify specific antigens or antibodies in person’s blood, or pregnancy tests
How do monoclonal antibodies identify specific antigens in the blood?
e.g. identify PSA antigen made by prostate cancer
place monoclonal antibodies complementary to PSA antigen on test plate
add person’s blood to test plate
if PSA antigen is present in the blood, it will bind to the monoclonal antibodies
then a 2nd set of monoclonal antibodies with an enzyme attached is added
if the PSA antigen is present, this 2nd set will bind to it
if the PSA antigen is not present, this 2nd set will not bind
the test plate is then washed
if PSA antigen is present, 2nd set of monoclonal antibodies will attach, this will not be washed away, so the
enzyme will be present
if PSA antigen not present, 2nd set of monoclonal antibodies will not attach, this will be washed away, so
enzyme also washed away
a colourless substrate is then added, if the enzyme is present it will breakdown the substrate causing a
colour change, if the enzyme is not present there will be no colour change
therefore: colour change occurs = enzyme present/PSA antigen is present, no colour change = no enzyme
present/no PSA antigen is present
How do monoclonal antibodies identify specific antibodies in the blood?
e.g. identify TB antibodies in the blood
place antigen complementary to TB antibodies on test plate
add person’s blood to test plate
if TB antibodies are present in blood, they will bind to the antigen
then a set of monoclonal antibodies (with an enzyme attached) complementary to the TB antibodies are
added
if the TB antibodies are present, the monoclonal antibodies will attach
if the TB antibodies are not present, the monoclonal antibodies will not attach
the test plate is then washed
if the TB antibodies are present, the monoclonal antibodies will attach, this will not be washed away, so
the enzyme will be present
if the TB antibodies are not present, the monoclonal antibodies will not attach, this will be washed away,
so the enzyme will be washed away
a colourless substrate is then added, if the enzyme is present it will breakdown the substrate causing a
colour change, if the enzyme is not present there will be no colour change
therefore: colour change occurs = enzyme present/TB antibody is present, no colour change = no enzyme
present/no TB antibody is present
How are monoclonal antibodies used in pregnancy testing?
Pregnant Women produce HCG Hormone in their Urine
Test Strip has 3 parts to it (1st: start contains antibodies complementary to HCG, 2nd: middle contains
antibodies complementary to HCG-Antibody complex, 3
rd: end contains antibodies complementary to
HCG Antibodies)
if woman is pregnant, HCG in the urine binds to antibodies on 1st part forming a HCG-Antibody complex,
the HCG-Antibody complex then binds to antibodies on the 2nd part forming a blue line (positive result),
HCG Antibodies also bind to 3rd part as a control
if woman is not pregnant, no HCG in urine so nothing binds to HCG Antibodies in 1st part, so nothing
binds to antibodies in 2nd part leaving no blue line (negative result), the HCG Antibodies still bind to 3rd
part for the control
What is HIV/AIDs?
HIV = Human Immunodeficiency Virus
AIDs = Acquired Immunodeficiency Syndrome
HIV is the Pathogen, AIDs is the Infectious Disease
HIV is spread by fluid to fluid contact (unprotected sexual intercourse, sharing needles, mother to child
via placenta or breast feeding)
HIV damages and destroys T Helper Cells, therefore person no longer produces Immune Response and
has no defence to against pathogens/infections = AIDs
With AIDs, individual at risk from all sorts of pathogens/infections called Opportunistic Infections
