3.2.4 Cell recognition and the immune system 3 Flashcards
Human immunodeficiency virus (HIV)
Replication in helper T cells
Reason
-HIV replicates using host cells (helper T cells) as it doesn’t have the equipment (e.g. enzymes and ribosomes) to replicate on its own
Human immunodeficiency virus (HIV)
Replication in helper T cells
-HIV infects and eventually kills helper T-cells
└act as host cells for the virus
-Th cells send chemical signals that activate phagocytes, Tc cells and B cells= important in immune response
-people with HIV develop aid s when the number of Th cells reach a critically low level
Human immunodeficiency virus (HIV)
Replication in helper T cells
Process
-HIV attachment protein attachmes to receptor cell on the membrane of the host (helper T cell)
-capsid is released into cell
└releases genetic material (RNA) into cells cytoplasm
-reverse transcriptase used to make complimentary strand of DNA from viral RNA template
└double stranded DNA made and inserted into human DNA
-host cells are used to make viral proteins from viral DNA found within human DNA
-viral proteins assembled into new viruses
└bud from the cell and infect other cells
(host cell ruptures and dies following this process)
EQ: The virus (HIV) infects and kills T helper cells in the immune system.
State ways in which the lack of T helper cells will affect the functioning of the immune system
immune system unable to -reproduce enough T helper cells └to release cytokines └and stimulate B cells; └which would make plasma cells └and release antibodies └stimulate macrophages; └stimulate T killer cells; └so there would be no humoral response └and no memory cells would be made
Ways in which this virus (HIV) can be transmitted from person to person
- unprotected sexual intercourse
- reusing and sharing, needles
- blood transfusion / mixing blood
- child birth
- breast feeding
How HIV causes the symptoms of AIDS
immune system unable to -reproduce enough T helper cells └to release cytokines └and stimulate B cells; └which would make plasma cells └and release antibodies └stimulate macrophages; └stimulate T killer cells; └so there would be no humeral response └and no memory cells would be made
Symptoms of aids
- respiratory infections
- susceptible to infections like chronic diarrhoea, tuberculosis, other serious fatal infections
HIV
-HIV (human immunodeficiency virus) effects immune system
└eventually leads to AIDS (acquired immune deficiency syndrome) where immune system deteriorates then fails
└makes people more venerable to other infections like pneumonia
Why people with AIDS die because they are unable to produce an immune response to pathogens
- because people are infected by other pathogens
- which reproduce and cause disease
- which can damage cells
- and release toxins
- and the immune system can’t prevent or stop the events
why because HIV shows a lot of antigenic variability a vaccine might not be effective against HIV
-antigen on HIV changes
-so specific receptor no longer binds to new antigen
OR
-there are many different stands of HIV
-and it is not possible to make a vaccine for all antigens
Why antibiotics are ineffective against viruses
- antibiotics kill bacteria by targeting bacterial enzymes and ribosomes thus interfering with metabolic reactions (human enzymes and ribosomes are different so not affected)
- viruses don’t own enzymes and ribosomes, use their host cells
- antirviral drugs target the few virus specific enzymes that exist (e.g. inhibit reverse transcriptase in HIV)
Monoclonal antibody
-antibodies are produced from the same plasma cell
Benefits of inducing monoclonal antibodies
-scientific and medical value
└single type of antibody can be isolated and clones
-most successful cancer treatment so far
Monoclonal antibodies
Cancer treatment
- monoclonal antibodies specific to the antigens on cancer cells are produced
- antibodies given to a patient→ attach themselves to receptors on cancer cells
- block chemical signals that stimulate their uncontrolled growth
EQ: Explain how the monoclonal antibody would prevent the regulator protein from working
-the monoclonal antibody has a specific tertiary
└so is complementary to regulator protein
-it binds to and forms a complex with the regulator protein
-so the regulator protein would not bind to the receptor
└as is not complementary to receptor
The use of monoclonal antibodies
List
- targeting medication to specific cell types by attaching a therapeutic drug to an antibody
- medical diagnosis
EQ: Why are tests using monoclonal antibodies specific
- the specific primary structure leads to a specific tertiary structure
- which is only complimentary to one antigen
Monoclonal antibodies
Pregnancy tests
Pregnancy tests detect the hormone hCG found in the urine of pregnant women
-application area contains antibodies bound to a blue bead
└that are complimentary to the hCG protein
-when urine is applied to application area
└any hCG will bind to antibody on the beads →antigen antibody complex
-urine + beads move up test strip
-test strip contains immobilised hCG antibodies
└any hCG will bind to antibody on the test strip →antigen antibody complex
└test strip turns blue due to blue beads attached
-if no hCG present, beads pass through without binding
└=test strip won’t turn blue
-test strip
└shows test is working
Ethical issues associated with the use of vaccines
- vaccines tested on animals before humans
- unfair that unvaccinated people (no side effects) are protected by herd immunity
- if epidemic would be difficult to decide who would get it first
Ethical issues associated with the use of monoclonal antibodies
-animals used to produce the cells from which monoclonal antibodies are produced
The ELISA test
-enzymes linked to immunosorbent assay
-use antibody to detect presence and quantity of protein in sample
-extremely sensitive
└so can detect very small amounts of a molecule
The ELISA test
Purpose
-allows you to see if a patient has any antibodies/antigens to a certain antigen/antibody
└e.g. medical diagnosis to test for pathogenic infections (e.g. HIV)
└e.g. allergies (e.g. nuts, lactose)
The direct ELISA test
Process
Uses a single antibody that is complimentary to the antigen you are testing for
-antigens from a patient sample are bound to the inside of a well in a well plate
-a complimentary detection antibody with attached enzyme is added
-if complimentary the antibody will bind to the antigen and become immobilized
-well is washed, to remove any unbound antibody
-substrate solution is added to well
└if detection antibody is present, enzyme reacts with substrate → colour change (positive result)
The indirect ELISA test
Process
Example
Uses two different antibodies
Can be used to see if patient has HIV antibodies
-HIV antigen bound to the bottom of a well plate
-patient (blood) sample containing many different antibodies is added to well
└if any antibodies against HIV/ HIV specific antibodies (primary antibody) they will bind to the antigen and become immobilized
-well is washed, to remove any unbound primary antibody
-a secondary antibody with a specific enzyme attached is added to the well
└can bind to the primary antibody
-well is washed, to remove any unbound secondary antibody
└if no primary antibody to bind to, secondary antibody will also be washed away
-substrate solution is added to well
└if detection antibody is present, enzyme reacts with substrate → colour change (positive result)
└indicates the person has HIV specific antibodies in their blood and is infected with HIV
What can the ELISA test be used to detect?
HIV, pathogens of tuberculosis and hepatitis
