Cell immunity COPY Flashcards
Describe the Direct ELISA test
Antibodies are bound to the bottom of the well in a well plate and are immobilised
A blood sample from the patient is inserted into the well
If the blood sample contains pathogen’s antigen, the antigen will bind to the antibody, as they are complementary in shape
The well is washed out to remove any unbound antigens
Add enzyme attached to antibodies
Antibodies with enzyme bind to antigen
wash out the well to remove unbound antibodies
the enzyme-substrate complex between the antibody with enzyme and antigen results in a colour change
Describe the Indirect ELISA test
Antigens are bound to the bottom of the well in a well plate and are immobilised
A blood sample from the patient is inserted into the well
If the blood sample contains antibodies, the primary antibody will bind to the antigen, as they are complementary in shape
The well is washed out to remove any unbound antibodies
Add enzyme attached to antibodies (secondary antibodies)
secondary antibodies bind to primary antibodies
wash out the well to remove unbound antibodies
solution changes colour
Why are control centres important in monoclonal antibody tests?
prevents false negative results since it shows that the antibodies (from the reaction site) which would bind to pathogen has moved up the strip
Why do we need to wash the wells thoroughly in between steps?
to prevent false positives
What are the ethical worries about using mice to produce monoclonal antibodies?
The mice are deliberately induced with cancer to grow tumours and produce antibodies, which will cause suffering despite guidelines trying to minimise this.
What are the ethical worries about the side effects from the use of monoclonal antibodies?
Rarely, death can occur in patients with multiple sclerosis, therefore it is important that patients know the risks and benefits of the drug before being taking it (informed consent).
What are the ethical worries about trialling new drugs?
can present dangers to the individual involved
After a disease is diagnosed, monoclonal antibodies are used in some medical treatments. Give one example of using monoclonal antibodies in medical treatments (3)
Targets pathogens
carries drug to specific cells
blocks antigens on cells
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why?
specific primary structure
specific tertiary structure
only binds to one antigen
What is the definition of immunity?
the ability of an organism to resist infection
What is passive immunity?
person given antibodies, these work then die, no long term immunity, no memory cells.
What is active immunity?
stimulation of the production of antibodies = direct contact with the pathogen or its antigen
the individual has memory cells – can make their own antibodies & provides long term immunity
takes a long time to develop
How does activity 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
How do vaccines produce effective immunity to disease?
- Administration of the antigen or weakened pathogen to activate Immune system
- causes immune response
- engulfed by a phagocyte (macrophage), then antigens present on cell surface membrane
- T cells with complementary receptor binds to the antigen, which activates T helper cells
- T cells divide by mitosis to form clones = memory cells
- secrete cytokines activate B cells with complementary antibodies in a process known as clonal selection
- B cells divide by mitosis to form a clone (clonal expansion)
- some form memory cells- remain in body = allows a more rapid and stronger secondary response
- No symptoms of the disease when exposed to real pathogen
What are the features of a successful vaccination programme (5)
- must be economically available in sufficient quantities to immunise most of the vulnerable population
- must be few side affects or this may discourage individuals in the population from being vaccinated
- means of producing, storing and transporting the vaccine must be available
- must be able to administer the vaccine properly with trained staff
- must be possible to to vaccinate the vast majority of the vulnerable population to produce 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, and is unable to replicate = destroyed
What are the problems with vaccination programmes? (6)
- the vaccine does not work (dead form ineffective, pathogen hides from the immune system by concealing themselves inside cells , or by living in places out of reach)
- vaccine not safe (no weak/inactive form, causes major side effects)
- cannot achieve herd immunity (logistic of vaccinating large proportion)
- antigenic variability = immunity shortlived
- many strains of the pathogen
- individuals may develop the disease immediately after vaccination but before their immunity levels are high enough to prevent it . These individuals may harbour the pathogen and reinfect others
Why are more than one injections of vaccines normally given? (3 )
more antigens = more memory cells = more antibodies/ antibodies produced quicker
What are vaccines?
a serum that contains dead or weakened pathogens, which stimulate the production of antibodies
What are the factors that should be considered before the drug can be used o patients with disease?
- dosage of drug
- cost of drugs
- how effective it is
- no serious side effects
Draw and label the structure of HIV. Explain each feature (what is the lipid envelope made from, what does the capsid have inside, what does reverse transcriptase and attachment do, what is the genetic material?) (6)
Attachment protein: allows HIV to attach to cells surface of T helper Cells
Reverse transcriptase: catalyzes the production of DNA from RNA and is needed for virus replication
Capsid: encloses two single strands of RNA and some enzymes
Genetic material: two single strands of RNA
lipid envelope: made from the membrane stolen from the cell membrane of the precious host cell
What does HIV stand for?
human immunodeficiency virus
Describe and explain the replication of HIV
- HIV circulates in the bloodstream and the attachment protein on the HIV binds to the CD4 receptors on the helper T cells
- Lipid envelope Protein fuses with the cell-surface membrane and the RNA and enzymes of HIV enter the helper T cell
- HIV reverse transcriptase converts the virus’s RNA into DNA
- This DNA moves into the T helper cell’s nucleus, it releases an integrase enzyme that inserts the viral DNA into the human DNA. The virus becomes incorporated into the hosts genetic material
- This DNA now codes for new viral proteins
- These are assembled to make a HIV virus
- HIV viruses break away from the helper T cell with a piece of its cell-surface membrane surrounding them which forms their lipid envelope
Why does it take many years for AIDS to develop?
Because HIV often goes into dormancy
How does HIV cause the symptoms of AIDS?
without helper T cells a person cannot stimulate antibodies or cytotoxic T cells = person is unable to produce an adequate immune response so they become susceptible to other infections and cancers
Why don’t antibiotics work on viruses?
Cells walls: antibiotics interfere with bacterial cell wall by preventing the production of muerin, so that when the water enters the bacteria, the weak walls are unable to withstand the pressure= cause the cell to burst
Viruses do not have cell walls, they have protein coats from host cell, so there are no sites where antibiotics can work
Metabolic pathways: antibiotics disrupt metabolic pathways and viruses don’t have their own metabolic pathway to disrupt as they use host cell’s metabolic pathways.
Also, due to replicating in the host cell, they are difficult to access = antibiotics cannot reach them.
How does HIV avoid being recognised and destroyed by lymphocytes?
by repeatedly changing its protein coat
